hb.diva-portal.org1234438/FULLTEXT01.pdf · i ABSTRACT Polyethylene terephthalate (PET) is the most used fibre in the textile industry. PET is also used in other products, e.g. soft-drink

Visiting adress: Skaraborgsvägen 3 Postal adress: 501 90 Borås Website: www.hb.se/ths

Thesis for the Degree of Master in Science with a major in Textile Engineering

The Swedish School of Textiles Report no. 2018.14.02 31

st of May 2018

Chemical and physical changes in

PET fibres due to exhaust dyeing

- Issues in thermo-mechanical recycling of dyed PET textiles

Frida Lindström

i

ABSTRACT Polyethylene terephthalate (PET) is the most used fibre in the textile industry. PET

is also used in other products, e.g. soft-drink bottles and food packaging. Approxi-

mately 60% of the globally produced PET is intended for production of textile

fibres and the demand for polyester fibres have steadily increased over the last

decade. Yet, most of the recycled PET fibres are produced from discarded bottles

and not discarded textiles even though the generation of textile waste is increasing

year by year. The importance of finding efficient recycling routes for discarded

PET textiles is obvious. In thermo-mechanical recycling the thermoplastic charac-

teristic of PET is utilized to re-melt and re-form PET waste into new valuable

products. Today, this is used for bottle-to-fibre recycling but not for fibre-to-fibre

recycling. The main research question asked in this Master thesis is if the process

of exhaust dyeing compromise the possibility to recycle PET textiles through re-

melt spinning. It is believed that PET degradation through hydrolysis may occur

during dyeing. The degradation behaviour of PET has been widely studied. How-

ever, degradation during exhaust dyeing has not been investigated.

The process parameters temperature, time and number of dyeing cycles have been

investigated. Also, possible effects of different auxiliary chemicals have been stud-

ied. Dyeing and characterisation of two PET fabrics with filaments of different titer

was performed in order to investigate if the filament titer is also a parameter to

consider.

Tensile testing and surface characterisation through demand absorbency test

showed that the filament titer seems to affect how the tensile and moisture related

properties change due to dyeing. Differential scanning calorimetry showed that the

crystallisation rate is affected by the dyeing process. This can be an effect of for-

mation of shorter PET chains during dyeing. The auxiliary chemicals have been

shown to be the most critical factor in changes of the crystallisation behaviour.

Fourier-Transform infrared spectroscopy indicated that chain scission has occurred

during dyeing.

The results have shown that the exhaust dyeing process causes changes in tensile

properties, moisture related properties, degree of crystallinity as well as crystallisa-

tion behaviour. DSC and FTIR results indicate chain scission. Based on the results

it cannot be concluded if the changes are large enough to compromise the possibil-

ity to recycle PET textiles thermo-mechanically. Further research is required in

order to correlate the observed changes with possible problems in thermo-

mechanical recycling of dyed PET textiles.

Key words: Polyethylene terephthalate, polyester, exhaust dyeing, auxiliary chem-

icals, degradation, hydrolysis, thermo-mechanical recycling, fibre-to-fibre recy-

cling, FTIR, DSC, tensile properties, demand absorbency test.

ii

POPULAR ABSTRACT Polyester is the most used fibre in the textile industry. Polyester is a synthetic ma-

terial and the actual name of the material used for most polyester textiles is poly-

ethylene terephthalate or PET. The same material is used for production of PET-

bottles. When labels on clothing and other textile products state “Recycled polyes-

ter” it is usually textile fibres made from discarded PET bottles. One way to create

recycled fibres is by turning the bottles into smaller pieces which can be melted.

From the melt PET fibres can be formed.

The recycling of bottles to fibres is one step towards a more sustainable production

of textiles. Another important step would be to recycle fibres back to fibres. The

question is why fibre-to-fibre recycling is not used when bottle-to-fibre recycling

has been successfully established. Since the material in PET bottles can be melted

and formed into fibres, it is thought that the material in textiles could also be turned

back into fibres through a similar method.

In this Master thesis it has been studied if the dyeing of PET textiles could cause

any problems in a future recycling process. It is believed that properties of the PET

fibres changes as the textile is being dyed. Testing showed that strength, stiffness,

and how the fabric absorbs water differ between un-dyed and dyed polyester fab-

rics. The changes depend on how the fabrics are dyed, dyeing temperature and how

many times the fabrics are dyed affects the changes. Also, what chemicals are used

during dyeing affects the changes.

The dyeing process does cause changes in the PET but these changes may be too

small to cause problems in a future recycling process. The result of this Master

thesis is only one piece in a larger context. Therefore more research is necessary to

connect these results with fibre-to-fibre recycling and potential problems in such a

process.

iii

ACKNOWLEDGEMENTS First of all I would like to thank my supervisor Anders Persson for initiating this

project and for patiently providing guidance along the way. Our discussions and

your input have been very helpful. I appreciate how you always believe in your

students, and how that motivates me to always try my best, thank you! I would like

to thank the technicians in the dyeing- and finishing lab at the Swedish School of

Textiles, Carin Backe, Ulrika Norén and Catrin Tammjärv, for all your help and

guidance. It has been a lot of fun working with you in the lab! Thank you, Ellinor

Niit, for valuable feedback and advices. I also want to thank the lab technicians at

the polymer lab and the chemistry lab at the University of Borås for showing and

helping me with all necessary equipment.

I want to thank F.O.V. Fabrics AB for providing fabrics and chemicals for this

project. And I want to specially thank Stefan Gustafson for providing valuable

information as well as great input to this project.

I want to thank my fellow students for being there throughout this process provid-

ing valuable feedback and discussions. But mostly, thank you for creating so many

moments of laughter even during challenging times.

Last but not least, I want to thank my family and friends for all of their support and

for always believing in me. And a special thanks to Milo for being the very best of

friends.

Frida Lindström

June 2018

iv

v

TABLE OF CONTENTS 1. Introduction ........................................................................................................ 1

1.1. Background ............................................................................................... 1

1.1.1. Polyethylene terephthalate ................................................................ 1

1.1.2. Polymerisation of PET ...................................................................... 2

1.1.3. Dyeing of PET .................................................................................. 4

1.1.4. Overview of recycling of PET .......................................................... 5

1.2. Problem description .................................................................................. 8

1.3. Scope and Research questions .................................................................. 9

1.4. Limitations ................................................................................................ 9

2. Literature Review ............................................................................................. 10

2.1. Degradation behaviour of PET ............................................................... 10

2.1.1. Hydrolytic degradation ................................................................... 10

2.1.2. Chemically induced degradation ..................................................... 13

2.1.3. Thermal degradation ....................................................................... 13

2.1.4. Degradation induced by photo radiation ......................................... 14

2.1.5. Enzymatically induced degradation ................................................ 15

2.2. PET oligomers ........................................................................................ 15

2.2.1. Oligomers and dyeing ..................................................................... 16

2.3. Side effects of dyeing and processing ..................................................... 16

2.4. Thermo-mechanical recycling of PET .................................................... 18

2.5. Polymer characterisation ......................................................................... 20

2.5.1. Molecular weight determination ..................................................... 20

2.5.2. Fourier-Transform Infrared spectroscopy ....................................... 21

2.5.3. Characterisation of the fine structure of PET .................................. 23

3. Materials and Methods ..................................................................................... 24

3.1. Materials ................................................................................................. 24

3.1.1. Sample preparation ......................................................................... 24

3.2. Experimental ........................................................................................... 25

vi

3.2.1. Exhaust dyeing ................................................................................ 27

3.2.2. Characterisation............................................................................... 28

3.3. Statistical analyses .................................................................................. 31

3.4. Data modification for graph construction ............................................... 31

4. Results .............................................................................................................. 32

4.1. Weight differences .................................................................................. 32

4.1.1. Weight differences due to dyeing.................................................... 32

4.1.2. Vacuum drying ................................................................................ 34

4.2. Tensile properties .................................................................................... 37

4.2.1. Breaking strength ............................................................................ 37

4.2.2. Elongation at break ......................................................................... 40

4.2.3. Young’s modulus ............................................................................ 42

4.3. Demand absorbency capacity and Moisture absorption rate ................... 45

4.4. Fourier-Transform Infrared spectroscopy ............................................... 51

4.4.1. Absorbance ratios ............................................................................ 55

4.5. Differential Scanning Calorimetry .......................................................... 59

4.5.1. DSC curves for PETC samples ........................................................ 64

4.5.2. DSC curves for PETM samples ........................................................ 67

4.6. Dissolving of PET fabrics ....................................................................... 70

5. Discussion and analysis .................................................................................... 71

5.1. Weight differences .................................................................................. 71

5.1.1. Vacuum drying ................................................................................ 72

5.2. Tensile properties .................................................................................... 73

5.3. Correlations and relationships ................................................................. 74

5.3.1. The effects of exposure time above Tg ............................................ 74

5.3.2. The effects of dyeing temperature ................................................... 74

5.3.3. DSC results, tensile properties and demand absorbency ................. 75

5.4. FTIR results ............................................................................................. 76

5.4.1. Trans-gauche relationships .............................................................. 79

vii

5.5. DSC results ............................................................................................. 79

5.6. Methodology ........................................................................................... 80

5.6.1. Demand absorbency test ................................................................. 80

5.6.2. DSC ................................................................................................. 81

5.6.3. FTIR ................................................................................................ 81

5.7. Recyclability of dyed PET fabrics .......................................................... 81

6. Conclusions ...................................................................................................... 83

7. Future research ................................................................................................. 85

7.1. Variety of processing conditions and materials ...................................... 85

7.2. Re-melt spinning of dyed fabrics ............................................................ 85

7.3. Further characterisation .......................................................................... 85

7.3.1. Characterisation of oligomers ......................................................... 86

Reference list .......................................................................................................... 87

Appendix I. Tukey test: Breaking strength for PETC .......................................... 93

Appendix II. Tukey test: Breaking strength for PETM ..................................... 94

Appendix III. Tukey test: Elongation at break for PETC ................................... 95

Appendix IV. Tukey test: Elongation at break for PETM .................................. 96

Appendix V. Tukey test: Young’s modulus for PETC ...................................... 97

Appendix VI. Tukey test: Young’s modulus for PETM ..................................... 98

Appendix VII. Tukey test: Demand absorbency capacity for PETC ................... 99

Appendix VIII. Tukey test: Maximum absorption rate for PETC ................... 100

Appendix IX. Tukey test: Demand absorbency capacity for PETM ................. 101

Appendix X. Tukey test: Maximum absorption rate for PETM ...................... 102

Appendix XI. FTIR spectra – PETC ................................................................. 103

Appendix XII. FTIR Spectra – PETM ............................................................... 106

Appendix XIII. Correlation analysis PETC ..................................................... 111

Appendix XIV. Correlation analysis PETM .................................................... 113

viii

1

1. INTRODUCTION The textile industry faces many problems related to sustainability and sustainable

development. Natural resources like fossil fuels, fresh water, and land areas are

exploited in order to produce textile fibres and textile products for several different

purposes. Fossil fuels are used as a source for energy in production plants as well

as a raw material for synthetic fibres. In dyeing and finishing of textiles huge

amounts of water, chemicals and energy are consumed. Despite this heavy con-

sumption of resources, mass produced textiles like clothing are produced at very

low costs and sold at low prices.

The world is facing the problem of increased consumption, and fashion and textile

goods are a part of this problem. As the consumption increases so does the waste.

Huge amounts of recyclable textiles and clothes find their way to landfills and in-

cineration meaning wastage of potentially valuable resources (Textile Exchange

2017). It is of great importance for the sustainable development within the textile

industry to create efficient and sustainable recycling routes that utilize the waste in

order to turn it into once again useful resources.

Polyester or more specifically polyethylene terephthalate (PET) is by far the most

used fibre in the textile industry today. According to Preferred Fiber & Materials

Market Report 2017 (Textile Exchange 2017) synthetic fibres held a market share

of about 68% of the total fibre market in 2016 and almost 80% of that share was

held by polyester. The largest application area for PET is textile fibres (ICIS 2007;

Park & Kim 2014). About 60% of the globally produced PET is intended to be

used for textile fibre production (Oekotex 2011; Park & Kim 2014; Plastic Insight

2017) yet recycling of PET textiles is not very common.

1.1. BACKGROUND According to Textile Exchange (2017) approximately 52 million tonnes of polyes-

ter fibres was produced during 2016, and even though the usage of recycled PET

(rPET) in the textile industry grew by 58% from 2015 to 2016 only 7% of the total

PET usage was estimated to be rPET. One great advantage of PET is its thermo-

plastic characteristic which creates a possibility to re-melt and spin recycled fibres

from discarded PET products, e.g. drinking bottles. This method may have the

potential to be used in recycling of PET textiles as well.

Dyeing is one important processing step in textile production that adds value to the

final product. As mentioned previously the processes for dyeing and finishing of

textiles consume very large volumes of water as well as chemicals and energy. At

the same time there is a risk that the textile is affected by the dyeing process, which

is likely to reduce the life span and probably the recyclability of the textile.

1.1.1. POLYETHYLENE TEREPHTHALATE

Polyesters are a group of polymers containing ester linkages in the backbone chain

and the polymers within this category can be classified as aliphatic or aromatic

(Albertsson, Edlund & Odelius 2012). PET is an aromatic polyester of thermo-

plastic nature with a characteristic glass transition temperature (Tg) and melting

2

point (Tm). The thermoplastic characteristic can be utilized both in production and

recycling processes (Grishanov 2011). Tg and Tm depend on different factors, e.g.

molecular weight (MW) and degree of crystallinity, and can therefore vary be-

tween different PET products. According to Albertsson, Edlund and Odelius (2012

pp. 253) Tg of PET is approximately 74°C and Tm is approximately 265°C. Accord-

ing to Cowie and Arrighi (2008 pp. 423) PET used for fibre forming purposes have

a Tg of approximately 70°C and a Tm around 265°C. The fine structure of PET can

be explained by a two-fraction or a three-fraction model. The former consider that

PET consists of one crystalline fraction and on amorphous fraction while the latter

consider three fractions. The three fractions are suggested to be the crystalline frac-

tion, the mobile/randomly organised amorphous fraction, and the rigid/organised

fraction (Burkinshaw 2015; Badia, Strömberg, Karlsson & Ribes-Greus 2012).

The repeating unit in PET is ethylene terephthalate and it is shown in Figure 1. For

general application textile fibres the average number of units in one PET chain is

100 and the average MW is about 20 000. Higher MW result in stronger fibres

(Venkatachalam et al. 2012). The MW of PET differs depending on the final appli-

cation.

The polymerisation process affects the intrinsic viscosity of the final PET polymer

(Farah, Kunduru, Basu & Domb 2015). Textile-grade PET has an intrinsic viscosi-

ty of 0.40 – 0.70 dl/g while PET for carbonated soft drinks has an intrinsic viscosi-

ty of 0.73 – 0.85 dl/g (Awaja & Pavel 2005; Gupta & Bashir 2005, see Farah et al.

(2015) pp. 144). The intrinsic viscosity is related to the MW and both of these

properties are important in thermo-mechanical recycling.

FIGURE 1 REPEATING UNIT IN POLYETHYLENE TEREPHTHALATE

1.1.2. POLYMERISATION OF PET

PET is polymerised through condensation polymerisation, a type of step-growth

polymerisation in which the reactions lead to elimination of small molecules or

condensation products, e.g. water (Albertsson, Edlund & Odelius 2009; Cowie &

Arrighi 2008). In the case of PET there are different possible polymerisation

routes. Most common is polymerisation from ethylene glycol and terephthalic acid

(TPA) or dimethyl terephthalate (DMT). The two different polymerisation routes

are shown in Figure 2 and Figure 3. The polymerisation reactions are equilibrium

reactions, meaning possibilities for reversible reactions to take place, e.g. hydroly-

sis which is further explained in section 2.1.1. Hydrolytic degradation. This means

that the condensation products have to be removed to avoid de-polymerisation

reaction to take place and in order to achieve high molecular weights (Albertsson,

Edlund & Odelius 2009).

3

FIGURE 2 STEP-GROWTH POLYMERISATION OF PET USING TPA AND ETHYLENE GLYCOL

FIGURE 3 STEP-GROWTH POLYMERISATION OF PET USING DMT AND ETHYLENE GLYCOL

4

1.1.3. DYEING OF PET

Due to the highly crystalline nature of PET fibres and the rigidity in the polymer

chains elevated pressures and high temperatures should be used in order to success-

fully dye PET textiles (Grishanov 2011). The crystallinity of the PET fibres makes

it difficult for dye molecules to penetrate the fibres at temperatures below 100°C

(Richards 2015). The dye type most commonly used for dyeing of PET fibres and

textiles is disperse dyes (Grishanov 2011; Burkinshaw 2015) and the dominating

method for dyeing PET with disperse dyes is high temperature dyeing (Burkinshaw

2015). High temperature dyeing is carried out under pressure in temperatures be-

tween 130°C and 140°C. In addition to the high temperature dyeing method carrier

dyeing and dry-heat fixation or thermosol method can be used for dyeing of PET

fibres (Burkinshaw 2015; Roy Choudhury 2011). Pressurised dyeing machines,

e.g. jet machines, are the most commonly used dyeing equipment for PET (Clark

2011). Dyeing is usually followed by clearing treatments with detergent or through

reductive or oxidative treatments. The aim of this is to remove residuals dye stuff

and auxiliary chemicals (Burkinshaw 1995).

Exhaust dyeing with disperse dyes

Exhaust dyeing is a discontinuous process that is being used for different fibre

types. Dyeing can be carried out on fibres, yarns or fabrics. In the case of exhaust

dyeing of PET fibres and textiles with disperse dyes, the dye is dispersed in a dye

bath and the textile material is immersed into the bath (Bellini, Bonetti, Franzetti,

Rosace & Vago 2006). The temperature is raised to 130-140°C so that the dye stuff

can access the interior of the fibres.

Exhaust dyeing has been described as a four stage process with the following four

stages by Bellini et al. (2006):

I. Dispersion of dye in dye bath

II. Adsorption of dye molecules from dye bath onto fibre surface

III. Diffusion from fibre surface into fibre interior

IV. Migration for even dye concentration throughout the fibre

Gulrajani (2008) described exhaust dyeing as a three stage process consisting of a

sorption phase, a diffusion phase, and a levelling phase.

Disperse dyes and auxiliary chemicals

A disperse dye is defined as “a substantially water-insoluble dye having substan-

tivity for one or more hydrophobic fibres, e.g. cellulose acetate, and usually ap-

plied from fine aqueous dispersion” (The Society of Dyers and Colourists (UK) see

Roy Choudhury (2011) p. 47). Disperse dyes are suitable for dyeing of PET fibres

since PET is hydrophobic and therefore not easily dyed with water-soluble dyes.

Disperse dyes have a very low solubility in water, that is increased with increasing

temperature and also by the use of dispersing agents (Burkinshaw 2015). Dispers-

ing agents are used in mixture with disperse dyes with the aim to ease dispersion of

the dye in the aqueous dye bath. For this purpose the dispersing agent and the dye

are milled together to achieve a suitable particle size and particle size distribution

of the dye. The role of the dispersing agent during milling is to prevent agglomera-

5

tion. Also, the dispersing agent plays a vital role in maintenance of a stable disper-

sion during dyeing. Additional dispersing agent can be added directly into the dye

bath with the purpose of stabilising the dispersion, improving the dye-to-fibre mi-

gration, and levelling during dyeing at high temperatures (ibid.). Dispersing agents

consist of different chemical compounds, some examples are naphthalene sulphon-

ic acid, 1-naphtol 6-sulphonic acid, and fatty alcohol-ethylene oxide condensate

(Chakraborty 2010).

Levelling agents are used in dyeing of PET and their role is to facilitate migration

of the disperse dyes from aqueous phase to fibre and to improve the levelling be-

haviour (Burkinshaw 2015; Roy Choudhury 2011). Anionic and non-ionic level-

ling agents are used in the dyeing of PET. The function of the anionic levelling

agent is to improve migration to and diffusion in the fibre. The function of non-

ionic levelling agents is to improve levelling by retarding the dye uptake (Burkin-

shaw 2015).

1.1.4. OVERVIEW OF RECYCLING OF PET

Polymer waste can be recycled, used for energy recovery (incineration) or end up

in landfills (Ragaert, Delva & Van Geem 2017). Two important reasons behind

recycling are to prevent wastage of useful materials and to reduce the consumption

of valuable raw materials (Vadicherla & Saravanan 2014). According to Park and

Kim (2014) recycling of PET is desirable since it will lead to reduced CO2 emis-

sions and oil usage. Another important reason for recycling is that PET degrades

very slowly in natural conditions so recycling is a way to take care of PET waste

(Awaja & Pavel 2005). Recycled PET can be used for production of e.g. bottles,

packaging and fibres. In both USA and EU the largest end market share for rPET

in 2009 was fibres. However, these market shares have decreased during 2001-

2009 in favour for increased application of rPET in bottles and food packaging

(Welle 2011).

Generally, recycling of plastic waste is closed-loop recycling or open-loop recy-

cling (Ragaert, Delva & Van Geem 2017). PET bottles recycled into textile fibres

is an example of open-loop recycling while recycling of textile fibres into textile

fibres is an example of closed-loop recycling.

Mechanical recycling

One great advantage of PET that is often mentioned in the literature is the thermo-

plastic characteristic that creates a possibility for recycling through re-melting. In

case of PET textiles recycling from fibres to fibres can theoretically be achieved

through re-melt spinning, meaning that PET fibres are melted and the melt is ex-

truded into new fibres. However, this is not yet established as a recycling method

for PET textiles.

The steps in mechanical recycling of PET differ based on the type and quality of

waste. Post-industrial waste and post-consumer waste requires different recycling

routes (Ragaert, Delva & Van Geem 2017). A general overview of the steps in

mechanical recycling of post-consumer waste is presented in Figure 4.

6

FIGURE 4 GENERAL OVERVIEW OF THE MECHANICAL RECYCLING PROCESS OF POST-

CONSUMER PET-WASTE

The most commonly used mechanical recycling method for production of rPET

fibres is melt extrusion of PET flakes from PET bottle waste directly into fibres.

The other method involves a middle step, namely conversion of the PET flakes into

granulates or pellets before melt extrusion into fibres (Park & Kim 2014). Today,

mechanical recycling of PET-bottles is well-established and discarded bottles are

mostly recycled into fibres or other packaging products. Two challenges in me-

chanical recycling of PET are degradation during the re-processing and degrada-

tion that have occurred during the lifetime of the PET product (Ragaert, Delva &

Van Geem 2017).

A more extensive review on thermo-mechanical recycling of PET is presented in

section 2.4. Thermo-mechanical recycling of PET.

Chemical recycling

Chemical recycling is achieved through depolymerisation of the PET polymers

through glycolysis, hydrolysis, methanolysis, or aminolysis reactions (Park & Kim

2014; Ragaert, Delva & Van Geem 2017). In addition ammonolysis and hydro-

henation can be utilized in chemical recycling of PET (Ragaert, Delva & Van

Geem 2017). The different methods result in different monomers, oligomers or

other chemicals (Al-Sabagh, Yehia, Eshaq, Rabie & ElMetwally 2015; Ragaert,

Delva & Van Geem 2017). An overview of chemical recycling processes and the

resulting products is presented in Figure 5.

Guo, Lindqvist and de la Motte (2018) presented a recycling route for PET into

bis(2-hydroxyethyl) terephthalate monomers (BHET) through glycolysis. By intro-

ducing a pre-degradation step before depolymerisation it was shown that the effi-

ciency of recycling PET into BHET can be enhanced. The efficiency depends on

the type of catalyst used in the pre-degradation step. BHET is used as a source in

re-polymerisation reactions back to PET (ibid.). BHET can also be used for manu-

facturing hydrophobic disperse dyes or acrylic and allylic monomers (Ragaert,

Delva & Van Geem 2017).

7

FIGURE 5 OVERVIEW OF CHEMICAL RECYCLING ROUTES AND RECYCLED PRODUCTS FOR

PET WASTE

Polyols can be used for condensation polymerisation of e.g. polyurethanes and

epoxy resin. Terephthalic acid (TPA) and dimethyl terephthalate (DMT) can both

be used for polymerisation of PET. Diamides of TPA can be used for several dif-

ferent products, e.g. for plasticiser in polyvinyl chloride (PVC) (Ragaert, Delva &

Van Geem 2017).

Difficulties in PET recycling

Post-consumer waste can be difficult to recycle since the waste stream is very

complex and the waste is usually contaminated. Degradation products, contamina-

tions and different residues from production and usage can cause problems in PET

recycling. During the usage phase PET products are exposed to different conditions

that may lead to degradation, e.g. UV radiation, oxygen, and mechanical stresses

(Park & Kim 2014). Contaminants like PVC and adhesives used for labels can

produce acids during the recycling process. Some acids, e.g. acetic acid, rosin acid

and abietic acid, act as catalysts in chain scission reactions that occur during re-

processing. Dyes and colourants are also considered to contaminate the waste (Al-

Sabagh et al. 2015; Awaja & Pavel 2005). Acetaldehyde is a by-product from deg-

radation reactions that occur in PET. This contaminant is problematic since it can

migrate from PET packages into food and drinks (Awaja & Pavel 2005).

Water can create big problems in mechanical recycling since even very low mois-

ture content causes hydrolysis of the polymer in the molten state (Al-Sabagh et al.

2015). Hydrolysis of PET result in an increase of carboxyl end-groups, meaning

increased hydrophilicity (Zimmerman & Kim 1980). Since moisture is problematic

in re-melting of PET this can obviously be problematic in a potential recycling

step, since the ability to retain moisture will increase if the PET is hydrolysed.

Another difficulty in recycling is maintaining constant quality between the rPET-

batches, since the quality and the properties of the waste will affect the final prop-

erties of the rPET. Due to thermal and thermal-oxidative degradation during the

recycling process the mechanical properties are negatively affected. The colour of

the rPET can also be affected due to degradation (Venkatachalam et al. 2012).

Degradation and side effects due to re-processing will be further described in sec-

tion 2.3 Side effects of dyeing and processing.

8

1.2. PROBLEM DESCRIPTION Virgin PET (vPET) is mostly made from crude oil, a fossil raw material source

likely to be exhausted in a foreseeable future. By using rPET instead of vPET the

dependence on oil as a raw material is reduced (Park & Kim 2014). Recycling is of

great importance when it comes to satisfying the future fibre demand in a more

sustainable way. In order to develop efficient routes and methods for recycling of

textiles the knowledge field regarding the waste that is intended to be recycled

needs to be broadened.

PET recycling using discarded bottles and packages as the main resource is today

well established. A large share of rPET from these sources ends up as fibres. How-

ever, this share has decreased over the years because more and more rPET is used

for production of bottles and packaging (Welle 2011). The largest application area

of vPET is textile fibres and the generation of textile waste is assumed to increase

globally within the near future. This waste could potentially serve as a source for

production of rPET fibres through thermo-mechanical recycling. The question is

why thermo-mechanical fibre-to-fibre recycling is not yet applied, while bottle-to-

fibre recycling is a well-established method. This Master thesis focuses on if and

how dyeing may affect thermo-mechanical recycling of PET textiles.

The exhaust dyeing process is widely used to dye PET textiles in form of both

yarns and fabrics. Aside from obvious sustainability problems related to dyeing of

textiles there are risks of damaging or partly degrading the fibres during dyeing. In

extent, this could affect both the quality of the textile product as well as the possi-

bility to recycle the textile when discarded as waste. Degradation of PET has been

widely studied, however degradation studies considering temperatures and time

relevant for dyeing are limited.

During exhaust dyeing the PET polymers are exposed to aqueous steam at tem-

peratures above Tg, usually about 130°C, for a considerable time. Significant hy-

drolysis occurs in PET when it is exposed to aqueous environments at temperatures

above Tg (McIntyre 1985 see Allen, Edge & Mohammadian 1991), so it seems that

during exhaust dyeing there is a risk of hydrolysing the PET textiles. It has been

suggested that treatment at temperatures above Tg after the primary crystallisation

affects degree of crystallinity (Gupta & Kumar 1981a) and mechanical properties

of PET fibres (Gupta & Kumar 1981c). Auxiliary chemicals are important for suc-

cessful outcomes in PET dyeing. For pH-regulating of the bath compounds con-

taining acetic acid is used, and as mentioned previously acetic acid is one of the

most harmful and problematic contaminants causing problems in thermo-

mechanical recycling of PET (Al-Sabagh et al. 2015; Awaja & Pavel 2005).

Recelj, Gorenšek, and Žigon (2002) studied quality and quantity of oligomers ex-

tracted from PET textiles due to treatment at elevated temperatures. It was found

that the amount of PET oligomers consisting of 6-10 repeating units and more than

10 repeating units increased after treatment of the textiles. Based on this it was

concluded that during treatment at elevated temperatures hydrolysis of PET textiles

occur.

9

1.3. SCOPE AND RESEARCH QUESTIONS The aim of this Master thesis is to study possible side effects on the PET polymer

due to exhaust dyeing from aqueous phase under conventional acidic conditions. In

extent the consequences of these side effects will be related to the possibility for

PET textiles to be thermo-mechanically recycled.

The work takes off in the following hypothesis: The polymer structure of PET is

affected by the exhaust dyeing process to such an extent that re-melt spinning is

compromised. The polymer is exposed to water and chemicals for a considerable

time and that environment can possibly cause hydrolysis and chemical reactions,

and thereby the polymer could be degraded. In extent, this is also believed to affect

the possibility to mechanically recycle polyester textiles through re-extrusion.

Based on the hypothesis the overall focus of this thesis project is to investigate

what kind of chemical and/or physical changes that occur in PET due to exhaust

dyeing and if any dyeing parameters can be identified as critical. The parameters to

be addressed in this project are:

I. Dyeing temperature

II. Dyeing time (at dyeing temp.)

III. Bath composition (auxiliary chemicals)

IV. No. of dyeing cycles (related to both time and auxiliary chemicals)

V. Filament titer

To fulfil the aim of this Master thesis the following research questions are to be

answered:

- Is the polymer structure of PET affected by exhaust dyeing? If so, how is

the polymer structure affected? Can any dyeing parameters be identified

as critical?

- Are the tensile properties of PET affected by exhaust dyeing? If so, how

are the properties affected and which dyeing parameters are critical?

- Are the surface characteristics of PET affected by exhaust dyeing? If so,

how are the properties affected and which dyeing parameters are critical?

- Are any changes induced by the exhaust dyeing process related to fila-

ment titer?

- Can changes induced by exhaust dyeing negatively affect the possibility

to recycle PET textiles through a thermo-mechanical process?

1.4. LIMITATIONS This Master thesis is limited to study possible side effects of exhaust dyeing with

disperse dyes and common auxiliary chemicals on PET. Other dyeing processes

and dye types are excluded from this study. Dyeing is limited to dyeing of fabrics,

and not yarns or fibres. Textiles consisting of 100% PET are investigated in this

Master thesis, textiles made from material blends are excluded. There are different

types of polyesters used for textiles and among them PET is the by far the most

extensively used and therefore this thesis work will focus on PET only. Other pro-

cesses as well as the usage phase can possibly interfere in thermo-mechanical recy-

cling of textiles but that will not be investigated in the frame of this Master thesis.

10

2. LITERATURE REVIEW The literature review covers different degradation behaviours and mechanisms of

PET, which could affect the possibility for recycling. Literature regarding side

effects induced through processing of PET and PET textiles is presented. Also,

literature regarding mechanical recycling of PET is covered.

2.1. DEGRADATION BEHAVIOUR OF PET Degradation will affect several characteristics of a polymeric material. Chemical

composition, chain conformation, MW, MW distribution, and crystallinity are

characteristics affected by degradation (Venkatachalam et al. 2012). For example

McMahon, Birdsall, Johnson and Camilli (1959) observed changes in crystallinity

of PET due to hydrolysis and reduced tensile strength in PET fibres due to degra-

dation. Allen, Edge and Mohammadian (1991) also observed changes in crystal-

linity due to hydrolysis of PET. Changes in chain conformation and chemical com-

position on the surface of rPET pellets due to degradation induced by UV radiation

have been observed (Al-Azzawi 2015).

Awareness and knowledge regarding degradation mechanisms are of great im-

portance when considering recycling of textile materials. Throughout both pro-

cessing and usage the materials are exposed to different conditions which can lead

to degradation. Different types of degradation occur in PET, the main types being

thermal degradation, oxidative degradation, and hydrolytic degradation. Degrada-

tion can also be induced by photo radiation, enzymatically catalysed reactions,

chemical reactions, and mechanical stresses (Venkatachalam et al. 2012).

2.1.1. HYDROLYTIC DEGRADATION

Hydrolysis is defined as “a double decomposition reaction with water as one of the

reactants” (Britannica Academic 2016). Degradation occurs as the polymer is hy-

drolysed, in extent when the polymer reacts with water molecules. In the case of

PET reaction with water molecules result in chain scission of the polymer chain at

the ester linkage which cleaves the polymer. This process is schematically shown

in Figure 6. A reaction with one water molecule will break one ester linkage in the

polymer (Venkatachalam et al. 2012; Park & Kim 2014).

FIGURE 6 HYDROLYSIS AND RESULTING MOLECULES WITH HYDROXYL AND CARBOXYL END

GROUPS, BASED ON VENKATACHALAM ET AL. (2012) AND PARK AND KIM (2014)

11

Carboxyl end-group concentration has proven to be related to the rate of hydrolysis

and the hydrolysis is described as an autocatalytic process driven by the end-group

concentration (e.g. Zimmerman & 1980; Ravens & Ward 1961; Sammon, Yarwood

& Everall 2000). Zimmerman and Kim (1980) showed that the hydrolytic degrada-

tion of PET is an autocatalytic reaction in which the rate of hydrolysis is dependent

on the carboxyl end-group concentration. Increasing carboxyl end-group concen-

tration leads to increased rate of hydrolysis. Also, there is a relationship between

the initial carboxyl end-group content and the rate of formation of carboxyl end

groups. A higher initial content will result in faster hydrolysis of the polymer

(ibid). Sammon, Yarwood and Everall (2000) concluded that the hydrolysis of

amorphous PET in pure water is an autocatalytic process. Through Fourier-

Transform Infrared spectroscopy (FTIR) of hydrolysed thin PET films it was

shown that the number of hydrophilic end-groups increases as hydrolysis progress-

es, which provides conditions for autocatalysis. The analysis showed that hydroly-

sis of PET result in hydroxyl end-groups and carboxyl end-groups (as shown in

Figure 3).

Hosseini et al. (2007) studied hydrolytic degradation of fibre-grade PET with the

purpose of showing how this process can be a problem during washing of PET

textiles. By exposing PET chips to hydrolytic conditions the authors showed that

the intrinsic viscosity (IV) and MW decreases as the retention time increases. The

carboxyl end-group concentration increased with increased retention time.

According to Venkatachalam et al. (2012) hydrolytic degradation of PET is 10 000

times faster than thermal degradation in temperatures between 100°C and 120°C.

McMahon et al. (1959) showed that in PET yarns hydrolysis is much more domi-

nant than thermal degradation as well as thermo-oxidative degradation, in tempera-

tures between 70°C and 90°C. By exposing amorphous PET sheet materials to dif-

ferent temperatures and humidity conditions Allen, Edge and Mohammadian

(1991) concluded that hydrolysis is the most dominant degradation process in PET

in temperatures between 70°C and 90°C. It was shown that hydrolysis leads to

changes in degree of crystallinity and these changes depend on both temperature

and humidity percentage in the surrounding atmosphere (ibid.).

It has been shown in several studies that PET hydrolysis occur when exposed to

aquatic or humidity conditions at temperatures above Tg. Several studies on PET

hydrolysis in temperatures between 50°C and 100°C have been published, e.g.

Sammon, Yarwood and Everall (2000), Pirzadeh, Zadhoush and Haghighat (2007),

and Burgoyne and Merii (2007) among others. Studies concerning PET hydrolysis

at temperatures in the interval used in high temperature dyeing (130°C-140°C)

have not been found. Also, it is common that hydrolysis and degradation over a

long period of time is investigated, e.g. from five up to 28 days (Pirzadeh,

Zadhoush & Haghighat 2007) and up to 500 days (Allen, Edge & Mohammadian

1991). These periods of time are much longer than the exposure times in the dyeing

processes of PET.

Hydrolysis of PET textiles

Burgoyne and Merii (2007) presented a comprehensive study on hydrolysis of two

PET yarns with different carboxyl end-group concentrations. Tensile strength and

12

elongation at break of PET yarns was affected by hydrolysis in 50, 70, and 85°C in

aqueous environment (pH 7). Loss in breaking strength was found for all tempera-

tures in the two PET yarns, and the largest loss was observed in samples hydro-

lysed at 85°C. Initial carboxyl end-group concentration plays a vital role in the

extent of hydrolysis. After 130 days of exposure to aqueous conditions in 85°C

breaking strength had decreased from 85.5 N to 58.4 N (31.75%) for the lower

carboxyl end-group concentration and from 82.3 N to 40.2 N (51.15%) for the

higher carboxyl end-group concentration. Increases in elongation at break were

also observed. (ibid) Hydrolysis in acidic conditions (pH 4), aqueous conditions

(pH7), and alkali conditions (pH 11) at 70°C also resulted in decreased breaking

strength and increased elongation at break. The exposure times were between 190

and 197 days. No significant differences between the conditions were found. Also

in these conditions the end-group concentration was found to affect the outcome,

leading to higher extent of hydrolysis for the yarn with higher initial carboxyl end-

group concentration (ibid.).

Pirzadeh, Zadhoush and Haghighat (2007) investigated the effects of temperature

and humidity conditions on hydrolysis of fibre-grade PET granules and PET yarns.

Exposure to water in 60, 70, 80, and 87°C for 28 days showed that granules and

yarns were hydrolysed to a higher extent when exposed above Tg (87°C). It was

suggested that temperature plays a more vital role than moisture content in hydrol-

ysis of fibre-grade PET granules and PET yarns. It has been suggested that hydrol-

ysis of PET occur in the amorphous fractions. By investigating hydrolysis in PET

yarns with different orientations and different degree of crystallinity Pirzadeh,

Zadhoush and Haghighat (2007) concluded that the degree of crystallinity strongly

influences hydrolysis. A higher degree of crystallinity acts as prevention to hydrol-

ysis.

Alkaline hydrolysis at temperatures below Tg is suggested to act on the surface of

the fibre causing changes in how PET yarns and PET fabric interact with water.

Through wicking tests it has been shown that water transportation of yarns and

fabrics is affected by hydrolysis, leading to improved water transportation (Sanders

& Zeronian 1982). Hydrolysed PET fabrics more easily transport water from the

fabric surface to the fabric interior than reference fabrics. Sanders and Zeronian

(1982) suggested that alkaline hydrolysis at 60°C results in increased porosity and

spacing between fibres and this affects the capillary forces behind the water trans-

portation. This is also suggested to increase the ability to hold water in the fabric.

According to Sanders and Zeronian (1982) it is difficult to detect hydrolysis based

on moisture regain determination. Weight increase due to moisture absorption was

shown to not differ particularly between untreated and hydrolysed samples.

According to Burkinshaw (1995 pp. 1-2) hydrolysis of PET “is of relatively little

significance even under high-temperature dyeing conditions (130°C) provided that

the pH is maintained within the range of 4.5 to 6.” Other than this no information

on hydrolysis during dyeing has been found. Dyeing and potential side-effects are

presented in 2.2 Side-effects of dyeing and processing.

13

Chemicrystallisation

It is suggested that hydrolysis occur in the amorphous phases of the polymer.

Chain cleavage result in shorter polymer chains and increased mobility of these

chains creates possibilities for the chains to rearrange from an entangled structure

to a more ordered one. This provides conditions for chemicrystallisation, which

means that the chains from the amorphous phase align and contribute to the crystal-

line phase (Allen, Edge & Mohammadian 1991).

2.1.2. CHEMICALLY INDUCED DEGRADATION

As explained in 1.1.2. Polymerisation of PET, molecules like water and ethylene

glycol can cause de-polymerisation of PET. Chemically induced degradation or de-

polymerisation reactions are used for chemical recycling of PET (Ragaert, Delva &

Van Geem 2017). Several different chemical compounds can be used for the pur-

pose of de-polymerisation.

Ethylene glycol, di-ethylene glycol, and propylene glycol can de-polymerize PET

through a process called glycolysis. It has been shown that the degree of de-

polymerisation by ethylene glycol is affected by the presence of catalysts (Baliga

& Wong 1989).

Methanol can be used for de-polymerisation of PET back to the monomers dime-

thyl terephthalate and ethylene glycol. The methanol breaks the ester linkages in

the PET chain during leading to de-polymerisation. De-polymerisation by the use

of methanol is called alcoholysis (Dutt & Soni 2013).

Shukla & Harad (2006) showed that PET can be depolymerised through aminolysis

using ethanolamine generating bis(2-hydroxy ethylene)terephthalamide (BHETA).

Ethanolamine causes de-polymerisation by attacking the ester linkages in the PET

chain.

2.1.3. THERMAL DEGRADATION

Thermal degradation is degradation induced by elevated temperatures in the ab-

sence of oxygen. The mechanism behind thermal degradation is chain scission of

the PET polymer (Jabarin & Lofgren 1984; Venkatachalam et al. 2012). The ther-

mal degradation of PET is illustrated in Figure 7. As can be seen in the figure,

chain scission due to thermal degradation results in vinyl ester end-groups with an

unsaturated carbon-carbon bond.

14

FIGURE 7 THERMAL DEGRADATION AND RESULTING MOLECULES WITH VINYL ESTER END

GROUP AND CARBOXYL END GROUP, BASED ON VENKATACHALAM ET AL. (2012) AND PARK

AND KIM (2014).

Thermo-oxidative degradation

Just as thermal degradation thermo-oxidative degradation is induced by elevated

temperature, but as indicated by name this type of degradation involves reactions

with oxygen (Venkatachalam et al. 2012).

Jabarin and Lofgren (1984) investigated short-term thermal and thermo-oxidative

degradation of PET in the temperature range 275°C to 350°C. Weight and inherent

viscosity are more affected by thermo-oxidative degradation than thermal degrada-

tion in the presence of nitrogen. This was shown to be the case in different melt

temperatures and for different exposure times. Also, it was shown that the drying

conditions and melting conditions in terms of atmosphere conditions plays a vital

role in thermal and thermo-oxidative degradation of PET. Drying before melting is

very important, since hydrolytic degradation occur quickly upon melting in pres-

ence of moisture. In addition to this, drying condition is of great importance to

avoid degradation in the PET melt. PET pellets dried in air exhibit greater weight

loss and decrease in inherent viscosity due to degradation in the melt, compared to

vacuum dried pellets (ibid.). This is very important when considering re-melt spin-

ning of PET textiles.

2.1.4. DEGRADATION INDUCED BY PHOTO RADIATION

Gok (2016) investigated the role of photo radiation and humidity on degradation of

PET. It was shown that chain scission is the main degradation mechanism affecting

the properties of the degraded PET. Also, changes in the degree of crystallinity

were observed after degradation and this was also proposed to affect the properties.

It was suggested that crystallinity increases due to the formation of shorter chains,

with an increased mobility so crystallisation is facilitated.

Al-Azzawi (2015) proposed that degradation of rPET induced by UV radiation is a

surface effect. It was suggested that UV radiation affects the structure of rPET,

leading to a more random structure due to degradation. This was shown to result in

decreased mechanical properties, changes in spectral data, and changes in thermal

behaviour.

15

2.1.5. ENZYMATICALLY INDUCED DEGRADATION

Enzymes and enzyme treatments have been investigated for the purpose of modify-

ing PET fibres and textiles. Lee and Song (2010) studied if and under what condi-

tions cutinase and lipase could be used to change the hydrophilicity of PET fabrics.

The role of the enzymes is catalyse hydrolysis of the ester linkages in PET chains

in the fabric surface and thereby cause an increase of hydrophilic carboxyl and

hydroxyl end-groups and in extent an increase in hydrophilicity.

The enzyme cutinase can be used for hydrolysing of PET. This was investigated

and compared to alkaline hydrolysis by Donelli, Freddi, Nierstrasz and Taddei

(2010). It was shown that both amorphous and crystalline PET films can be hydro-

lysed using cutinase but the degradation mechanism is different depending on the

fine structure of the films. Enzymatically induced hydrolysis was shown to result

in increased hydrophilicity.

2.2. PET OLIGOMERS PET oligomers of different shape and size exist in PET as residuals from the

polymerisation process. Also, oligomers in PET can be formed as a result of pro-

cessing (Cimecioglu, Zeronian, Alger & Collins 1986). Characteristics and content

of oligomers in bottle-grade PET flakes obtained from post-consumer bottles was

investigated by Dulio, Po, Borrelli, Guarini and Santini (1994). The recycled PET

flakes were exposed to heat treatment in vacuum and/or extrusion before character-

isation of oligomers. High performance liquid chromatography (HPLC), size ex-

clusion chromatography (SEC), and desorption chemical ionization/mass spectra

(DCI/MS) were used for the characterisation. It was shown that the concentration

of cyclic trimer (oligomer with three ethylene terephthalate units) in the heat treat-

ed and extruded samples were very similar to the concentration in the untreated

PET flakes. Larger oligomers, both cyclic and linear, were identified in the samples

after extrusion, and the content seemed to be affected by the extrusion temperature

as well as processing time. Dulio et al. (1994) suggested that the larger oligomers

are decomposition products formed during re-processing.

Cimecioglu et al. (1986) observed migration of oligomers to the PET fibre surface

upon exposure to methylene chloride vapour. Cyclic trimers as well as oligomers

of higher degree of polymerisation (DP) were observed on the fibre surface. It was

suggested that oligomers, mainly the cyclic trimers, crystallise during heat treat-

ment of PET fabrics at 200°C. Moisture regain of extracted oligomers and PET

fibres differ after heat treatment. The cyclic oligomers exhibited lower moisture

regain than the fibres and it is suggested that this is due to the crystalline nature of

the oligomers (ibid.).

Connections between oligomer content and alkaline hydrolysis in PET fibres have

been demonstrated by Collins and Zeronian (1992). Hydrolysis in aqueous sodium

hydroxide (NaOH) and methanolic NaOH causes formation of oligomeric species.

HPLC showed a larger content of oligomers in fabrics treated in methanolic NaOH,

indicating that process conditions will affect oligomer content. The MW distribu-

tion of the oligomers was higher in methanolic NaOH treated PET than in aqueous

NaOH treated PET. Oligomer was clearly present on the surface of hydrolysed

PET fibres, which was shown through scanning electron microscopy (SEM) (ibid.).

16

Hydrolysis in methanolic and aqueous NaOH causes weight loss of PET. Collins

and Zeronian (1992) also demonstrated weight loss as a result of extraction of oli-

gomers by two different solvents. Surface oligomers could be extracted by per-

chloromethane and residual perchloromethane and remaining oligomers could be

extracted by chloroform.

2.2.1. OLIGOMERS AND DYEING

The nature of the PET oligomers decides if they are problematic during dyeing or

not. Linear oligomers are partially soluble in water and thereby these oligomers do

not cause problems in dyeing. Cyclic oligomer, however, exhibit a very low solu-

bility in water as well very high crystallisation rates and thereby these oligomers

create problems in dyeing (Burkinshaw 1995; Recelj, Gorenšek & Žigon 2002).

The oligomers can affect the surface properties of PET fibres if the oligomers mi-

grate to the fibre surface. During dyeing the temperature is above Tg and this in-

duces flexibility to the polymer chains which facilitate migration of oligomers

from the interior of the fibre to the surface of the fibre (Recelj, Gorenšek & Žigon

2002). When considering dyeing of PET fibres, the cyclic oligomers are the most

problematic and should be kept below 0.5 weight percentage (Dulio et al. 1994).

Recelj, Gorenšek and Žigon (2002) showed that the quantity of oligomers present

after dyeing was affected by the processing conditions. It was shown that the quan-

tity of oligomers after dyeing in acidic conditions (pH 4.5-5) increases as the dye-

ing temperature increases. The quantity of oligomers on dyed PET fabrics can be

reduced by using alkaline pre-treatment before acidic dyeing or by dyeing in alka-

line conditions (ibid.).

There are different methods to reduce the quantity of cyclic oligomers in PET after

dyeing, as well as from the machines. One method is to dye in alkaline conditions

instead of acidic conditions. This is suggested to hydrolyse the oligomers (Recelj,

Gorenšek & Žigon 2002). Different types of surfactants have been shown to reduce

the amount of cyclic oligomers in dyed fibre surfaces (Vavilova, Prorokova & Ka-

linnikov 2003). Also, reduction clearing can be used to remove oligomers from

dyed PET fabrics (Burkinshaw 1995).

2.3. SIDE EFFECTS OF DYEING AND PROCESSING Gulrajani, Saxena and Sengupta (1979) studied if and how PET stress-strain char-

acteristics changes due to dyeing with disperse dyes. It was found that the elastic

modulus of PET filaments at initial strain, approximately below 8%, differed be-

tween dyed and un-dyed samples but the samples exhibited the same stress-strain

behaviour at higher stresses until breaking. The modulus was higher for the dyed

samples than for the untreated samples. The authors speculated that the difference

in elastic modulus could be an effect of mechanical hindrance provided by the dye

molecules or due to formation of hydrogen bonds between dye molecules and pol-

ymers. By investigating a second disperse dye the first speculation was stated to be

the most likely reason behind the change in elastic modulus (ibid.). In a second

study Gulrajani, Saxena and Sengupta (1980) further investigated possible mechan-

ical hindrance provided by disperse dye molecules. Also, possible structural

changes in the polymer due to dyeing were investigated by measuring critical dis-

solution time (CDT). It was expected that mechanical hindrance, structural chang-

17

es, or a combination of the two could affect the mechanical properties of dyed pol-

yester fabrics (ibid.). Recelj, Gorenšek and Žigon (2002) observed changes in

breaking stress and elongation at break due to dyeing. Breaking stress and elonga-

tion at break for the warp yarn was shown to increase after dyeing in acidic condi-

tions. However, elongation at break for the weft yarn decreased. This indicates that

changes depend on the yarn type. The authors do not state differences between

warp and weft yarns.

Smole and Zipper (2002) compared the effects of dyeing from different treatment

media on the supramolecular structure of PET. Supercritical CO2 dyeing, conven-

tional water dyeing, and hot air thermo-fixation dyeing was studied. The tempera-

ture used for all treatments was 130°C. Dyeing was carried out for 60 minutes. The

PET was dyed in form of yarn. According to Smole and Zipper (2002) all investi-

gated dyeing processes lead to increased crystalline regions of the samples. The

crystallite size of the crystals that contribute to the increase depends slightly on the

dyeing treatment media and treatment temperature. The crystallinity increase due

to supercritical CO2 dyeing was estimated to be around 20%. For the water dyeing

and hot air thermo-fixation dyeing the crystallinity increase was smaller. Density

increases were observed due to all the treatment. The largest increase was observed

due to supercritical CO2 dyeing (1.3881 g/cm3 to 1.4001 g/cm

3) and the smallest

increase was observed due to water dyeing (1.3881 g/cm3 to 1.3961 g/cm

3). It was

not shown whether the observed changes were statistically significant or not, but

the authors claim that the changes induced by the treatments do not have any ef-

fects on the mechanical properties of the PET fibres. The investigated treatments

resulted in a decrease in MW and DP. The water dyeing resulted in the smallest

changes. The average MW was decreased from 21750 (untreated) to 20050 and the

average DP decreased from 108 to 99 due to water dyeing. This was calculated

based on intrinsic viscosity measurements (ibid.).

The effects of heat setting on various properties of PET have been studied. Gupta

and Kumar (1981a) demonstrated how heat setting temperature and heat setting

time affect the degree of crystallinity. Heat setting temperatures between 100°C

and 220°C was investigated and heat setting time was between 1 and 60 minutes.

Heat setting was performed on multifilament PET yarns in silicone oil bath. Tem-

perature was suggested to affect the degree of crystallinity, the higher the heat set-

ting temperature the higher degree of crystallinity was observed. On the other

hand, degree of crystallinity showed a more complex time-dependence. Heat set-

ting of fibres in the time interval 1 to 20 minutes was shown to result in increased

degree of crystallinity. In the time interval 20 to 60 minutes, decreased degree of

crystallinity was observed. The authors explain that this may be an effect of im-

provement of the perfection of the crystalline structure in the PET fibres. This was

suggested to occur due to the heat treatment after the primary crystallisation and

due to diffusion of dislocations, vacancies and chain ends from the crystalline

phase into the amorphous phase. With increased treatment time the degree of crys-

tallinity can therefore be reduced. Gupta and Kumar (1981a) suggest that heat

treatment in a taut state can improve the orientation of the polymers in the crystal-

line phase. Taut state being a state when the PET yarns are exposed to heat treat-

ment stretched to a constant length.

18

Heat treatment above Tg after primary crystallisation have been shown to affect the

Young’s modulus of multifilament PET yarns. When samples were exposed to heat

treatment in taut state smaller differences in Young’s modulus was detected com-

pared to differences detected in samples treated in relaxed state (Gupta & Kumar

1981b). In this case, the PET yarns were either exposed to heat treatment in a re-

laxed state or in a taut state at a constant length (Gupta & Kumar 1981a). Based on

this, Gupta and Kumar (1981b) suggested that the Young’s modulus of a multi-

filament PET yarn is more affected by the orientation of the polymers rather than

the degree of crystallinity. Samples heat set in taut state was found to exhibit a

higher Young’s moduli, indicating correlation between the increased orientation

and higher moduli. Heat treatment above Tg in a taut and relaxed state was shown

to result in decreased orientation of the polymers present in the amorphous phase,

the decrease being larger when heat treated in a relaxed state (Gupta & Kumar

1981a). According to Gupta and Kumar (1981b) Young’s moduli seem to be more

dependent on treatment temperature than exposure time.

Gupta and Kumar (1981c) discussed the role of the interface between crystalline

and amorphous phases on the tensile properties of PET. Samples exposed to heat

treatment in taut condition exhibited higher Young’s moduli and higher yield point

than samples treated in relaxed condition. The reason behind this was proposed to

be differences in distribution of strain. Due to different interphases between crys-

talline and amorphous regions in the differently treated samples the strain distribu-

tion is expected to differ. If there is a sharp interphase, hence a sharp transition

between the phases, the distribution of strain is thought to be less uniform than if

there is a smooth transition between the phases (ibid.). The elongation at break was

observed to increase due to heat treatment in relaxed condition, and the increase

was supposedly dependent on the treatment temperature. The heat treatment in

relaxed state resulted in shrinkage of the filaments and decreased orientation (Gup-

ta & Kumar 1981a) and this was suggested as a reason behind the changes of elon-

gation at break. Tenacity showed similar dependence on treatment temperature as

elongation at break. Gupta and Kumar (1981c) claim that exposure time of heat

treatment does not significantly affect elongation at break or tenacity, it is rather

the degree of orientation that these properties depend on.

2.4. THERMO-MECHANICAL RECYCLING OF PET It is important to point out that no information on thermo-mechanical fibre-to-fibre

recycling has been found. However, several authors mention that one of the great

advantages of PET products in general is that they can be recycled through re-

melting due to its thermoplastic nature (e.g. Venkatachalam et al. 2012; Park &

Kim 2014).

It has been shown that thermo-mechanical recycling of PET result in changes of

different properties. Thermal and mechanical properties are affected by recycling

(Torres, Robin & Boutevin 2000; López et al. 2014). Melt viscosity and average

MW has also been shown to be affected by mechanical recycling (Assadi, Colin &

Verdu 2004; López et al. 2014).

Injection moulding causes thermo-mechanical degradation in rPET from bottle

scraps. Compared to injection moulded vPET (bottle-grade), injection moulding of

19

rPET results in a more brittle material with lower average MW and intrinsic viscos-

ity (Torres, Robin & Boutevin 2000). Decreased MW and intrinsic viscosity due to

injection moulding of rPET has also been observed by López et al. (2014). Accord-

ing to Torres, Robin and Boutevin (2000) the decrease in intrinsic viscosity makes

rPET from bottles suitable for fibre production.

According to Assadi, Colin and Verdu (2004) extrusion of rPET flakes obtained

from bottles lead to both reversible and irreversible changes of the polymer. The

reversible changes are said to be caused by hydrolysis or transesterification reac-

tions. The irreversible changes are said to be dependent on the presence of oxygen

during extrusion. In absence of oxygen random chain scission causes irreversible

changes during re-extrusion. In presence of oxygen the irreversible changes are

claimed to be caused by radical chain oxidation of the methylene (CH2) groups in

the PET chain. Assadi, Colin and Verdu (2004) showed that the oxygen pressure

and the exposure time are critical factors for how the MW changes during re-

processing of rPET.

Based on the three-fraction model Badia et al. (2012) studied how multiple injec-

tion moulding cycles affect the fine structure and in extent the mechanical proper-

ties of bottle-grade PET and rPET (recycled from bottle-grade PET). DSC results

showed that the percentage of the mobile amorphous fraction decreases while the

percentage of the rigid amorphous fraction increases as a result of increased num-

ber of injection moulding cycles. The authors suggest that this is due to chain scis-

sion of the polymers in the mobile amorphous fraction that occur due to degrada-

tion during re-processing. Chain scission result in shorter chains and these chains

can more easily re-arrange and organise and thereby contribute to the rigid amor-

phous phase (ibid.). This behaviour called chemicrystallisation has also been sug-

gested to occur in PET when exposed to hydrolysis by others (Hosseini et al. 2007;

Sammon, Yarwood & Everall 2000). López et al. (2014) observed through DSC

that rPET (bottle-grade) reprocessed by injection moulding crystallise faster than

vPET. The vPET samples exhibited slow crystallisation rate which emerged as

very wide crystallisation peaks upon cooling. The heat of crystallisation [J/g] was

almost twice as high in re-processed samples compared to virgin samples. López et

al. (2014) suggested that this is due to the chain scission that occurs during re-

processing.

Dulio et al. (1994) suggested that recycling of bottle-grade PET through extrusion

result in formation of PET oligomers. The extrusion temperature seems to be vital

for the size of the oligomers formed. In extent, this can affect further processing of

rPET products, e.g. dyeing.

Awaja and Pavel (2005) presented an overview on requirements that post-

consumer PET in form of flakes must meet for successful re-processing to be pos-

sible. Intrinsic viscosity should be higher than 0.7 g/dl, melting temperature should

be higher than 240°C, and the moisture content should be kept below 0.02wt%.

Also, requirements regarding the concentration of contaminants like dye and PVC

are presented.

20

According to Welle (2011) thermo-mechanical recycling of PET bottles is well-

established. rPET from bottles are used for different products, e.g. bottles and fi-

bres. Over the years methods involved in the thermo-mechanical recycling of PET

have been developed and studied with the aim to improve different properties of

the rPET-products. Different modifiers that can be added during re-processing have

been studied, e.g. functionalised polypropylene (Oromiehie & Mamizadeh 2004)

and chain-extender (Makkam & Harnnarongchai 2014). Mixing of rPET and vPET

and the ratios between the two have also been researched (Lee, Lim, Hahm & Kim

2012; Oromiehie & Mamizadeh 2004).

Oromiehie & Mamizadeh (2004) compared the final properties of rPET,

rPET/vPET-blends, and rPET/vPET-blends containing functionalised polypropyl-

ene. It was shown that the MW and the mechanical properties depend on the

weight percentage of rPET used in blends. Also, crystallinity has been suggested to

depend on the weight percentage of rPET used in blends. Crystallinity increases

has been observed as the percentage of rPET increases in rPET/vPET-blends. Since

MW was lower in rPET it was argued that crystallisation occur more easily than in

vPET.

To obtain good enough fibres rPET can be mixed with vPET. The fractions of

vPET and rPET (from discarded bottles) in fibres affect thermal and mechanical

properties. The crystallisation behaviour and more specifically the crystallisation

rate has been shown to increase in fibres with higher fraction of rPET (Lee et al.

2012).

Contaminants like acids and dye stuff in post-consumer PET are mentioned to

cause difficulties in thermo-mechanical recycling (e.g. Awaja & Pavel 2005; Ven-

katachalam et al. 2012). It has been shown that disperse dyes can be extracted from

dyed PET fabrics by using the solvent 1,3 Dimethyl-2-Imidazolidinone (DMI)

(Andersson Drugge & Svensson 2016). It has also been claimed that the solvent

dimethyl sulfoxide (DMSO) can be used for removal of dye from PET textiles

(Wu, Wu, Wang & Gan 2014). It has not been investigated if extraction of dye by

DMI or DMSO results in changes of the polymer. Gupta, Bandi, Mehta & Schiraldi

(2007) demonstrated that material from coloured PET bottles could be bleached

using hydrogen peroxide before thermo-mechanical recycling. It was shown that

this method results in decreased intrinsic viscosity and the intrinsic viscosity de-

pends on how bleached the material is.

2.5. POLYMER CHARACTERISATION In this part of the literature review different methods for polymer characterisation

are described in the context of characterisation of PET. The review of FTIR is fo-

cused on characterisation of changes related to degradation.

2.5.1. MOLECULAR WEIGHT DETERMINATION

Several different methods are used for MW determination of polymers. The differ-

ent methods result in different average molecular weights. Some methods will also

be useful for investigating polydispersity (Albertsson, Edlund & Odelius 2009).

21

SEC is one of the most commonly used methods for determining MW and MW

distribution of polymers (Albertsson, Edlund & Odelius 2009). It has been demon-

strated that gel permeation chromatography (GPC) which is a form of SEC can be

used for PET. However, this method can be somewhat problematic since PET is

difficult to dissolve in commonly used solvents in room temperature (Farah et al.

2015).

One important method used for determination of MW is through measuring intrin-

sic viscosity. This can be measured in solution or determined by measuring melt-

flow index (MFI) (Farah et al. 2015). Al-Azzawi (2015) used MFI measurements

to determine the MW of rPET before and after photo degradation.

Du, Yang and Xie (2014) studied if FTIR with an attenuated total reflectance ac-

cessory (ATR) would be a proper method for investigation of hydrolytic degrada-

tion in PET by correlating FTIR-ATR results with MW changes measured by vis-

cometry. The ratio between carboxylic acids and esters was investigated and relat-

ed to the extent of hydrolysis.

2.5.2. FOURIER-TRANSFORM INFRARED SPECTROSCOPY

FTIR is a vibrational spectroscopic technique that uses infra-red radiation. When a

sample is exposed to radiation the molecules vibrate depending on how they absorb

the radiation. The type of vibration (e.g. wagging, rocking and bending) depends

on e.g. configuration, conformation and orientation in the sample (Siesler 2012).

FTIR have been used for investigations of hydrolysis (Sammon, Yarwood & Ever-

all 2000; Du, Yang & Xie 2014), degradation during thermo-mechanical recycling

(Badia et al. 2012), degradation induced by UV radiation (Al-Azzawi 2015), and

surface modification of PET (Donelli et al. 2010).

The absorbance of amorphous PET and semi-crystalline PET differs, therefore

some specific peaks can be identified as crystalline marker bands and other peaks

can be identified as amorphous marker bands. Several important bands in the infra-

red spectrum of PET that depends upon the crystallinity of the polymer have been

established (Miayke 1959). When the crystallinity of PET increases the CH2 rock-

ing of the ethylene glycol changes from a gauche conformation (amorphous) to

trans conformation (crystalline). This has been observed to cause an intensity in-

crease in the infrared spectrum at wavenumber 848 cm-1

and an intensity decrease

at 895 cm-1

. Miyake (1959) claim that changes in crystallinity should be studied by

investigating intensity of wavenumber that form trans-gauche couples, like 848

cm-1

-895 cm-1

. Other trans-gauche couples that can be related to other types of

vibration that have been suggested are 1456 cm-1

and 1453 cm-1

; 1337 cm-1

and

1370 cm-1

; and 973 cm-1

and 1042 cm-1

(ibid.). Donelli et al. (2010) suggested

1341, 972, and 849 cm-1

to be crystalline marker bands and 1371, 1044, and 898

cm-1

to be amorphous marker bands based on FTIR characterisation of amorphous

and semi-crystalline PET films.

Sammon, Yarwood and Everall (2000) observed spectral changes in PET films due

to hydrolysis. Two peaks in between 2800 and 3000 cm-1

was found to emerge due

to hydrolysis. These peaks were presented to be associated with chain scission

leading to shorter chains and formation of carboxyl and hydroxyl end-groups.

22

Changes in the absorbance at wavenumber associated with the carbonyl bonds have

been observed as a result of hydrolysis (Sammon, Yarwood & Everall 2000) and

hygrothermal degradation (Chen, Hay & Jenkins 2012). Sammon, Yarwood and

Everall (2000) showed that the intensity of the absorbance peak related to the car-

bonyl bonds (C=O) decreases as a result of hydrolysis of PET film. Donelli et al.

(2010) showed that the intensity of the peak related to the carbonyl bonds de-

creased after hydrolysis induced by enzymes. The absorbance associated with the

carbonyl bonds have also been shown to be affected by photo degradation (Al-

Azzawi 2015; Gok 2016). Gok (2016) concluded that chain scission induced by

photo radiation and hydrolytic conditions result in intensity decrease of the peak at

the (C=O) associated wavenumber (1711 cm-1

).

Chen, Hay & Jenkins (2012) studied how infrared spectral data changes due to

crystallisation of PET. Due to increased crystallinity, intensity decrease at 1572

cm-1

and 1578 cm-1

and intensity increase at 1502 cm-1

and 1508 cm-1

were report-

ed. Absorbance changes at several other wavenumbers have also been reported.

In Table 1 wavenumbers of importance for characterisation of PET that have been

found in the literature are summarized. It is shown in the table what can be investi-

gated through absorbance at different wavenumber.

TABLE 1 WAVENUMBERS WITH CORRESPONDING ASSIGNMENTS SUMMARISED FROM THE

LITERATURE.

Wavenumber

(cm-1

)

Assignment Comment References

793 - Normalising reference

peak

Smole and Zipper (2002)

845 - 849 CH2 rocking Trans ethylene glycol

(crystalline)

Miyake (1959)

Badia et al. (2012)

Donelli et al. (2010)

Awaja and Pavel (2005)

898 – 899 CH2 rocking Gauche ethylene glycol

(amorphous)

Miyake (1959)

Badia et al. (2012)



973

975

C-O stretching Trans

(crystalline)



Gok (2016)

Miyake (1959)

1040 – 1044 C-O stretching Gauche

(amorphous)



1099 C-O stretching Gauche

(amorphous)

Miyake (1959)

1340

1341

1343

CH2 wagging Trans ethylene glycol

(crystalline)



Gok (2016)

1370

1371

1376

CH2 wagging Gauche ethylene glycol

(amorphous)

Miyake (1959)


Al-Azzawi (2015)


1410 - Normalising reference

peak




1453 CH2 bending Gauche ethylene glycol

(amorphous)

Miyake (1959)

1456 CH2 bending Trans ethylene glycol

(crystalline)

Miyake (1959)

23

1471 C-H bending Crystalline marker band Badia et al. (2012)


1610 – 1685 C=O Arises from carboxylic

acid formation

Du, Yang and Xie (2014)

1711 – 1719 Carbonyl bonds

C=O

Crystalline phase: 1718

Amorphous phase: 1725

Al-Azzawi (2015)


Gok (2016)

3550 O-H Polymeric bonded OH-

end-group

Badia et al. (2012)

2.5.3. CHARACTERISATION OF THE FINE STRUCTURE OF PET

The crystallinity in PET can be investigated by using FTIR spectroscopy. This was

done by Sammon, Yarwood and Everall (2000) whose result indicated changes in

the degree of crystallisation in PET film due to hydrolytic degradation. The eth-

ylene glycol group in the PET backbone chain have different conformations in the

crystalline and in the amorphous phases, and this result in differences in a FTIR

spectrum. In the amorphous phase the ethylene glycol group can have trans or

gauche conformation. In the crystalline phase the ethylene group can only have

trans conformation (Miyake 1959; Burkinshaw 2015). As stated previously this

affects the absorbance of infra-red radiation.

Badia et al. (2012) investigated how re-processing by means of injection moulding

affect the crystalline, rigid amorphous, and mobile amorphous fraction of bottle-

grade PET. DSC was used to determine the percentage of the different fractions. It

was suggested that degradation of PET through chain cleavage occur in the mobile

amorphous fraction during re-processing. Due to the degradation in this fraction

the residual chains can re-organise into rigid amorphous fraction. This was sug-

gested to be the reason behind changes in viscoelastic and mechanical properties

that were observed after re-processing. It was observed that the mobile amorphous

fraction decreases as the number of re-processing cycles increase and as an effect

the elastic behaviour of PET was negatively affected. The Young’s modulus of the

virgin PET was after five re-processing cycles decreased from approximately 1400

MPa to 1300 MPa. The strain at break decreased from approximately 350% to

20%. The stress at break decreased from approximately 44 MPa to 18 MPa (ibid.).

It is important to highlight that the processing temperature differ a lot from that of

dyeing and the polymer is exposed to degradation in the molten state.

Based on DSC results the degree of crystallinity can be calculated using Equation 1

(Badia, Vilaplana, Karlsson & Ribes-Greus 2009; Albertsson, Edlund & Odelius

2012 pp. 226)):

Equation 1

From the DSC results melting enthalpy or heat of melting can be obtained.

The assumed value, , for perfect crystalline PET is 140 J/g (Badia et al. 2009).

24

3. MATERIALS AND METHODS In the upcoming sections materials and methods used for the experimental study

are described in detail.

3.1. MATERIALS Polyester fabrics, dye stuff and auxiliary chemicals were provided by F.O.V. Fab-

rics AB, Borås Sweden. In Table 2 important properties of the two PET weaves

used in the study is presented. Two different weaves have been used for this study,

one conventional PET weave (further called PETC) and one microfibre PET weave

(further called PETM).

TABLE 2 PROPERTIES OF THE POLYESTER FABRICS USED IN THE STUDY.

Property PETC PETM

Area weigh (g/m2) 146,7 117,3

Yarn type warp Multifilament Multifilament

Yarn type weft Two-thread multifilament Multifilament

Titer warp yarn 167 dtex 110 dtex

No. of filaments in warp

yarn

48 144

Filament titer warp yarn 3.48 dtex 0.69 dtex

Titer weft yarn 334 dtex 76 dtex

No. of filaments in weft

yarn

96 144

Filament titer weft yarn 3.48 dtex 0.53 dtex

Fixation Heat set, 190°C Heat set, 180°C

Optical brightener No No

The dye used in the study was Teratop Blue HL-B 150%, which is an anthraqui-

none dye. Neutracid BO 45 was used for pH regulation of the dye baths. The level-

ling agent used was Egasol UP and the dispersing agent used was Lyocol RDN.

3.1.1. SAMPLE PREPARATION

Fabric duplicates with a size of 20 cm × 15 cm (warp × weft) were cut out from the

polyester weaves using a heat cutter hot knife. This cutting method was chosen in

order to obtain stable edges to minimise the risk of unravelling during dyeing. Four

reference duplicates from each weave was randomly picked. The fabric duplicates

were numbered from 1 to 140 (for PETC and PETM respectively) and by randomi-

sation the fabric duplicates were assigned to a certain sample. The aim of this was

to minimise systematic errors. Randomisation was performed in Excel.

25

3.2. EXPERIMENTAL The following five parameters were decided to be investigated in the experimental

part of this Master thesis:

I. Dyeing temperature

II. Dyeing time (at dyeing temp.)

III. Bath composition (auxiliary chemicals)

IV. No. of dyeing cycles (related to both time and auxiliary chemicals)

V. Filament titer

Table 3 summarizes the values that were decided to be used for each of the five

parameters.

TABLE 3 VARIED PARAMETERS AND CHOSEN VALUES.

Parameter Values

Dyeing tempera-

ture

105°C, 120°C or 135°C

Dyeing time 30, 60 or 180 minutes

Bath composition 1) Dye stuff, pH regulator

2) Dye stuff, pH regulator, levelling agent

3) Dye stuff, pH regulator, levelling agent, dispersing agent

No. of dyeing

cycles

1, 3 or 5

- For 105°C and 135°C

- 30 and 60 min

- Bath composition 3

Filament titer 3.48 dtex or 0.69 dtex

Based on the parameters and values 35 different combinations (further called sam-

ples) were decided to be used for the study. Table 4 summarises how the values

were coded to give the sample names. The sample names with corresponding pa-

rameter values are presented in Table 5. The reference samples are further called

PETC Ref and PETM Ref. All samples were prepared using PETC and PETM, which

is presented initially in the code (e.g. PETCT1p30). Dye stuff was included in all

dye baths and is therefore not included in the coding. The exposure time above Tg

depends on dyeing time and dyeing temperature. To calculate the exposure time

above Tg the heating time, dyeing time and cooling time has been added. This is

schematically shown in Figure 8. The higher the dyeing temperature, the longer the

heating and cooling time will be.

TABLE 4 VALUES AND CORRESPONDING CODING FOR SAMPLES.

Value Coding

Conventional PET PETC

Microfibre PET PETM

105°C T1

120°C T2

135°C T3

Dye + pH p

Dye + pH + levelling agent l

Dye + pH + levelling agent + dispersing agent d

26

TABLE 5 SAMPLE NAMES AND CORRESPONDING PARAMETER VALUES.

Sample

name

Dyeing

temp.

Bath

composition

Dyeing

time

No. of

dyeing cycles

Exposure time

above Tg

T1p30 105°C p 30 1 55

T1l30 105°C l 30 1 55

T1d30 105°C d 30 1 55

T1d30×3 105°C p 30 3 165

T1d30×5 105°C l 30 5 275

T1p60 105°C p 60 1 85

T1l60 105°C l 60 1 85

T1d60 105°C d 60 1 85

T1d60×3 105°C d 60 3 255

T1d60×5 105°C d 60 5 425

T1p180 105°C p 180 1 205

T1l180 105°C l 180 1 205

T1d180 105°C d 180 1 205

T2p30 120°C p 30 1 67.5

T2l30 120°C l 30 1 67.5

T2d30 120°C d 30 1 67.5

T2p60 120°C p 60 1 97.5

T2l60 120°C l 60 1 97.5

T2d60 120°C d 60 1 97.5

T2p180 120°C p 180 1 217.5

T2l180 120°C l 180 1 217.5

T2d180 120°C d 180 1 217.5

T3p30 135°C p 30 1 80

T3l30 135°C l 30 1 80

T3d30 135°C d 30 1 80

T3d30×3 135°C p 30 3 240

T3d30×5 135°C l 30 5 400

T3p60 135°C p 60 1 110

T3l60 135°C l 60 1 110

T3d60 135°C d 60 1 110

T3d60×3 135°C p 60 3 330

T3d60×5 135°C l 60 5 550

T3p180 135°C p 180 1 230

T3l180 135°C l 180 1 230

T3d180 135°C d 180 1 230

27

FIGURE 8 GENERAL EXHAUST DYEING PROFILE SHOWING HOW EXPOSURE TIME ABOVE TG

HAVE BEEN CALCULATED .

3.2.1. EXHAUST DYEING

Dyeing was carried out in the laboratory machine Pyrotec 2000 from Roaches. The

Pyrotec 2000 uses infrared heat to reach the required treatment temperature. Two

fabric duplicates were dyed in each beaker. A fabric/liquor ratio of 1:10 was used.

After dyeing the fabrics duplicates were rinsed in hot water, then in cold water, and

last in running cold water. Soft tap water was used for dyeing and rinsing. For the

fabric duplicates dyed three and five times no rinsing between the dyeing cycles

was performed. The dye bath was exchanged before every dyeing cycle.

The dyeing recipes that were used for PETC and PETM are shown in Table 6 and

Table 7, respectively. Weight percentage of chemicals and dye stuff is calculated

as weight percentage of the fabric weight. The dyeing recipes are based on infor-

mation provided by F.O.V Fabrics AB, Borås Sweden. The dye baths was prepared

in bigger volumes (1.5 litres at a time) to avoid systematic errors. An analytical

scale with a resolution of 0.1 mg was used to weigh the chemicals. The dye was

first dispersed in hot tap water after which the auxiliary chemicals were added.

After this the required amount of tap water was added to reach the total bath vol-

ume.

TABLE 6 DYEING RECIPE FOR PETC

Dye/Chemical Function Amount Total

amount

Teratop Blue HL-B 150% Dye 0.5wt.% 0.045 g

Neutracid BO 45 pH regulator 1.5 g/l 0.135 g

Egasol UP Levelling agent 1.8wt.% 0.162 g

Lyocol RDN Dispersing agent 1 g/l 0.09 g

Fabric/Liquor ratio:

1:10 Fabric weight:

9 g

(two duplicates)

Total

volume:

90 ml

28

TABLE 7 DYEING RECIPE FOR PETM

Dye/Chemical Function Amount Total

amount

Teratop Blue HL-B 150% Dye 0.5wt.% 0.035 g

Neutracid BO 45 pH regulator 1.5 g/l 0.105 g

Egasol UP Levelling agent 1.8wt.% 0.11 g

Lyocol RDN Dispersing agent 1 g/l 0.07 g

Fabric/Liquor ratio:

1:10 Fabric weight:

7 g

(two duplicates)

Total

volume:

70 ml

3.2.2. CHARACTERISATION

Area weight, tensile test, and water absorption demand test were chosen for charac-

terisation in order to indicate possible changes in properties due to exhaust dyeing.

FTIR and DSC were chosen in order to prove structural changes due to exhaust

dyeing.

Weighing

All fabric duplicates were weighted before and after dyeing on a calibrated scale

from Kern & Sohn GmbH of type ABJ 220-4M, with a resolution of 0.1 mg. Prior

to weighing the samples were conditioned for at least 24 hours in standardised

atmosphere for conditioning of textiles, the temperature in the standardised atmos-

phere is 20°C ± 2°C and the relative humidity is 65% ± 2%. The scale used was not

located in standardised atmosphere. An average weight before and after dyeing for

every sample was calculated and based on the average values the weight difference

in percentage was calculated.

Vacuum drying and weighing

Vacuum drying was carried out in a vacuum cabinet Vacucell 22 from MMM

Medcenter Einrichtungen GmbH. The fabric duplicates were dried in 50°C for 17

hours. Two fabric duplicates from each sample was weighed before and after vacu-

um drying and an average percentage weight difference was calculated. The fabric

duplicates were weighed by a calibrated scale from Kern & Sohn GmbH of type

ALS 120-4, with a resolution of 0.1 mg. The fabric duplicates were kept in a desic-

cator between vacuum drying and weighing.

Tensile test

Tensile tests were performed on filament warp yarns from dissembled fabric sam-

ples on Mesdan electromechanical tensile tester. The instrument was equipped with

pneumatic grips and a 0.1 kN load cell.

Five warp yarns from each fabric duplicate were tested, meaning tensile testing of

20 yarns per sample. The test parameters used in the Tensolab software are shown

in Table 8. No preload was used. Before tensile testing the fabric duplicates were

conditioned for at least 24 hours in standardised atmosphere for conditioning of

textiles. The tests were performed in standardised atmosphere for testing of tex-

tiles.

29

TABLE 8 TENSILE TEST PARAMETERS USED IN TENSOLAB SOFTWARE

Test parameter Value

Method Yarn traction

Sample length 50.0 mm

Yarn count 16.7 tex for PETC

11.0 tex for PETM

Test speed 50.0 mm/min

Recording rate 0.1 mm

Average values on breaking strength and elongation at break was obtained through

the Tensolab software. Young’s modulus was calculated from the raw data based

on the initial, steepest part of the stress-strain curves.

Demand absorbency test

To investigate potential changes in hydrophilicity demand absorbency tests were

carried out according to ISO 9073-12:2002. Demand Absorbency Capacity (DAC)

and Maximum Absorption Rate (MAR) was investigated. DAC is the maximum

absorbed mass of liquid divided by the mass of the test specimen. DAC is ex-

pressed in g/g. MAR is the maximum change in liquid absorbed mass per time

interval. MAR is expressed in g/s. (European Committee for Standardization 2004)

Four fabric duplicates for each sample and four reference duplicates for PETC and

PETM were tested. The fabric duplicates were conditioned for at least 24 hours in

standardised atmosphere for conditioning of textiles before testing. The tests were

performed in standardised atmosphere for testing of textiles. Deionised water was

used for the tests.

Fourier-Transform Infrared spectroscopy

FTIR was performed using Nicolet iS10 with diamond SMART iTX from Thermo

Scientific. The software Omnic (Thermo Scientific) was used for data collection.

Four fabric duplicates for each sample and four reference duplicates were charac-

terised. An average of 64 readings per duplicate was noted and based on that an

average spectrum for each sample was constructed. Before analysis the spectra

were normalised to the maximum peak at the band around 1410 cm-1

using Excel

(Microsoft). This band has been used for normalisation in the literature investigat-

ing degradation and modification PET (e.g. Donelli et al. 2010; Badia et al. 2012).

Differential Scanning Calorimetry

DSC was performed using DSC Q1000 from TA Instruments. One fabric duplicate

for each sample and one reference from each weave (PETC and PETM) were char-

acterised. The sample sizes used was between 3.5 mg and 4.5 mg. Two heating

cycles and one cooling cycle were performed in a nitrogen atmosphere, in the tem-

perature range 25 – 300°C. Ramping rate was set to 20°C/min.

The software used for analysis of the data was TA Universal Analysis (TA Instru-

ments). Temperature intervals were decided, and within these intervals the peak

areas representing heat of melting (∆Hm) and heat of crystallisation (∆Hc) were

defined. The temperature intervals that were used are presented in Table 9.

30

TABLE 9 TEMPERATURE INTERVALS USED FOR DSC DATA ANALYSIS

Heat Temperature interval

1st heat of melting (∆Hm1), PETC 215 - 265°C

Heat of crystallisation (∆Hc), PETC 140 - 215°C

2nd

heat of melting (∆Hm2), PETC 215 - 265°C

1st heat of melting (∆Hm1), PETM 215 – 265°C

Heat of crystallisation (∆Hc), PETM 150 – 220°C

2nd

heat of melting (∆Hm2), PETM 215 – 265°C

Dissolving of PET fabrics

Trials on dissolving the PET fabrics were carried out using three different solvents,

with the aim to perform Size Exclusion Chromatography (SEC). Tetrahydrofuran

(THF), dimethyl sulfoxide (DMSO), and chloroform was used, based on what

could be used in the SEC column. A device for recirculation boiling (as shown in

Figure 9) was used for all trials.

FIGURE 9 RECIRCULATION BOILING DEVICE USED FOR TRIALS ON DISSOLVING OF PET

FABRICS.

A trial on dissolving a PETM fabric test specimen was performed using 30.3 mg of

fabric and 30.3 g of chloroform. Solvent and fabric was placed in the round bottom

flask (see Figure 9) and boiled for around 15 minutes.

A first trial of dissolving a PETC fabric test specimen was performed using DMSO

and lithium bromide. 14.5 mg of lithium bromide was added to 16.67 g of DMSO

to create a 0.1 molar concentration. Solvent and 50 mg of fabric was placed in the

round bottom flask and boiled for around 15 minutes. A second trial using 16.67 g

31

of THF and 50 mg of PETC fabric test specimen was performed. Solvent and fab-

ric was placed in the round bottom flask and boiled for around 15 minutes.

3.3. STATISTICAL ANALYSES Analysis of variance (ANOVA) and Tukey tests were performed to investigate

significant differences between the means of the samples. All dyed samples and the

reference samples for PETC and PETM were compared by ANOVA and Tukey tests

respectively. A confidence level of 95% was used for ANOVA. For Tukey tests an

error rate for comparisons of 5 was used. Statistical tests were performed using

Minitab 17 Statistical Software (Minitab).

Pearson correlation coefficients (linear correlation) were established using Minitab

17 Statistical Software. For correlation analysis a significance level of 95% was

applied. This means that if the p-value for the correlation coefficient is equal to or

smaller than 0.05 the correlation is statistically significant (Minitab Express 2016).

3.4. DATA MODIFICATION FOR GRAPH CONSTRUCTION Before presentation of the obtained data in form of graphs certain modifications

were performed. The data was exaggerated with a certain value depending on the

property presented, in order to separate the graphs for each bath composition. This

was done in order to construct multiple graphs within one figure in order for com-

parison to be possible. The values that have been exaggerated and how (addition or

subtraction) the values have been exaggerated is described in the figure texts.

32

4. RESULTS The results obtained from the characterisation of the samples are presented in the

upcoming sections.

4.1. WEIGHT DIFFERENCES First, percentage weight differences due to dyeing are presented. Second, percent-

age weight differences in dyed samples due to vacuum drying are presented.

4.1.1. WEIGHT DIFFERENCES DUE TO DYEING

The weight differences observed have been plotted against the exposure time above

Tg. The values presented in the graphs below are averages of four fabric duplicates

per sample. The percentage weight differences for the PETC samples due to dyeing

are shown in the graphs in Figure 10 and Figure 11. Figure 10 shows the weight

differences for the samples that have been exposed to one dyeing cycle, and the

three different bath compositions. Figure 10 shows the weight differences for the

samples that have been exposed to one, three, and five dyeing cycles in the bath

containing all auxiliary chemicals.

FIGURE 10 AVERAGE WEIGHT DIFFERENCE OBSERVED IN PETC SAMPLES EXPOSED TO ONE

DYEING CYCLE. FOR CLARITY, AVERAGE WEIGHT DIFFERENCE FOR BATH L AND BATH D

HAS BEEN EXAGGERATED BY 0.5% AND 1% RESPECTIVELY.

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 50 100 150 200 250

Aver

ag

e w

eig

ht

dif

fere

nce

[%

]

Exposure time above Tg [min]

105°C

120°C

135°C

105°C

120°C

135°C

105°C

120°C

135°C

Bath d

Bath l

Bath p

33

FIGURE 11 AVERAGE WEIGHT DIFFERENCE OBSERVED IN PETC SAMPLES EXPOSED TO

ONE, THREE OR FIVE DYEING CYCLES IN BATH D. FOR CLARITY, AVERAGE WEIGHT DIF-

FERENCE FOR 135°C, 30 MIN AND 135°C, 60 MIN HAS BEEN EXAGGERATED BY 1%.

The percentage weight differences for the PETM samples due to dyeing are shown

in the graphs in Figure 12 and Figure 13. Figure 12 shows the weight differences

for the samples that have been exposed to one dyeing cycle, and the three different

bath compositions. Figure 13 shows the weight differences for the samples that

have been exposed to one, three, and five dyeing cycles and bath containing all

auxiliary chemicals.

FIGURE 12 AVERAGE WEIGHT DIFFERENCE OBSERVED IN PETM SAMPLES EXPOSED TO ONE

DYEING CYCLE. FOR CLARITY, AVERAGE WEIGHT DIFFERENCE FOR BATH L AND BATH D

HAS BEEN EXAGGERATED BY 0.5% AND 1% RESPECTIVELY.

0

0.5

1

1.5

2

2.5

3

0 100 200 300 400 500 600

Aver

ag

e w

eig

ht

dif

fere

nce

[%

]


105°C, 30 min

105°C, 60 min

135°C, 30 min

135°C, 60 min

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 50 100 150 200 250

Aver

ag

e w

eig

ht

dif

fere

nce

[%

]


105°C

120°C

135°C

105°C

120°C

135°C

105°C

120°C

135°C

Bath d

Bath l

Bath p

34

FIGURE 13 AVERAGE WEIGHT DIFFERENCE OBSERVED IN PETM SAMPLES EXPOSED TO

ONE, THREE OR FIVE DYEING CYCLES IN BATH D. FOR CLARITY, AVERAGE WEIGHT DIF-

FERENCE FOR 135°C, 30 MIN AND 135°C, 60 MIN HAS BEEN EXAGGERATED BY 1%.

The figures above show that the weight difference depends on the exposure time

above Tg (Figure 11 and Figure 13). Since new bath was added for every dyeing

cycle it seems that the concentration of chemicals that the fabric duplicates have

been exposed to is also a contributing factor. The average weight differences ob-

served in PETC and PETM are quite similar.

4.1.2. VACUUM DRYING

The average weight differences before and after vacuum drying are presented in

the figures below. The values presented are averages of the percentage weight dif-

ference for two fabric duplicates for each sample. Figure 14 to Figure 17 show the

result for PETC samples. Figure 18 to Figure 21 show the result for PETM samples.

As can be seen in the figures below, all PETC samples exhibited a decrease in

weight due to vacuum drying. This was not observed in PETM samples.

FIGURE 14 AVERAGE PERCENTAGE WEIGHT DIFFERENCE AFTER VACUUM DRYING OB-

SERVED IN PETC SAMPLES EXPOSED TO ONE DYEING CYCLES IN BATH P.

0

0.5

1

1.5

2

2.5

3

0 100 200 300 400 500 600

Aver

ag

e w

eig

ht

dif

fere

nce

[%

]


105°C, 30 min

105°C, 60 min

135°C, 30 min

135°C, 60 min

-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0

0 50 100 150 200 250

Aver

ag

e w

eig

ht

dif

fere

nce

[%

]


105°C

120°C

135°C

Bath p

35


SERVED IN PETC SAMPLES EXPOSED TO ONE DYEING CYCLES IN BATH L.


SERVED IN PETC SAMPLES EXPOSED TO ONE DYEING CYCLES IN BATH D.


SERVED IN PETC SAMPLES EXPOSED TO ONE, THREE AND FIVE DYEING CYCLES IN BATH D.

-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0

0 50 100 150 200 250

Aver

ag

e w

eig

ht

dif

fere

nce

[%

]


105°C

120°C

135°C

Bath l

-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0

0 50 100 150 200 250

Aver

ag

e w

eig

ht

dif

fere

nce

[%

]


105°C

120°C

135°C

Bath d

-0.35

-0.3

-0.25

-0.2

-0.15

-0.1

-0.05

0

0 100 200 300 400 500 600

Aver

ag

e w

eig

ht

dif

fere

nce

[%

]


105°C, 30 min

105°C, 60 min

135°C, 30 min

135°C, 60 min

36


SERVED IN PETM SAMPLES EXPOSED TO ONE DYEING CYCLES IN BATH P.


SERVED IN PETM SAMPLES EXPOSED TO ONE DYEING CYCLES IN BATH L.


SERVED IN PETM SAMPLES EXPOSED TO ONE DYEING CYCLES IN BATH D.

-0.25

-0.15

-0.05

0.05

0.15

0.25

0.35

0 50 100 150 200 250

Aver

ag

e w

eig

ht

dif

fere

nce

[%

]


105°C

120°C

135°C

Bath p

-0.25

-0.15

-0.05

0.05

0.15

0.25

0.35

0 50 100 150 200 250

Aver

ag

e w

eig

ht

dif

fere

nce

[%

]


105°C

120°C

135°C

Bath l

-0.25

-0.15

-0.05

0.05

0.15

0.25

0.35

0 50 100 150 200 250

Aver

ag

e w

eig

ht

dif

fere

nce

[%

]


105°C

120°C

135°C

Bath d

37


SERVED IN PETM SAMPLES EXPOSED TO ONE, THREE AND FIVE DYEING CYCLES IN BATH D.

4.2. TENSILE PROPERTIES The tensile properties presented are averages of 20 yarn tests for each sample.

Breaking strength, elongation at break, and Young’s modulus have been investi-

gated and statistically analysed.

4.2.1. BREAKING STRENGTH

Average breaking strengths for the PETC samples are shown in the graphs in Figure

22 and Figure 23. Figure 24 and Figure 25 show average breaking strengths for

PETM samples. The values presented in the graphs below are averages of four fab-

ric duplicates per sample. Figure 22 and 24 shows the average breaking strength

for samples that have been exposed to one dyeing cycle, in the three different

baths. Figure 23 and 25 shows the average breaking strength for the samples that

have been exposed to one, three and five dyeing cycles, in bath containing all aux-

iliary chemicals.

Statistical analysis showed that the samples with significantly different breaking

strength from PETC Ref exhibit a decreased breaking strength. This is the case for

both PETC and PETM samples. In Table 10 the PETC samples with significantly

different breaking strength are presented. The breaking strength of the PETC Ref

was 6.67 N. The complete Tukey test is presented in Appendix I. In Table 11 the

PETM samples with significantly different breaking strength are presented. The

breaking strength of the PETM Ref was 4.85 N. The complete Tukey test is pre-

sented in Appendix II. Significant results are also marked in the figures below.

As can be seen in Figure 23 there seem to be a decreasing trend in breaking

strength for the PETC samples exposed to 135°C for 60 min as the exposure time

above Tg increases. This seems to be the case also for PETM samples exposed to

the same dyeing conditions, as seen in Figure 25.

-0.35

-0.25

-0.15

-0.05

0.05

0.15

0.25

0.35

0 100 200 300 400 500 600

Aver

ag

e w

eig

ht

dif

fere

nce

[%

]


105°C, 30 min

105°C, 60 min

135°C, 30 min

105°C, 60 min

38

TABLE 10 PETC SAMPLES WITH BREAKING STRENGTH SIGNIFICANTLY DIFFERENT FROM

PETC REF.

Sample Average breaking

strength [N]

Temp. [°C] Exposure time above

Tg [min]

PETCT3d30×5 6.17 135 550

PETCT2p60 6.11 120 97.5

PETCT2d60 5.34 120 97.5

PETCT2l60 5.15 120 97.5

FIGURE 22 AVERAGE BREAKING STRENGTH OBSERVED IN PETC SAMPLES EXPOSED TO ONE

DYEING CYCLE. FOR CLARITY , AVERAGE BREAKING STRENGTH FOR BATH L AND BATH D

HAS BEEN EXAGGERATED BY 2 N AND 4 N RESPECTIVELY. VALUES SIGNIFICANTLY DIF-

FERENT FROM THE REFERENCE ARE MARKED WITH *.

FIGURE 23 AVERAGE BREAKING STRENGTH OBSERVED IN PETC SAMPLES EXPOSED TO

ONE, THREE AND FIVE DYEING CYCLES IN BATH D. FOR CLARITY, AVERAGE BREAKING

STRENGTH FOR 135°C, 30 MIN AND 135°C, 60 MIN HAS BEEN EXAGGERATED BY 2 N. VAL-

UES SIGNIFICANTLY DIFFERENT FROM THE REFERENCE ARE MARKED WITH *.

*

*

*

5

6

7

8

9

10

11

0 50 100 150 200 250

Aver

ag

e b

reak

ing

str

eng

th [

N]


105°C

120°C

135°C

105°C

120°C

135°C

105°C

120°C

135°C

Bath d

Bath l

Bath p

*

5

6

7

8

9

10

0 100 200 300 400 500 600

Aver

ag

e b

reak

ing

str

eng

th [

N]


105°C, 30 min

105°C, 60 min

135°C, 30 min

135°C, 60 min

39

TABLE 11 PETM SAMPLES WITH BREAKING STRENGTH SIGNIFICANTLY DIFFERENT FROM

PETM REF.

Sample Average breaking

strength [N]

Temp. [°C] Exposure time above

Tg [min]

PETMT3l60 4.61 135 110

PETMT3d30×5 4.58 135 400

PETMT2p60 4.57 120 97.5

PETMT3p180 4.56 135 230

PETMT3d60×3 4.55 135 330

PETMT3d180 4.49 135 230

PETMT3l180 4.44 135 230

PETMT3d60×5 4.41 135 550

FIGURE 24 AVERAGE BREAKING STRENGTH OBSERVED IN PETM SAMPLES EXPOSED TO

ONE DYEING CYCLE. FOR CLARITY, AVERAGE BREAKING STRENGTH FOR BATH L AND BATH

D HAS BEEN EXAGGERATED BY 2 N AND 4 N RESPECTIVELY. VALUES SIGNIFICANTLY DIF-

FERENT FROM THE REFERENCE ARE MARKED WITH *.

FIGURE 25 AVERAGE BREAKING STRENGTH OBSERVED IN PETM SAMPLES EXPOSED TO

ONE, THREE AND FIVE DYEING CYCLES IN BATH D. FOR CLARITY, AVERAGE BREAKING

STRENGTH FOR 135°C, 30 MIN AND 135°C, 60 MIN HAS BEEN EXAGGERATED BY 2 N. VAL-

UES SIGNIFICANTLY DIFFERENT FROM THE REFERENCE ARE MARKED WITH *.

*

* *

* * 4

5

6

7

8

9

10

0 50 100 150 200 250

Aver

ag

e b

reak

ing

str

eng

th [

N]


105°C

120°C

135°C

105°C

120°C

135°C

105°C

120°C

135°C

Bath d

Bath l

Bath p

* * *

3

4

5

6

7

8

0 100 200 300 400 500 600

Aver

ag

e b

reak

ing

str

eng

th [

N]


105°C, 30 min

105°C, 60 min

135°C, 30 min

135°C, 60 min

40

4.2.2. ELONGATION AT BREAK

In Table 12 the PETC samples with significantly different elongation at break com-

pared to PETC Ref are presented. The significantly different samples exhibit a de-

crease in elongation at break. The elongation at break of the PETC Reference sam-

ple was 19.27 mm. The complete Tukey test is presented in Appendix III. The re-

sult for PETC is also presented in Figure 26 and Figure 27.

In Table 13 the PETM sample with significantly different elongation at break com-

pared to PETM Ref is presented. The significantly different sample exhibits an in-

crease in elongation at break. The elongation at break of the PETM Ref was 24.7

mm. The complete Tukey test is presented in Appendix IV. The result for PETM is

also presented in Figure 28 and Figure 29.

TABLE 12 PETC SAMPLES WITH ELONGATION AT BREAK SIGNIFICANTLY DIFFERENT FROM

PETC REF.

Sample Average elongation at

break [mm]

Temp.

[°C]

Exposure time

above Tg [min]

PETCT1d30×3 17.8 105 165

PETCT1d60×3 17.8 105 425

PETCT1d30×5 17.7 105 275

PETCT2d60 17.6 120 97.5

PETCT3l60 17.0 120 97.5

FIGURE 26 AVERAGE ELONGATION AT BREAK OBSERVED IN PETC SAMPLES EXPOSED TO

ONE DYEING CYCLE. FOR CLARITY, AVERAGE ELONGATION AT BREAK FOR BATH 2 AND

BATH 3 HAS BEEN EXAGGERATED BY 5 MM AND 10 MM, RESPECTIVELY. VALUES SIGNIFI-

CANTLY DIFFERENT FROM THE REFERENCE ARE MARKED WITH *.

*

*

16

18

20

22

24

26

28

30

32

0 50 100 150 200 250

Aver

ag

e el

on

gati

on

at

bre

ak

[m

m]

Time above Tg [min]

105°C

120°C

135°C

105°C

120°C

135°C

105°C

120°C

135°C

Bath 3

Bath 2

Bath 1

41

FIGURE 27 AVERAGE ELONGATION AT BREAK OBSERVED IN PETC SAMPLES EXPOSED TO

ONE, THREE AND FIVE DYEING CYCLES. FOR CLARITY, AVERAGE ELONGATION AT BREAK

FOR 135°C, 30 MIN AND 135°C, 60 MIN HAS BEEN EXAGGERATED BY 5 MM. VALUES SIGNIF-

ICANTLY DIFFERENT FROM THE REFERENCE ARE MARKED WITH *.

TABLE 13 PETM SAMPLES WITH ELONGATION AT BREAK SIGNIFICANTLY DIFFERENT FROM

PETM REF.

Sample Average elongation at

break [mm]

Temp.

[°C]

Exposure time

above Tg [min]

PETCT3p30 26.5 135 80

FIGURE 28 AVERAGE ELONGATION AT BREAK OBSERVED IN PETM SAMPLES EXPOSED TO

ONE DYEING CYCLE. FOR CLARITY, AVERAGE ELONGATION AT BREAK FOR BATH L AND

BATH D HAS BEEN EXAGGERATED BY 5 MM AND 10 MM, RESPECTIVELY. VALUES SIGNIFI-

CANTLY DIFFERENT FROM THE REFERENCE ARE MARKED WITH *.

* * *

16

18

20

22

24

26

0 100 200 300 400 500 600

Aver

ag

e el

on

gati

on

at

bre

ak

[m

m]

Time above Tg [min]

105°C, 30 min

105°C, 60 min

135°C, 30 min

135°C, 60 min

*

22

24

26

28

30

32

34

36

38

0 50 100 150 200 250

Aver

ag

e el

on

gati

on

at

bre

ak

[m

m]


105°C

120°C

135°C

105°C

120°C

135°C

105°C

120°C

135°C

Bath d

Bath l

Bath p

42

FIGURE 29 AVERAGE ELONGATION AT BREAK OBSERVED IN PETM SAMPLES EXPOSED TO

ONE, THREE AND FIVE DYEING CYCLES IN BATH D. FOR CLARITY, AVERAGE ELONGATION

AT BREAK FOR 135°C, 30 MIN AND 135°C, 60 MIN HAS BEEN EXAGGERATED BY 5 MM. NO

VALUES WERE FOUND TO BE STATISTICALLY DIFFERENT FROM PETM REF.

4.2.3. YOUNG’S MODULUS

Statistical analysis showed that 16 of the PETC samples have a Young’s modulus

significantly different from PETC Ref, these samples are presented in Table 14.

The Young’s moduli for these samples are larger than the modulus for the refer-

ence sample. The complete Tukey test is presented in Appendix V. The average

Young’s modulus of the PETC Ref was 0.0301 N/tex. The result is also shown in

graphs in Figure 30 and Figure 31.

Statistical analysis showed that three of the PETM samples have Young’s modulus

significantly different from PETM Ref, these samples are presented in Table 15.

Two samples have significantly larger moduli than PETM Ref and one sample have

a modulus significantly smaller than the reference. The complete Tukey test is

presented in Appendix VI. The average Young’s modulus of the PETM Ref was

0.0534 N/tex. The result is also shown in graphs in Figure 32 and Figure 33.

22

24

26

28

30

32

0 100 200 300 400 500 600Aver

ag

e el

on

gati

on

at

bre

ak

[m

m]


105°C, 30 min

105°C, 60 min

135°C, 30 min

135°C, 60 min

43

TABLE 14 PETC SAMPLES WITH A YOUNG’S MODULUS SIGNIFICANTLY DIFFERENT FROM

PETC REF.

Sample Average Young’s

modulus [N/tex]

Temperature

[°C]

Exposure time

above Tg [min]

PETCT2p30 0.0504 120 67.5

PETCT1l60 0.0498 105 85

PETCT1l30 0.0494 105 55

PETCT1p180 0.0479 105 205

PETCT1l180 0.0478 105 205

PETCT3p180 0.0469 135 230

PETCT1d30 0.0468 105 55

PETCT3d180 0.0446 135 230

PETCT3p60 0.0427 135 110

PETCT3d30×3 0.0425 135 240

PETCT3d60×5 0.0413 135 550

PETCT2d60 0.0399 120 97.5

PETCT1d30×3 0.0395 105 165

PETCT1d60 0.0394 105 85

PETCT2p60 0.0392 120 97.5

PETCT1d60×3 0.0391 105 255

FIGURE 30 AVERAGE YOUNG'S MODULUS OBSERVED IN PETC SAMPLES EXPOSED TO ONE

DYEING CYCLE. FOR CLARITY, AVERAGE YOUNG’S MODULUS FOR BATH L AND BATH D HAS

BEEN EXAGGERATED BY 0.1 N/TEX AND 0.2 N/TEX RESPECTIVELY. VALUES SIGNIFICANTLY

DIFFERENT FROM THE REFERENCE ARE MARKED WITH *.

* * * *

* * *

* * * * *

0

0.05

0.1

0.15

0.2

0.25

0.3

0 50 100 150 200 250

Aver

ag

e Y

ou

ng

's m

od

ulu

s [N

/tex

]

Time above Tg [min]

105°C

120°C

135°C

105°C

120°C

135°C

105°C

120°C

135°C

Bath d

Bath l

Bath p

44

FIGURE 31 AVERAGE YOUNG'S MODULUS OBSERVED IN PETC SAMPLES EXPOSED TO ONE,

THREE OR FIVE DYEING CYCLES IN BATH D. FOR CLARITY, AVERAGE YOUNG'S MODULUS

FOR 135°C, 30 MIN AND 135°C, 60 MIN HAS BEEN EXAGGERATED BY 0.1 N/TEX. VALUES

SIGNIFICANTLY DIFFERENT FROM THE REFERENCE ARE MARKED WITH *.

TABLE 15 PETM SAMPLES WITH A YOUNG’S MODULUS SIGNIFICANTLY DIFFERENT FROM

PETM REF.

Sample Average Young’s

modulus [N/tex]

Temperature

[°C]

Exposure time

above Tg [min]

PETMT3l180 0.0331 135 230

PETMT1d60 0.0692 105 85

PETMT2p180 0.0698 120 217.5

FIGURE 32 AVERAGE YOUNG'S MODULUS OBSERVED IN PETM SAMPLES EXPOSED TO ONE

DYEING CYCLE. FOR CLARITY, AVERAGE YOUNG’S MODULUS FOR BATH D AND BATH L HAS

BEEN EXAGGERATED BY 0.1 N/TEX AND 0.2 N/TEX RESPECTIVELY. VALUES SIGNIFICANTLY

DIFFERENT FROM THE REFERENCE ARE MARKED WITH *.

* * * *

* *

0.00

0.05

0.10

0.15

0.20

0 100 200 300 400 500 600

Aver

ag

e Y

ou

ng

's m

od

ulu

s [N

/tex

]

Time above Tg [min]

105°C, 30 min

105°C, 60 min

135°C, 30 min

135°C, 60 min

*

*

*

0

0.05

0.1

0.15

0.2

0.25

0.3

0 50 100 150 200 250

Aver

ag

e Y

ou

ng

's m

od

ulu

s [N

/tex

]


105°C

120°C

135°C

105°C

120°C

135°C

105°C

120°C

135°C

Bath d

Bath l

Bath p

45

FIGURE 33 AVERAGE YOUNG'S MODULUS OBSERVED IN PETM SAMPLES EXPOSED TO ONE,

THREE OR FIVE DYEING CYCLES IN BATH D. FOR CLARITY, AVERAGE YOUNG'S MODULUS

FOR 135°C, 30 MIN AND 135°C, 60 MIN HAS BEEN EXAGGERATED BY 0.1 N/TEX. NO VALUES

WERE FOUND TO BE STATISTICALLY DIFFERENT FROM PETM REF.

4.3. DEMAND ABSORBENCY CAPACITY AND MOISTURE ABSORPTION

RATE The result of the demand absorbency test is presented in Table 16 and Table 17.

The values presented in the tables are average values of tests of four fabric dupli-

cates. Statistical analysis showed that two PETC sample exhibit a significantly dif-

ferent DAC compared to PETC Ref. The PETC samples exhibit a higher average

DAC than PETC Ref. Three samples exhibit a statistically significant MAR, com-

pared to PETC Ref, these samples have a higher MAR. The complete Tukey test for

DAC for PETC samples is presented in Appendix VII and the Tukey test for MAR

for PETC is presented in Appendix VIII. As can be seen in Table 16 the lowest

DAC for PETC is observed in PETC Ref.

The statistical analysis showed that all PETM samples exhibit an average DAC

significantly different from the PETM Ref. Dyeing of the PETM samples have re-

sulted in lower DAC compared to PETM Ref. Two samples exhibit a statistically

significant MAR, compared to PETM Ref, these samples have a higher MAR. The

complete Tukey test for DAC for PETM samples is presented in Appendix IX and

the Tukey test for MAR for PETM is presented in Appendix X. As can be seen in

Table 17 most of the dyed PETM samples exhibit a MAR lower than PETM Ref.

0

0.05

0.1

0.15

0.2

0 100 200 300 400 500 600

Aver

ag

e el

on

gati

on

at

bre

ak

[m

m]


105°C, 30 min

105°C, 60 min

135°C, 30 min

135°C, 60 min

46

TABLE 16 AVERAGE DEMAND ABSORBENCY CAPACITY AND AVERAGE MOISTURE ABSORP-

TION RATE OBSERVED IN PETC SAMPLES. SAMPLES WITH SIGNIFICANTLY DIFFERENT VAL-

UES COMPARED TO THE REFERENCE SAMPLES ARE MARKED WITH *.

Sample Average DAC [g/g] Average MAR [g/s]

PETCRef 1.08 0.16

PETCT1p30 1.30 0.11

PETCT1l30 1.31 0.23

PETCT1d30 1.16 0.22

PETCT1d30×3 1.19 0.22

PETCT1d30×5 1.21 0.22

PETCT1p60 1.25 0.13

PETCT1l60 1.23 0.26*

PETCT1d60 1.40 0.22

PETCT1d60×3 1.30 0.22

PETCT1d60×5 1.22 0.20

PETCT1p180 1.41 0.16

PETCT1l180 1.19 0.22

PETCT1d180 1.20 0.21

PETCT2p30 1.41 0.18

PETCT2l30 1.43 0.22

PETCT2d30 1.30 0.23

PETCT2p60 1.43 0.20

PETCT2l60 1.45 0.29*

PETCT2d60 1.80* 0.22

PETCT2p180 1.47 0.19

PETCT2l180 1.23 0.22

PETCT2d180 1.40 0.22

PETCT3p30 1.33 0.17

PETCT3l30 1.39 0.22

PETCT3d30 1.30 0.22

PETCT3d30×3 1.41 0.27*

PETCT3d30×5 1.48 0.23

PETCT3p60 1.20 0.19

PETCT3l60 1.38 0.23

PETCT3d60 1.29 0.21

PETCT3d60×3 1.25 0.22

PETCT3d60×5 1.31 0.22

PETCT3p180 1.34 0.17

PETCT3l180 1.40 0.21

PETCT3d180 1.65* 0.20

47

TABLE 17 AVERAGE DEMAND ABSORBENCY CAPACITY AND AVERAGE MOISTURE ABSORP-

TION RATE OBSERVED IN PETM SAMPLES. SAMPLES WITH SIGNIFICANTLY DIFFERENT

VALUES COMPARED TO THE REFERENCE SAMPLES ARE MARKED WITH *.

Sample Average DAC [g/g] Average MAR [g/s]

PETMRef 1.92 0.32

PETMT1p30 1.33* 0.21

PETMT1l30 1.18* 0.62*

PETMT1d30 1.30* 0.22

PETMT1d30×3 1.29* 0.22

PETMT1d30×5 1.25* 0.21

PETMT1p60 1.08* 0.18

PETMT1l60 0.95* 0.17

PETMT1d60 1.03* 0.19

PETMT1d60×3 1.22* 0.20

PETMT1d60×5 1.18* 0.18

PETMT1p180 1.33* 0.20

PETMT1l180 1.25* 0.54*

PETMT1d180 1.13* 0.48

PETMT2p30 1.03* 0.16

PETMT2l30 1.07* 0.18

PETMT2d30 0.96* 0.18

PETMT2p60 1.07* 0.18

PETMT2l60 0.95* 0.18

PETMT2d60 0.98* 0.18

PETMT2p180 1.04* 0.17

PETMT2l180 0.91* 0.16

PETMT2d180 0.97* 0.17

PETMT3p30 1.02* 0.17

PETMT3l30 1.17* 0.20

PETMT3d30 1.09* 0.30

PETMT3d30×3 1.14* 0.19

PETMT3d30×5 1.19* 0.19

PETMT3p60 1.15* 0.17

PETMT3l60 1.04* 0.18

PETMT3d60 1.22* 0.19

PETMT3d60×3 1.14* 0.19

PETMT3d60×5 1.14* 0.18

PETMT3p180 1.14* 0.17

PETMT3l180 1.08* 0.18

PETMT3d180 1.11* 0.20

Table 16 and Table 17 show that DAC of the two different PET fabrics seem to be

affected in opposite manner by the dyeing processes. The thinner filaments (PETM)

exhibit decreased DAC while the thicker filaments (PETC) exhibit increased DAC.

This can also be seen in Figure 34 and Figure 35 (PETC) and in Figure 36 and Fig-

ure 37 (PETM). PETC and PETM samples exposed to multiple dyeing cycles exhibit

similar change in the MAR, which can be seen in Figure 37 and Figure 39.

48

FIGURE 34 AVERAGE DAC OBSERVED IN PETC SAMPLES EXPOSED TO ONE DYEING CYCLE.

FOR CLARITY, AVERAGE DAC FOR BATH L AND BATH D HAS BEEN EXAGGERATED BY 1 G/G

AND 2 G/G RESPECTIVELY. VALUES SIGNIFICANTLY DIFFERENT FROM PETC REF ARE

MARKED WITH *.

FIGURE 35 AVERAGE DAC OBSERVED IN PETC SAMPLES EXPOSED TO ONE, THREE AND

FIVE DYEING CYCLES IN BATH D. FOR CLARITY, AVERAGE DAC FOR 135°C, 30 MIN AND

135°C, 60 MIN HAS BEEN EXAGGERATED BY 1 G/G. NO VALUES WERE FOUND TO BE

SIGIFICANTLY DIFFERENT FROM PETC REF.

* *

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

0 50 100 150 200 250

Aver

ag

e D

eman

d A

bso

rben

cy C

ap

aci

ty

[g/g

]


105°C

120°C

135°C

105°C

120°C

135°C

105°C

120°C

135°C

Bath d

Bath l

Bath p

0

0.5

1

1.5

2

2.5

3

0 100 200 300 400 500 600

Aver

ag

e D

eman

d A

bso

rben

cy

Cap

aci

ty [

g/g

]


105°C, 30 min

105°C, 60 min

135°C, 30 min

135°C, 60 min

49

FIGURE 36 AVERAGE DAC OBSERVED IN PETM SAMPLES EXPOSED TO ONE DYEING CYCLE .

FOR CLARITY, AVERAGE DAC FOR BATH L AND BATH D HAS BEEN EXAGGERATED BY 1 G/G

AND 2 G/G RESPECTIVELY. ALL VALUES ARE SIGNIFICANTLY DIFFERENT FROM PETM REF

AND THEREFORE NOT MARKED IN THIS FIGURE.

FIGURE 37 AVERAGE DAC OBSERVED IN PETM SAMPLES EXPOSED TO ONE, THREE AND

FIVE DYEING CYCLES IN BATH D. FOR CLARITY, AVERAGE DAC FOR 135°C, 30 MIN AND

135°C, 60 MIN HAS BEEN EXAGGERATED BY 1 G/G. ALL VALUES ARE SIGNIFICANTLY DIF-

FERENT FROM PETM REF AND THEREFORE NOT MARKED IN THIS FIGURE.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0 50 100 150 200 250

Aver

ag

e D

eman

d A

bso

rben

cy C

ap

aci

ty [

g/g

]


105°C

120°C

135°C

105°C

120°C

135°C

105°C

120°C

135°C

Bath d

Bath l

Bath p

0

0.5

1

1.5

2

2.5

3

0 100 200 300 400 500 600

Aver

ag

e M

ax

imu

m A

bso

rpti

on

Rate

[g

/s]


105°C, 30 min

105°C, 60 min

135°C, 30 min

135°C, 60 min

50

FIGURE 38 AVERAGE MAR OBSERVED IN PETC SAMPLES EXPOSED TO ONE DYEING CY-

CLE. AVERAGE MAR FOR BATH L AND BATH D HAS BEEN EXAGGERATED BY 0.5 G/S AND 1

G/S RESPECTIVELY. VALUES SIGNIFICANTLY DIFFERENT FROM PETC REF ARE MARKED

WITH *.

FIGURE 39 AVERAGE MAR OBSERVED IN PETC SAMPLES EXPOSED TO ONE, THREE AND

FIVE DYEING CYCLES IN BATH D. FOR CLARITY, AVERAGE MAR FOR 135°C, 30 MIN AND

135°C, 60 MIN HAS BEEN EXAGGERATED BY 1 G/S. VALUES SIGNIFICANTLY DIFFERENT

FROM PETC REF ARE MARKED WITH *.

* *

0.00

0.25

0.50

0.75

1.00

1.25

1.50

0 50 100 150 200 250

Aver

ag

e M

ax

imu

m A

bso

rpti

on

Rate

[g

/s]


105°C

120°C

135°C

105°C

120°C

135°C

105°C

120°C

135°C

Bath d

Bath l

Bath p

*

0

0.25

0.5

0.75

1

0 100 200 300 400 500 600

Aver

ag

e M

ois

ture

Ab

sorp

tion

Rate

[g

/s]


105°C, 30 min

105°C, 60 min

135°C, 30 min

135°C, 60 min

51

FIGURE 40 AVERAGE MAR OBSERVED IN PETM SAMPLES EXPOSED TO ONE DYEING CY-

CLE. AVERAGE MAR FOR BATH 2 AND BATH 3 HAS BEEN EXAGGERATED BY 0.5 G/S AND 1

G/S RESPECTIVELY. VALUES SIGNIFICANTLY DIFFERENT FROM PETM REF ARE MARKED

WITH *.

FIGURE 41 AVERAGE MAR OBSERVED IN PETM SAMPLES EXPOSED TO ONE, THREE AND

FIVE DYEING CYCLES. FOR CLARITY, AVERAGE MAR FOR 135°C, 30 MIN AND 135°C, 60

MIN HAS BEEN EXAGGERATED BY 1 G/S. NO VALUES WERE FOUND TO BE SIGIFICANTLY

DIFFERENT FROM PETM REF.

4.4. FOURIER-TRANSFORM INFRARED SPECTROSCOPY The results of the FTIR are presented in form of spectra and absorbance ratios. All

spectra in full scale can be seen in Appendix XI (PETC) and Appendix XII (PETM).

The spectra in the figures below have been normalised at 1409 cm-1

. Also, the rati-

os are calculated from normalised spectra.

As can be seen in Figure 42 and Figure 43 changes in the spectral data in the range

of 1420 – 1620 cm-1

can be observed. These changes are observed after exposure to

three and five dyeing cycles in 105°C in bath composition 3. Around 1585 cm-1

a

new peak has emerged in PETCT1d30×5 and PETCT1d30×5. An intensity increase

* *

0

0.25

0.5

0.75

1

1.25

1.5

0 50 100 150 200 250

Aver

ag

e M

ax

imu

m A

bso

rpti

on

Rate

[g

/s]


105°C

120°C

135°C

105°C

120°C

135°C

105°C

120°C

135°C

Bath 3

Bath 2

Bath 1

0

0.25

0.5

0.75

1

1.25

1.5

0 100 200 300 400 500 600

Aver

ag

e M

ax

imu

m A

bso

rpti

on

Rate

[g

/s]


105°C, 30 min

105°C, 60 min

135°C, 30 min

135°C, 60 min

52

can be observed at 1578 cm-1

for samples exposed to three and five dyeing cycles

for both 30 and 60 minutes.

Around 1534 cm-1

emerging peaks can also be observed. The intensity increases

with increased number of dyeing cycles for the samples dyed in both 30 and 60

minutes. Intensity increase of the peaks at 1449 cm-1

can also be observed depend-

ent on the number of dyeing cycles. Intensity increase can also be observed at 1469

cm-1

.

FIGURE 42 MAGNIFIED FTIR SPECTRA FOR PETC SAMPLES EXPOSED TO DYEING IN 105°C

FOR 30 MINUTES.


FOR 60 MINUTES.

Similar changes in spectral data can be observed in PETM samples, as seen in Fig-

ure 44 to Figure 47. For PETM changes are observed also in samples dyed in

135°C. However, the spectral changes in the samples dyed in 135°C are not as

large as those observed in samples dyed in 105°C.

14

49

14

69

15

34

15

78

1

58

5

0

0.05

0.1

0.15

0.2

13001400150016001700A

bso

rban

ce

Wavenumber [cm-1]

PETC Ref

PETC T1 p 30

PETC T1 l 30

PETC T1 d 30

PETC T1 d 30×3

PETC T1 d 30×5

14

49

14

69

15

34

15

78

15

85

0

0.05

0.1

0.15

0.2

13001400150016001700

Ab

sorb

an

ce

Wavenumber [cm⁻¹]

PETC Ref

PETC T1 p 60

PETC T1 l 60

PETC T1 d 60

PETC T1 d 60×3

PETC T1 d 60×5

53

FIGURE 44 MAGNIFIED FTIR SPECTRA FOR PETM SAMPLES EXPOSED TO DYEING IN 105°C

FOR 30 MINUTES.


FOR 60 MINUTES.

14

49

14

69

15

34

15

78

15

85

0

0.05

0.1

0.15

0.2

13001400150016001700

Ab

sorb

an

ce

Wavenumber [cm-1]

PETM Ref

PETM T1 p 30

PETM T1 l 30

PETM T1 d 30

PETM T1 d 30×3

PETM T1 d 30×5

14

49

14

69

15

34

15

78

15

85

0

0.05

0.1

0.15

0.2

13001400150016001700

Ab

sorb

an

ce

Wavenumber [cm-1]

PETM Ref

PETM T1 p 60

PETM T1 l 60

PETM T1 d 60

PETM T1 d 60×3

PETM T1 d 60×5

54


FOR 30 MINUTES.


FOR 60 MINUTES.

14

49

14

69

15

38

15

78

0

0.05

0.1

0.15

0.2

13001400150016001700

Ab

sorb

an

ce

Wavenumber [cm-1]

PETM Ref

PETM T3 p 30

PETM T3 l 30

PETM T3 d 30

PETM T3 d 30×3

PETM T3 d 30×5

14

50

14

69

15

38

15

78

0

0.05

0.1

0.15

0.2

13001400150016001700

Ab

sorb

an

ce

Wavenumber [cm-1]

PETM Ref

PETM T3 p 60

PETM T3 l 60

PETM T3 d 60

PETM T3 d 60×3

PETM T3 d 60×5

55

As can be seen in Figure 48 there are obvious changes in the spectral data for

PETMT3d60×5.

FIGURE 48 MAGNIFIED FTIR SPECTRA FOR PETM SAMPLES EXPOSED TO DYEING AT

135°C FOR DYEING CYCLES OF 60 MIN

4.4.1. ABSORBANCE RATIOS

Absorbance ratios for peaks suggested to be included in trans-gauche couples are

presented in the tables below. Table 18 shows the ratios for PETC samples and

Table 19 shows the ratios for PETM samples.

The peak at 1371 cm-1

arises from CH2 wagging of the ethylene glycol in the

amorphous phase, representing the gauche conformation of the ethylene glycol.

The peak at 1339 cm-1

(PETC) or 1340 cm-1

(PETM) arises from CH2 wagging in

the crystalline phase, representing the trans conformation of the ethylene glycol.

Peaks at these wavenumbers have been suggested to form a trans-gauche couple.

The peaks at 847 cm-1

and 898 cm-1

are also suggested to form a trans-gauche cou-

ple, and are arises from CH2 rocking.

For the suggested trans-gauche couple 970 cm-1

and 1042 cm-1

, no peaks around

wavenumber 1042 cm-1

have been observed and therefore this couple is not inves-

tigated further.

28

49

29

17

0

0.025

0.05

0.075

0.1

275028502950305031503250

Ab

sorb

an

ce

Wavenumber [cm-1]

Reference

PETM T3 p 60

PETM T3 l 60

PETM T3 d 60

PETM T3 d 60×3

PETM T3 d 60×5

56

TABLE 18 ABSORBANCE RATIOS FOR ABSORBANCE PEAKS SUGGESTED TO FORM TRANS-

GAUCHE COUPLES CALCULATED FROM NORMALISED FTIR SPECTRA FOR PETC SAMPLES.

MAXIMUM VALUE IS MARKED WITH * AND MINIMUM VALUE IS MARKED WITH ^.

Sample A1371/A1409

Gauche

A1339/A1409

Trans

A898/A1409

Gauche

A847/A1409

Trans

PETCRef 0.397 1.064 0.870 1.297 PETCT1p30 0.417 1.064 0.880 1.304 PETCT1l30 0.412 1.058 0.864 1.292 PETCT1d30 0.414 1.074 0.913 1.334 PETCT1d30×3 0.453 1.059 0.877 1.312 PETCT1d30×5 0.490* 1.064 0.888 1.337 PETCT1p60 0.421 1.070 0.893 1.333 PETCT1l60 0.428 1.056 0.876 1.315 PETCT1d60 0.416 1.071 0.894 1.330 PETCT1d60×3 0.459 1.070 0.929 1.366 PETCT1d60×5 0.473 1.072 0.910 1.367* PETCT1p180 0.361^ 1.045 0.882 1.325 PETCT1l180 0.407 1.067 0.890 1.320 PETCT1d180 0.410 1.064 0.870 1.298 PETCT2p30 0.417 1.065 0.899 1.337 PETCT2l30 0.415 1.066 0.890 1.330 PETCT2d30 0.418 1.063 0.912 1.342 PETCT2p60 0.411 1.067 0.930* 1.356 PETCT2l60 0.424 1.077 0.924 1.355 PETCT2d60 0.424 1.072 0.917 1.342 PETCT2p180 0.409 1.073 0.913 1.335 PETCT2l180 0.414 1.068 0.913 1.336 PETCT2d180 0.418 1.081* 0.930* 1.342 PETCT3p30 0.387 1.015 0.866 1.267 PETCT3l30 0.394 1.021 0.862 1.266 PETCT3d30 0.386 0.988 0.836 1.228 PETCT3d30×3 0.407 0.987 0.848 1.241 PETCT3d30×5 0.405 0.935^ 0.825^ 1.198 PETCT3p60 0.387 1.002 0.870 1.272 PETCT3l60 0.385 0.987 0.848 1.254 PETCT3d60 0.380 0.980 0.868 1.261 PETCT3d60×3 0.403 0.962 0.868 1.254 PETCT3d60×5 0.414 0.939 0.848 1.223^ PETCT3p180 0.408 1.048 0.927 1.336 PETCT3l180 0.409 1.046 0.916 1.339 PETCT3d180 0.413 1.052 0.925 1.342

57

TABLE 19 ABSORBANCE RATIOS FOR ABSORBANCE PEAKS SUGGESTED TO FORM TRANS-

GAUCHE COUPLES CALCULATED FROM NORMALISED FTIR SPECTRA FOR PETM SAMPLES.


Sample A1371/A1409

Gauche

A1340/A1409

Trans

A898/A1409

Gauche

A847/A1409

Trans

PETMRef 0.4183 1.036 0.6348 1.075 PETMT1p30 0.3899 1.021 0.5940 1.061^ PETMT1l30 0.3832 1.025 0.5891^ 1.065 PETMT1d30 0.3817^ 1.020 0.5965 1.070 PETMT1d30×3 0.4151 1.021 0.5960 1.083 PETMT1d30×5 0.4616 1.012^ 0.6120 1.119 PETMT1p60 0.3859 1.020 0.6059 1.082 PETMT1l60 0.3845 1.019 0.5899 1.072 PETMT1d60 0.3892 1.013 0.6148 1.088 PETMT1d60×3 0.4115 1.019 0.6112 1.095 PETMT1d60×5 0.4544 1.021 0.6090 1.108 PETMT1p180 0.3863 1.024 0.5947 1.075 PETMT1l180 0.3865 1.019 0.5996 1.084 PETMT1d180 0.3845 1.022 0.5959 1.078 PETMT2p30 0.3874 1.019 0.6110 1.084 PETMT2l30 0.3838 1.024 0.5953 1.075 PETMT2d30 0.3821 1.020 0.5984 1.079 PETMT2p60 0.4271 1.038 0.6418 1.078 PETMT2l60 0.4289 1.029 0.6448 1.086 PETMT2d60 0.4307 1.035 0.6476 1.088 PETMT2p180 0.4271 1.034 0.6468 1.083 PETMT2l180 0.4271 1.036 0.6319 1.079 PETMT2d180 0.4272 1.036 0.6361 1.078 PETMT3p30 0.4241 1.038 0.6427 1.079 PETMT3l30 0.4241 1.035 0.6424 1.084 PETMT3d30 0.4281 1.038 0.6390 1.079 PETMT3d30×3 0.4485 1.048 0.6545 1.095 PETMT3d30×5 0.4691 1.051 0.6616 1.105 PETMT3p60 0.4246 1.042 0.6408 1.080 PETMT3l60 0.4242 1.043 0.6406 1.081 PETMT3d60 0.4279 1.036 0.6501 1.095 PETMT3d60×3 0.4456 1.054* 0.6473 1.087 PETMT3d60×5 0.4921* 1.046 0.6980* 1.127* PETMT3p180 0.4248 1.042 0.6377 1.080 PETMT3l180 0.4238 1.035 0.6450 1.092 PETMT3d180 0.4267 1.043 0.6483 1.088

58

Absorbance ratios for 1712 cm-1

(C=O stretching) for PETC and PETM are present-

ed in Table 20. Absorbance in this region has been studied in relation to degrada-

tion of PET. It is clear that the absorbance ratios for PETC samples have decreased

due to dyeing, meaning a decrease in absorbance intensity. The largest decrease

can be observed in PETCT3d60×5. For PETM the results are not as clear, but the

largest decrease can be observed in PETMT3d60×5.

TABLE 20 ABSORBANCE RATIOS FOR 1712 CM-1

CALCULATED FROM NORMALISED FTIR

SPECTRA FOR PETC AND PETM.

PETC PETM

Sample A1712/A1409

C=O stretching

Sample A1712/A1409

C=O stretching PETCRef 3.066* PETMRef 3.153 PETCT1p30 2.972 PETMT1p30 3.296 PETCT1l30 2.987 PETMT1l30 3.341 PETCT1d30 2.934 PETMT1d30 3.330 PETCT1d30×3 2.863 PETMT1d30×3 3.217 PETCT1d30×5 2.733 PETMT1d30×5 3.044 PETCT1p60 2.976 PETMT1p60 3.295 PETCT1l60 2.932 PETMT1l60 3.358* PETCT1d60 2.951 PETMT1d60 3.301 PETCT1d60×3 2.795 PETMT1d60×3 3.196 PETCT1d60×5 2.803 PETMT1d60×5 3.065 PETCT1p180 3.060 PETMT1p180 3.291 PETCT1l180 2.985 PETMT1l180 3.358* PETCT1d180 2.962 PETMT1d180 3.326 PETCT2p30 2.978 PETMT2p30 3.285 PETCT2l30 2.993 PETMT2l30 3.349 PETCT2d30 2.930 PETMT2d30 3.354 PETCT2p60 2.993 PETMT2p60 3.069 PETCT2l60 2.948 PETMT2l60 3.102 PETCT2d60 2.936 PETMT2d60 3.073 PETCT2p180 2.983 PETMT2p180 3.068 PETCT2l180 2.980 PETMT2l180 3.148 PETCT2d180 2.946 PETMT2d180 3.125 PETCT3p30 2.878 PETMT3p30 3.113 PETCT3l30 2.902 PETMT3l30 3.163 PETCT3d30 2.787 PETMT3d30 3.123 PETCT3d30×3 2.769 PETMT3d30×3 3.009 PETCT3d30×5 2.582 PETMT3d30×5 2.926 PETCT3p60 2.893 PETMT3p60 3.117 PETCT3l60 2.893 PETMT3l60 3.197 PETCT3d60 2.837 PETMT3d60 3.155 PETCT3d60×3 2.720 PETMT3d60×3 3.055 PETCT3d60×5 2.567^ PETMT3d60×5 2.879^ PETCT3p180 3.033 PETMT3p180 3.115 PETCT3l180 3.055 PETMT3l180 3.186 PETCT3d180 3.024 PETMT3d180 3.139

59

4.5. DIFFERENTIAL SCANNING CALORIMETRY The results of the DSC on PETC and PETM samples are presented in Table 21 and

Table 22, respectively. Heat of melting (∆Hm1), heat of crystallisation (∆Hc), and

second heat of melting (∆Hm2) are presented. Ratios between different heats are

presented in the tables. Also, the maximum temperature peaks for melting and

crystallisation are presented. ∆Hm1 is related to the degree of crystallinity according

to Equation 1. Higher heat of melting means higher degree of crystallinity.

TABLE 21 HEATS OF MELTING AND CRYSTALLISATION OBSERVED IN PETC SAMPLES.


Sample ∆Hm1

[J/g]

Peak

max.

Hm1

∆Hc

[J/g]

Peak

max.

Hc

∆Hm2

[J/g]

Peak

max.

Hm2

PETCRef 58 254 38 182 37 251 1.5 1.6 PETCT1p30 57 253 36 175 37 251 1.6 1.5 PETCT1l30 60 253 36 175 38 251 1.7 1.6 PETCT1d30 58 253 42 185 37 251 1.4 1.6 PETCT1d30×3 59 253 42 182 38 251 1.4 1.6 PETCT1d30×5 56 253 41 179 37 251 1.4 1.5 PETCT1p60 54 253 35^ 176 34^ 251 1.5 1.6 PETCT1l60 58 253 36 177 37 250 1.6 1.6 PETCT1d60 57 253 41 182 37 251 1.4 1.5 PETCT1d60×3 59 253 42 183 38 251 1.4 1.6 PETCT1d60×5 58 254 42 181 37 251 1.4 1.6 PETCT1p180 57 253 36 178 37 251 1.6 1.5 PETCT1l180 58 254 40 179 37 251 1.5 1.6 PETCT1d180 59 253 40 180 36 251 1.5 1.6 PETCT2p30 59 253 38 176 38 251 1.6 1.6 PETCT2l30 57 254 38 179 36 251 1.5 1.6 PETCT2d30 59 253 41 184 37 251 1.4 1.6 PETCT2p60 61 254 47 185 42 253 1.3 1.5 PETCT2l60 59 254 48* 189 43* 253 1.2 1.4 PETCT2d60 57 254 44 190 40 253 1.3 1.4 PETCT2p180 56 254 38 179 36 251 1.5 1.6 PETCT2l180 59 253 41 180 38 251 1.4 1.6 PETCT2d180 56 253 40 184 35 251 1.4 1.6 PETCT3p30 57 253 37 178 37 251 1.5 1.5 PETCT3l30 59 253 42 181 38 251 1.4 1.6 PETCT3d30 57 253 42 184 37 251 1.4 1.5 PETCT3d30×3 58 253 43 185 37 251 1.3 1.6 PETCT3d30×5 53^ 255 41 184 36 252 1.3 1.5 PETCT3p60 57 253 40 178 37 251 1.4 1.5 PETCT3l60 55 254 41 181 36 251 1.3 1.5 PETCT3d60 58 254 42 185 38 252 1.4 1.5 PETCT3d60×3 58 254 43 186 38 252 1.3 1.5 PETCT3d60×5 57 255 44 186 38 252 1.3 1.5 PETCT3p180 62* 254 45 184 41 252 1.4 1.5 PETCT3l180 58 253 41 182 38 252 1.4 1.5 PETCT3d180 59 253 42 185 38 252 1.4 1.6

60

TABLE 22 HEATS OF MELTING AND CRYSTALLISATION OBSERVED IN PETM SAMPLES.


Sample ∆Hm1

[J/g]

Peak

max.

Hm1

∆HC

[J/g]

Peak

max.

Hc

∆Hm2

[J/g]

Peak

max.

Hm2

PETMRef 60 253 42 191 38 251 1.4 1.6 PETMT1p30 55 254 36 180 36 251 1.5 1.5 PETMT1l30 55 254 35^ 184 35 251 1.6 1.6 PETMT1d30 59 254 42 186 38 251 1.4 1.6 PETMT1d30×3 57 253 37 181 35^ 250 1.5 1.6 PETMT1d30×5 59 253 42 185 38 251 1.4 1.6 PETMT1p60 58 253 39 182 37 250 1.5 1.6 PETMT1l60 59 254 36 179 37 250 1.6 1.6 PETMT1d60 59 253 39 183 37 251 1.5 1.6 PETMT1d60×3 56 253 39 183 36 250 1.4 1.6 PETMT1d60×5 61 253 43* 183 39* 251 1.4 1.6 PETMT1p180 58 253 37 181 37 250 1.6 1.6 PETMT1l180 59 253 36 180 37 251 1.6 1.6 PETMT1d180 59 253 40 182 37 250 1.5 1.6 PETMT2p30 62* 252 39 180 38 250 1.6 1.6 PETMT2l30 59 253 37 181 37 250 1.6 1.6 PETMT2d30 61 253 41 183 38 250 1.5 1.6 PETMT2p60 59 253 39 182 37 250 1.5 1.6 PETMT2l60 60 253 39 181 38 251 1.5 1.6 PETMT2d60 60 253 42 185 38 250 1.4 1.6 PETMT2p180 61 253 42 184 39* 251 1.5 1.6 PETMT2l180 58 253 39 183 37 251 1.5 1.6 PETMT2d180 58 253 40 184 37 251 1.5 1.6 PETMT3p30 60 253 41 184 38 250 1.5 1.6 PETMT3l30 59 253 37 181 37 251 1.6 1.6 PETMT3d30 60 253 42 186 37 250 1.4 1.6 PETMT3d30×3 56 253 40 186 36 251 1.4 1.6 PETMT3d30×5 56 253 41 185 37 251 1.4 1.5 PETMT3p60 60 253 41 183 38 251 1.5 1.6 PETMT3l60 58 254 39 182 37 251 1.5 1.6 PETMT3d60 58 253 40 184 38 251 1.5 1.5 PETMT3d60×3 57 253 42 186 37 251 1.4 1.5 PETMT3d60×5 54^ 253 40 186 36 252 1.4 1.5 PETMT3p180 58 254 43* 186 38 252 1.3 1.5 PETMT3l180 56 254 40 185 36 251 1.4 1.6 PETMT3d180 57 253 41 187 37 251 1.4 1.5

The ratios between ∆Hm1 and ∆Hc are very similar for PETC and PETM. The ratios

between ∆Hm1 and ∆Hm2 are also very similar.

∆Hm1 and ∆Hc were plotted against the exposure time above Tg and the result is

presented in Figure 49 to Figure 56.

For PETC there seems to be an increasing trend in ∆Hc depending on the exposure

time above Tg for the samples exposed to dyeing at 135°C for 60 minutes (Figure

52).

61

For PETM there seems to be a decreasing trend in ∆Hm1 depending on the exposure

time above Tg for the samples exposed to dyeing at 135°C for 60 minutes (Figure

54).

FIGURE 49 HEAT OF MELTING FOR PETC SAMPLES EXPOSED TO ONE DYEING CYCLE. FOR

CLARITY, ∆HM1 FOR BATH P AND BATH D HAVE BEEN EXAGGERATED BY -15 J/G AND 15

J/G, RESPECTIVELY.

FIGURE 50 HEAT OF MELTING FOR PETC SAMPLES EXPOSED TO ONE, THREE AND FIVE

DYEING CYCLES IN BATH D. FOR CLARITY, ∆HM1 FOR 135°C, 30 MIN AND 135°C, 60 MIN

HAVE BEEN EXAGGERATED BY 15 J/G.

20

30

40

50

60

70

80

0 50 100 150 200 250

Hea

t of

mel

tin

g,

∆H

m1 [

J/g

]


105°C

120°C

135°C

105°C

120°C

135°C

105°C

120°C

135°C

Bath d

Bath l

Bath p

30

40

50

60

70

80

0 100 200 300 400 500 600

Hea

t of

mel

tin

g,

∆H

m1 [

J/g

]


105°C, 30 min

105°C, 60 min

135°C, 30 min

135°C, 60 min

62

FIGURE 51 HEAT OF CRYSTALLISATION FOR PETC SAMPLES EXPOSED TO ONE DYEING

CYCLE. FOR CLARITY, ∆HC FOR BATH P AND BATH D HAVE BEEN EXAGGERATED BY -15 J/G

AND 15 J/G, RESPECTIVELY.

FIGURE 52 HEAT OF CRYSTALLISATION FOR PETC SAMPLES EXPOSED TO ONE, THREE AND

FIVE DYEING CYCLES IN BATH D. FOR CLARITY, ∆HC FOR 135°C, 30 MIN AND 135°C, 60

MIN HAVE BEEN EXAGGERATED BY 15 J/G.

FIGURE 53 HEAT OF MELTING FOR PETM SAMPLES EXPOSED TO ONE DYEING CYCLE. FOR

CLARITY, ∆HM1 FOR BATH 1 AND BATH 3 HAVE BEEN EXAGGERATED BY -15 J/G AND 15

J/G, RESPECTIVELY.

0

10

20

30

40

50

60

0 50 100 150 200 250

Hea

t of

cry

stall

isati

on

, ∆

Hc

[J/g

]


105°C

120°C

135°C

105°C

120°C

135°C

105°C

120°C

135°C

Bath d

Bath l

Bath p

0

10

20

30

40

50

60

0 100 200 300 400 500 600Hea

t of

cry

stall

isati

on

, ∆

Hc

[J/g

]


105°C, 30 min

105°C, 60 min

135°C, 30 min

135°C, 60 min

20

30

40

50

60

70

80

0 50 100 150 200 250

Hea

t of

mel

tin

g,

∆H

m1 [

J/g

]


105°C

120°C

135°C

105°C

120°C

135°C

105°C

120°C

135°C

Bath d

Bath l

Bath p

63

FIGURE 54 HEAT OF MELTING FOR PETM SAMPLES EXPOSED TO ONE, THREE AND FIVE

DYEING CYCLES IN BATH D. FOR CLARITY, ∆HM1 FOR 135°C, 30 MIN AND 135°C, 60 MIN

HAVE BEEN EXAGGERATED BY 15 J/G.

FIGURE 55 HEAT OF CRYSTALLISATION FOR PETM SAMPLES EXPOSED TO ONE DYEING

CYCLE. FOR CLARITY, ∆HC FOR BATH P AND BATH D HAVE BEEN EXAGGERATED BY -15 J/G

AND 15 J/G, RESPECTIVELY.

FIGURE 56 HEAT OF CRYSTALLISATION FOR PETM SAMPLES EXPOSED TO ONE, THREE AND

FIVE DYEING CYCLES IN BATH D. FOR CLARITY, ∆HC FOR 135°C, 30 MIN AND 135°C, 60

MIN HAVE BEEN EXAGGERATED BY 15 J/G.

30

40

50

60

70

80

0 100 200 300 400 500 600

Hea

t of

mel

tin

g,

∆H

m1 [

J/g

]


105°C, 30 min

105°C, 60 min

135°C, 30 min

135°C, 60 min

0

10

20

30

40

50

60

0 50 100 150 200 250

Hea

t of

cry

stall

isati

on

, ∆

Hc

[J/g

]


105°C

120°C

135°C

105°C

120°C

135°C

105°C

120°C

135°C

Bath d

Bath l

Bath p

0

10

20

30

40

50

60

0 100 200 300 400 500 600

Hea

t of

cry

stall

isati

on

, ∆

Hc

[J/g

]


105°C, 30 min

105°C, 60 min

135°C, 30 min

135°C, 60 min

64

4.5.1. DSC CURVES FOR PETC SAMPLES

In Figure 57 to Figure 65 DSC curves for PETC samples are presented. In all fig-

ures it can be seen that during cooling dyed samples exhibit crystallisation peaks

different from the PETC Ref.

FIGURE 57 OVERLAID DSC CURVES FOR PETC SAMPLES EXPOSED TO DYEING AT 105°C

FOR 30 MIN IN ALL BATH COMPOSITIONS.



65







66







67



4.5.2. DSC CURVES FOR PETM SAMPLES

In Figure 66 to Figure 74 DSC curves for PETM samples are presented. Just as for

the PETC samples, changes in the crystallisation peaks can be observed during

cooling.

FIGURE 66 OVERLAID DSC CURVES FOR PETM SAMPLES EXPOSED TO DYEING AT 105°C


68







69







70





4.6. DISSOLVING OF PET FABRICS The PET fabrics used within this study could not be successfully dissolved in the

proposed solvents: DMSO + lithium bromide, THF, and chloroform. Due to this,

molecular weight determination through SEC has not been possible to perform.

71

5. DISCUSSION AND ANALYSIS In this section the results will be analysed and discussed in relation to the literature

review with the purpose of finding answers to the research questions. Also, the

experimental methods used within this Master thesis will be discussed.

5.1. WEIGHT DIFFERENCES The results indicate that the percentage weight differences observed in PETC sam-

ples are mostly affected by the number of dyeing cycles. The average percentage

weight differences of the samples exposed to multiple dyeing cycles in 135°C seem

to increase proportionally to the number of dyeing cycles. For example, the weight

difference of PETCT3d60×3 is approximately three times the weight difference for

PETCT3d60. For PETCT3d60×5 the difference is approximately five times the

weight difference for PETCT3d60. However, for the samples dyed in 105°C the

differences are not as large.

As can be seen in Figure 75, the exposure time above Tg does not seem to cause as

big differences in the weight as the number of dyeing cycles. It seems that the

number of cycles and hence the concentration of chemicals that the samples have

been exposed are the critical factors. PETCT3d30×3 and PETCT3d180 have been

exposed 240 and 230 min respectively, yet the average weight difference is larger

for PETCT3d30×3. Temperature along with number of dyeing cycles seems to be

the main influencing parameters. Similar weight differences seem to be the case for

PETM samples, as shown in Figure 76.

FIGURE 75 AVERAGE PERCENTAGE WEIGHT DIFFERENCE PLOTTED AGAINST EXPOSURE

TIME ABOVE TG FOR PETC SAMPLES. FOR CLARITY, AVERAGE WEIGHT DIFFERENCES FOR

SAMPLES DYED IN 135°C HAVE BEEN EXAGGERATED BY 1%.

0

0.5

1

1.5

2

2.5

3

0 100 200 300 400 500 600

Aver

ag

e w

eig

ht

dif

fere

nce

[%

]


105°C, 30 min

105°C, 60 min

105°C, 180 min

135°C, 30 min

135°C, 60 min

135°C, 180 min

72

FIGURE 76 AVERAGE PERCENTAGE WEIGHT DIFFERENCE PLOTTED AGAINST EXPOSURE

TIME ABOVE TG FOR PETM SAMPLES. FOR CLARITY, AVERAGE WEIGHT DIFFERENCES FOR

SAMPLES DYED IN 135°C HAVE BEEN EXAGGERATED BY 1%.

The samples dyed in 105°C and 135°C has been exposed to the same concentra-

tions of dye stuff and auxiliary chemicals. Yet, the weight differences are larger for

the higher temperature. Two potential explanations behind this observation may be

suggested. First, it can be an effect of increased hydrophilicity due to formation of

more hydrophilic end-groups if chain scission has occurred during the dyeing pro-

cess. Second, it could be due to access to the fibre interior since the higher temper-

ature should cause increased mobility in the polymers. This could lead to a higher

concentration of auxiliary chemicals diffusing into the fibres during dyeing.

5.1.1. VACUUM DRYING

The aim of vacuum drying was to investigate the reason behind the weight increase

observed after dyeing. As suggested previously the increase could be an effect of

increased hydrophilicity, the amount of chemicals present in the fabrics, or a com-

bination of both.

PETC samples exhibit a percentage weight decrease after vacuum drying, which

was expected. On the other hand, the vacuum drying and weighing of the PETM

samples resulted in inconclusive and unexpected results. Some samples exhibited a

percentage weight increase while other samples exhibited a percentage weight

decrease. The error of the scales that were used is 0.0001 g and since five signifi-

cant figures were noted, the measurement error is very low. This is therefore not

suggested to be the reason behind the inconclusive result.

The result of the weighing after vacuum drying and the result of the demand absor-

bency test might be related. Therefore, a correlation analysis of the values obtained

through these two tests was performed.

For PETC samples a negative correlation between DAC and the percentage weight

difference after vacuum drying was found. The correlation coefficient established

is -0.416, which is considered a moderate correlation. The correlation means that as

the weight difference becomes smaller so does the demand absorbency capacity.

The complete correlation analysis is shown in Appendix XII, Table 23. This is

0

0.5

1

1.5

2

2.5

3

0 100 200 300 400 500 600

Aver

ag

e w

eig

ht

dif

fere

nce

[%

]


105°C, 30 min

105°C, 60 min

105°C, 180 min

135°C, 30 min

135°C, 60 min

135°C, 180 min

73

shown graphically in the scatter plot in Figure 77. The potential removal of mois-

ture by vacuum drying is supposed to indicate increased hydrophilicity. The DAC

is also supposed to indicate increased hydrophilicity, since an increased concentra-

tion of hydrophilic end-groups is assumed to result in increased ability to absorb

moisture. Sanders and Zeronian (1982) suggested that moisture related properties

similar to DAC are not sensitive enough to indicate hydrolysis. However, the cor-

relation between DAC and the changes in weight due to vacuum drying contributes

to the cenclusion that dyeing has caused some kind of changes in the PET polymer.

FIGURE 77 SCATTER PLOT OF AVERAGE DAC AGAINST AVERAGE WEIGHT DIFFERENCE

DUE TO VACUUM DRYING FOR PETC SAMPLES. TREND LINE REPRESENTS A MODERATE

NEGATIVE CORRELATION.

No correlation was found for PETM samples (Table 26 in Appendix XIV). What

can be said about the result of the vacuum drying and the PETM fibres is that for

the three different bath compositions and for temperature 105°C and 120°C the

average weight difference follows some sort of patterns. However, explanations for

this have not been found.

5.2. TENSILE PROPERTIES It has been suggested by others that dyeing does not cause large enough changes in

the PET polymer that affects the mechanical properties (Smole & Zipper 2002).

This work shows significant decreases in breaking strength and elongation at break

in multifilament yarns consisting of conventional PET as well as microfibre PET.

When looking into the samples with a breaking strength significantly different

from the reference, there are more significant values among the PETM samples

(eight) than among the PETC samples (four). Out of the significantly different

PETM samples, all samples except one have been exposed to dyeing in 135°C. For

PETC, three of the significantly different samples have been exposed to dyeing at

120°C. It seems as there may be a difference between the effects of temperature

between the two filament titer. The samples with significantly different breaking

strength exhibit a lower breaking strength than the reference samples. This is the

case for both PETC and PETM. It should be noted that the PETC samples that did

not have a breaking strength significantly different from PETC Ref in most cases

1.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

-0.3 -0.25 -0.2 -0.15 -0.1 -0.05 0

Aver

ag

e D

eman

d A

bsr

ob

an

cy

Cap

aci

ty [

g/g

]

Average weight difference [%]

74

(all but four) exhibited a lower breaking strength than the reference. All dyed

PETM samples exhibited a lower breaking strength than PETM Ref.

The Young’s moduli of PETC samples and PETM samples have been affected by

dyeing. All PETC samples with a modulus significantly different from the reference

exhibit higher modulus. Among the significantly different PETM samples both

higher and lower moduli are observed. The difference between PETC Ref and the

sample with the highest moduli is 0.020 N/tex and for PETM the difference is 0.017

N/tex. No correlations between dyeing parameters and Young’s modulus have been

found for any of the PET fabrics. It has been suggested that Young’s modulus of

PET yarn is affected by degree of orientation rather than degree of crystallinity

(Gupta & Kumar 1981b). It has also been suggested that chain scission of PET

result in shorter chains which can disentangle and take a more ordered structure

(Allen, Edge & Mohammadian 1991). This could potentially explain the increases

observed. However, since both higher and lower moduli have been observed it is

difficult to draw any conclusions on what the reason behind this.

5.3. CORRELATIONS AND RELATIONSHIPS Pearson correlation coefficients have been established using Minitab, to find indi-

cations of linear relationships between the investigated variables and properties.

Complete results from Minitab are presented in Appendix XIII for PETC samples

and Appendix XIV for PETM samples.

5.3.1. THE EFFECTS OF EXPOSURE TIME ABOVE TG

For PETC no significant correlations between exposure time above Tg and any of

the tensile or demand absorbency properties have been found. For PETM, however,

significant correlations have been found between exposure time above Tg and

breaking strength and elongation at break. Between exposure time and breaking

strength a negative correlation of -0.584 have been found. Between exposure time

and elongation at break the correlation is also negative, being -0.393.

For PETM samples a significant negative correlation of -0.406 (moderate) has been

found between the exposure time above Tg and ∆Hm1, while no significant correla-

tion between these variables was found for PETC samples. One possible explana-

tion behind this correlation could be that dyeing means exposure to temperatures

above Tg after the primary crystallisation. Gupta and Kumar (1981a) suggested that

this may result in a decreased degree of crystallinity because the imperfections in

the crystalline phase diffuse into the amorphous phase. The extent of such diffusion

could possibly be higher with increased exposure time. This would also explain the

negative correlations between exposure time above Tg and the mechanical proper-

ties, since degree of crystallinity is known to affect both breaking strength and

elongation at break.

5.3.2. THE EFFECTS OF DYEING TEMPERATURE

The correlation analysis showed only three significant correlations between dyeing

temperature and investigated properties. First, correlations between dyeing temper-

ature and demand absorbency capacity have been found for both PETC and PETM.

However, the correlations are of different kind. For PETC a moderate positive cor-

relation between dyeing temperature and DAC was found. For PETM a strong

75

negative correlation between dyeing temperature and DAC was found. The fila-

ment titer in combination with the dyeing temperature seems to be a critical factor

for the changes of the demand absorbency properties.

A weak positive correlation was also found between dyeing temperature and ∆Hc

for PETC samples. This means that increased dyeing temperature will result in in-

creased ∆Hc. A higher value of ∆Hc indicates a faster crystallisation process than a

lower value and changes in crystallisation rate has been shown to depend on degree

of chain scission after re-processing of PET (López et al. 2014). This correlation

could possibly indicate that chain scission has occurred during dyeing when the

exposure times are longer.

5.3.3. DSC RESULTS, TENSILE PROPERTIES AND DEMAND ABSORBENCY

For PETC samples a negative correlation of -0.666 between breaking strength and

heat of crystallisation (∆Hc) was found, this is shown graphically in Figure 78. The

PETC samples that exhibited the most obvious decreases in breaking strength were

found to have among the higher values of ∆Hc. The DSC results show that the

PETC samples exhibiting the highest values of ∆Hc, also exhibit sharper and less

wide crystallisation peaks. This indicates that the breaking strength is related to the

rate of crystallisation, which has been suggested to be related to chain scission

(López et al. 2014). If chain scission has occurred during dyeing it would be ex-

pected that crystallisation occurs faster and easier. Between elongation at break and

∆Hc a negative correlation of -0.407 has been observed.

FIGURE 78 AVERAGE BREAKING STRENGTH PLOTTED AGAINST ∆HC FOR PETC SAMPLES.

TREND LINE REPRESENTS A STRONG NEGATIVE CORRELATION BETWEEN THE TWO VARIA-

BLES.

A negative correlation of -0.526 has been observed between DAC and breaking

strength for PETC. This means that the higher the breaking strength, the lower the

DAC will be. Putting this in relation to the correlation between breaking strength

and ∆Hc, indicates that chain scission may have occurred during dyeing. DAC is

expected to be partially affected by hydrophilicity.

For PETM samples a positive correlation of 0.502 between breaking strength and

∆Hm1 was found to be significant. Also, a positive correlation of 0.642 between

elongation at break and ∆Hm1 was found significant. This is shown graphically in

0

1

2

3

4

5

6

7

8

30 32 34 36 38 40 42 44 46 48 50

Aver

ag

e b

reak

ing

str

eng

th [

N]

Heat of crystallisation [J/g]

76

Figure 79 and Figure 80, respectively. Regarding ∆Hc of PETM, only one correla-

tion was found: a weak negative correlation between ∆Hc and MAR.

FIGURE 79 SCATTER PLOT OF ∆HM1 AGAINST AVERAGE BREAKING STRENGTH FOR PETM

SAMPLES. TREND LINE REPRESENTS A STRONG POSITIVE CORRELATION BETWEEN THE TWO

VARIABLES.

FIGURE 80 SCATTER PLOT OF ∆HM1 AGAINST AVERAGE ELONGATION AT BREAK FOR PETM

SAMPLES. TREND LINE REPRESENTS A STRONG POSITIVE CORRELATION BETWEEN THE TWO

VARIABLES.

5.4. FTIR RESULTS The calculated absorbance ratios do not differ very much. Also, as can be seen in

the spectra presented in Appendix XI (PETC) and Appendix XII (PETM) the differ-

ences between reference spectrum and sample spectra are quite small. However,

some spectral changes may indicate degradation and therefore some further discus-

sion around this is in place.

53

54

55

56

57

58

59

60

61

62

63

4.3 4.4 4.5 4.6 4.7 4.8 4.9

Hea

t of

mel

tin

g [

J/g

]

Average breaking strength [N]

53

54

55

56

57

58

59

60

61

62

63

23 23.5 24 24.5 25 25.5 26 26.5 27

Hea

t of

mel

tin

g [

J/g

]

Average elongation at break [%]

77

Chain scission through hydrolysis has been shown to result in an intensity decrease

at the peak related to C=O bonds (Sammon, Yarwood & Everall 2000; Donelli et

al. 2010). For the PET used in this study the peak related to C=O was detected at

1712 cm-1

, which is in agreement with previously reported results for semi-

crystalline PET. For both PETC and PETM decreased intensity and lower absorb-

ance ratios at this particular wavenumber have been observed. It is most clear in

PETC, where all dyed samples exhibit absorbance ratios lower than the ratio for the

PETC Ref. The most obvious decreases are observed in the samples exposed to

three and five dyeing cycles in the bath containing all auxiliary chemicals. This

seems to be the case for samples exposed to both 105°C and 135°C. For PETM, the

absorbance ratios provide less conclusive results. However, the most obvious de-

creases are observed in samples dyed in 135°C, exposed to five dyeing cycles. It is

therefore proposed that the number of dyeing cycles is a critical factor, as well as

the exposure time above Tg. For both PETC and PETM strong negative correlations

was found between exposure time above Tg and the absorbance ratio (1712/1409).

This means that as the exposure time increases the absorbance ratio decreases. The

correlation coefficients found were quite similar, -0.635 for PETC and -0.632 for

PETM.

One very obvious change in spectral data was found for PETMT3d60×5, see Figure

81. Out of all the PETM samples this is the sample exposed to dyeing for the long-

est time above Tg. This sample has also been dyed five times, meaning that the

concentration of the auxiliary chemicals that the sample has been exposed to is

among the highest. These peaks could indicate hydrolysis. Similar peaks at similar

wavenumbers were presented by Sammon, Yarwood and Everall (2000) in hydro-

lysed PET films.


135°C FOR DYEING CYCLES OF 60 MIN.

Looking more closely within these wavenumbers it can be observed that there are

also differences for the PETM samples dyed in 135°C for 30 minutes. The changes

are not at all as apparent but there are differences due to the number of dyeing cy-

28

49

29

17

0

0.025

0.05

0.075

0.1

275028502950305031503250

Ab

sorb

an

ce

Wavenumber [cm-1]

Reference

PETM T3 p 60

PETM T3 l 60

PETM T3 d 60

PETM T3 d 60×3

PETM T3 d 60×5

78

cles, which can be seen in Figure 82. This has not been observed in PETC samples

exposed to the same conditions.


135°C FOR DYEING CYCLES OF 30 MIN.

Spectral changes were observed between 1420 cm-1

and 1620 cm-1

. According to

Chen, Hay and Jenkins (2012) spectral changes in this area is related to crystallisa-

tion. The peak at 1578 cm-1

has increased in intensity due to dyeing in both PETC

and PETM samples which can be seen in Figure 42 to Figure 47 in section 4.4. Fou-

rier-Transform Infrared Spectroscopy, and Figure 83 below (moved from section

4.4.). Chen, Hay and Jenkins (2012) observed intensity decrease at this wave-

number as crystallinity increased, and thereby it has been suggested that this is

peak related to the amorphous fraction of PET. Peaks at 1470 cm-1

and 1471 cm-1

has been shown to increase in intensity when crystallinity increases (Donelli et al.

2010; Badia et al. 2012; Chen, Hay & Jenkins 2012). A small intensity increase

can be observed after dyeing at wavenumber 1469 cm-1

.

0

0.02

0.04

0.06

0.08

0.1

275028502950305031503250

Ab

sorb

an

ce

Wavenumber [cm-1]

PETM Ref

PETM T3 p 30

PETM T3 l 30

PETM T3 d 30

PETM T3 d 30×3

PETM T3 d 30×5

79


FOR 30 MINUTES.

It is somewhat unclear what these changes between 1420 cm-1

and 1620 cm-1

actu-

ally indicate. There is a risk that the differences could be due to noise since they

are quite small, but it is also quite clear that these changes depend on the number of

dyeing cycles. Therefore it is suggested that these changes should be further stud-

ied in future work.

5.4.1. TRANS-GAUCHE RELATIONSHIPS

Changes in crystallinity can be observed through FTIR and by investigating chang-

es in absorbance at wavenumber associated with trans-gauche couples (Miyake

1959; Donelli et al. 2010). For PETC samples, only significant positive correlations

between the investigated trans-gauche couples have been found. A strong correla-

tion of 0.923 was found between 847 cm-1

(trans) and 898 cm-1

(gauche). A mod-

erate correlation of 0.429 was found between 1339 cm-1

(trans) and 1371 cm-1

(gauche). When the crystallinity increases it would be expected to find negative

correlations between trans and gauche peaks, since the trans peak intensity would

increase while the gauche peak would decrease (Miyake 1959).

For PETM a strong negative correlation of -0.637 has been found between the max-

imum absorbance at 1340 cm-1

(trans – crystalline) and 1371 cm-1

(gauche – amor-

phous), which is expected if the degree of crystallinity have increased (ibid.). For

the suggested trans-gauche couple at 847 cm-1

and 898 cm-1

a positive correlation

of 0.529 has been found. Hence, the results are somewhat inconclusive. It would be

expected to observe similar correlations for the two different couples.

5.5. DSC RESULTS The result of the DSC shows no large shift in melting temperatures. For PETC the

melting temperatures observed during the first heating cycle is in the range of 252 -

255°C. For the same heating cycle, the range observed in PETM is 252 - 254°C.

The variation in maximum peak crystallisation temperature is larger. For PETC the

crystallisation temperatures are found in the temperature range from 175°C to

190°C. For PETM the temperature range is from 179°C to 191°C. When comparing

maximum and minimum values the differences are larger for PETC than for PETM.

14

49

14

69

15

34

15

78

1

58

5

0

0.05

0.1

0.15

0.2

13001400150016001700

Ab

sorb

an

ce

Wavenumber [cm-1]

PETC Ref

PETC T1 p 30

PETC T1 l 30

PETC T1 d 30

PETC T1 d 30×3

PETC T1 d 30×5

80

The difference between the highest and lowest observed ∆Hm1 for PETC is 9 while

for PETM it is 8. This is not at remarkable difference. However, the difference be-

tween the highest and lowest observed ∆Hc for PETC is 13 while for PETM it is 8.

This indicates that the filament titer affects these changes. The results also indicate

that the amorphous parts of the polymer are more affected by dyeing than the crys-

talline part, since the changes observed in melting behaviour are not as large. This

is in agreement with the suggestion that hydrolysis takes place in the amorphous

fractions of PET (Pirzadeh, Zadhoush & Haghighat 2007).

The crystallisation peaks of the reference samples for both PETC and PETM are

wider than the peaks of the dyed samples. Changes in crystallisation peaks have

been observed after re-processing of PET by means of injection moulding (López

et al. 2014) and have been concluded to be an effect of chain scission. The largest

changes seem to have occurred after dyeing in the bath containing all of the auxil-

iary chemicals. Also, the number of dyeing cycles seems to contribute to the

changes in the crystallisation peaks.

The melting peaks observed during the first heating cycle has also been somewhat

altered due to dyeing. However, these changes are not as prominent as the observed

changes indicating altered crystallisation behaviour. The lowest values of ∆Hm1 for

both PETC and PETM are observed in samples exposed to five dyeing cycles in

135°C.

The DSC result shows that there is a 2% difference in degree of crystallinity be-

tween PETC Ref and PETM Ref. The higher degree of crystallinity was observed in

PETM and was calculated to be 43%. The degree of crystallinity in PETC was cal-

culated to be 41%. Since this is not a large difference it is not suspected to be the

main reason behind the differences observed in the two fabrics after dyeing.

5.6. METHODOLOGY In this section the experimental methods used in this study are discussed. Also,

alternative possible methods are presented in the discussion.

5.6.1. DEMAND ABSORBENCY TEST

The test method used for investigating surface properties in terms of demand ab-

sorbency capacity and maximum absorption rate is appropriate to discuss. EN ISO

9073-12:2002 is a standard developed for testing of non-woven textile materials

but in this case it was used for woven fabrics. Also, it is not only the surface prop-

erties of the fibres that affect the results. Capillary forces play a vital role for the

interaction with water and the absorption behaviour and these forces are affected

by the woven structure and its density.

It is also important to mention that the auxiliary chemicals used in dyeing contain

chemical compounds with surfactant properties. The samples were only rinsed with

water after dyeing and therefore there is a possibility that residuals of auxiliary

chemicals are present on the fabric surface and the surface of the fibres. Obviously

this could have an effect on the outcome of the test.

One alternative method that could have been used for investigating possible chang-

es in hydrophilicity is contact angle measurement. This method has been used by

81

others to investigate hydrophilicity of modified PET films (Donelli et al. 2010).

Just as with the demand absorbency test, contact angle measurement is affected by

fabric structure. Wicking test on the multifilament yarns could have been per-

formed. Results from such a test may be more closely related to changes in the

polymer since any dependence of fabric structure could be excluded.

5.6.2. DSC

It is of importance to point out that only one fabric duplicate for each sample was

characterised using DSC. It would have been preferable to characterise more fabric

duplicates for each sample and thereby establish average values. That would have

created a possibility to statistically analyse the data and to establish if there are any

statistical differences between the reference samples and the dyed samples. Instead,

the data obtained from the DSC has now been used for correlation analysis with the

aim to explain changes in mechanical and moisture related properties.

DSC can provide data on the degree of crystallinity but the degree of orientation

cannot be estimated based on DSC results. The degree of orientation has been

shown to affect both elongation at break and tenacity (Gupta & Kumar 1981c) and

therefore it would be of interest to use methods providing information on this mat-

ter.

5.6.3. FTIR

As stated previously, the results of the FTIR when it comes to trans-gauche cou-

ples are somewhat inconclusive. Raman spectroscopy could possibly bring clarifi-

cation to the FTIR results. These methods are sometimes used as a complement to

one and other.

5.7. RECYCLABILITY OF DYED PET FABRICS One requirement for recycling that the PET polymer should meet is a melting tem-

perature above 240°C (Awaja & Pavel 2005). DSC results show that the melting

temperatures for the fabrics used within this Master thesis remain at or above

252°C after dyeing. Therefore, this requirement could be considered fulfilled.

Considering problematic contaminants the pH-regulator Neutracid BO 45 contain-

ing acetic acid should be discussed. The weight differences observed in both PETC

and PETM suggest that there are auxiliary chemicals present in the fabrics after

dyeing. It has not been investigated if the chemicals are present in the polymers or

at the surface. However, if there are residual auxiliary chemicals in the polymers

these are probably not to be removed by additional washing steps. This could cause

problems since acetic acid act as a catalyst in the chain scission reactions of PET

(Al-Sabagh et al. 2015; Awaja & Pavel 2005) and chain scission reactions are

known to occur during thermo-mechanical recycling of PET.

Based on the results it is difficult to conclude the reason behind the weight increase

observed after dyeing. It is possible that this is due to both increased hydrophilicity

and the presence of auxiliary chemicals. It could also be an effect of changes of the

crystalline fraction, which would show as density changes. The two former expla-

nations could cause problems in recycling. Increased hydrophilicity could probably

be solved with proper pre-drying before re-processing, which is usually done be-

82

fore recycling of bottle-grade PET as well. The potential problem of auxiliary

chemicals may be trickier to solve. It has been demonstrated that dye can be ex-

tracted out of dyed PET fabrics (e.g. Andersson Drugge & Svensson 2016) but

investigations with focus on auxiliary chemicals have not been found. This pro-

vides a route for further research.

It is the author’s opinion that the experimentally obtained results do not provide

conclusive evidence that exhaust dyeing negatively affects the possibility to recy-

cle PET textiles through thermo-mechanical methods. The changes observed due to

exhaust dyeing are not as evident as expected. Chain scission is indicated by the

decreased mechanical properties, crystallisation behaviour, and FTIR results and

this could potentially be problematic in a thermo-mechanical recycling process.

Since research on thermo-mechanical recycling of fibre-grade PET is limited it is

somewhat difficult to connect the results obtained through this work actual recy-

cling. It is believed that this Master thesis provides good information that should be

further researched in the context of thermo-mechanical recycling, in order to find

correlations between the observed changes and possible problems in a re-melt

spinning process.

When it comes recycling of post-consumer textile waste it is important to under-

stand that the dyeing process is just one factor that can affect the recyclability. This

research contributes to this area but further research regarding other processes as

well as exposure to possibly degrading situations is required. The dyeing process

alone cannot be pointed out as the reason why thermo-mechanical fibre-to-fibre

recycling is not used.

83

6. CONCLUSIONS In this section the research question are answered one by one, leading to a conclu-

sion presented in the end of the section.

- Is the polymer structure of PET affected by exhaust dyeing? If so, how is

the polymer structure affected? Can any dyeing parameters be identified

as critical?

Changes in heat of crystallisation as well as in heat of melting indicate that the

polymer structure is somewhat affected by the exhaust dyeing process. The results

indicate that the crystallisation rate has increased due to dyeing. This could be due

to formation of shorter chains during dyeing. The most obvious changes are ob-

served in samples dyed in the bath containing all auxiliary chemicals. Similar

changes are observed for all temperatures and exposure times. Therefore, it is sug-

gested that the bath composition and hence the auxiliary chemicals is one critical

factor considering how the polymer structure is affected.

The changes in spectral data also indicate that dyeing affects the polymer structure.

The spectral data indicate chain scission, but it should be mentioned that the differ-

ences have not been statistically evaluated. For both fabrics the most obvious

changes are observed in the samples dyed at 135°C for 60 minutes, five dyeing

cycles, in the bath containing all auxiliary chemicals. Negative correlations be-

tween exposure time above Tg and absorbance ratio (1712/1409) has been found

significant showing that the exposure time is also a critical factor, possibly affect-

ing chain scission.

- Are the tensile properties of PET affected by exhaust dyeing? If so, how

are the properties affected and which dyeing parameters are critical?

After exposure to exhaust dyeing breaking strength, elongation at break and

Young’s modulus are in some samples significantly different from the reference

samples.

Considering breaking strength, decreasing trends have been observed in both PETC

and PETM samples exposed to multiple dyeing cycles at 135°C. Based on the corre-

lation analyses it can be concluded that the exposure time above Tg seem to be a

critical factor negatively affecting breaking strength and elongation at break for the

investigated microfibre PET. No significant correlation could be found for PETC.

- Are the surface characteristics of PET affected by exhaust dyeing? If so,

how are the properties affected and which dyeing parameters are critical?

The surface characteristics in terms of demand absorbency capacity and maximum

absorption rate have been affected by exhaust dyeing. The changes in DAC were

shown to differ between the two different filaments. For PETC, the DAC increased

due to dyeing while for PETM the DAC decreased due to dyeing. The filament titer

seems to be a critical factor when considering this parameter.

Increased dyeing temperature resulted in higher DAC in PETC but in lower DAC

for PETM. These correlations were statistically significant. Therefore, it is sug-

gested that in addition to filament titer, dyeing temperature is also a critical factor.

84

- Are any changes induced by the exhaust dyeing process related to fila-

ment titer?

Filament titer seems to be related to changes induced by exhaust dyeing consider-

ing specific properties. First, the changes in demand absorbency properties seem to

be related to filament titer. Second, changes in the spectral data regarding the car-

bonyl bonds are more evident and conclusive in PETC samples, the PET with the

larger filament titer. However, changes in the spectral data (wavenumber 2800 cm-1

to 3000 cm-1

) are only observed in PETM, the PET with the smaller filament titer.

Both of these observations indicate chain scission. And third, the changes observed

in crystallisation behaviour are more prominent in the samples with a larger fila-

ment titer.

- Can changes induced by exhaust dyeing negatively affect the possibility to

recycle PET textiles through a thermo-mechanical process?

It is the author’s opinion that the results do not provide clear evidence that the ex-

haust dyeing process leads to changes that would negatively affect thermo-

mechanical recycling. More research is needed in order to completely answer this

research question.

The main purpose of this Master thesis is to investigate if exhaust dyeing of PET

compromises the possibility of thermo-mechanical recycling. The hypothesis that

this Master thesis is based on is: The polymer structure of PET is affected by the

exhaust dyeing process to such an extent that re-melt spinning is compromised.

Changes have been observed due to dyeing, however these changes were not as

large as expected. It is therefore concluded that the results does not provide conclu-

sive evidence that supports the hypothesis. Yet again, changes indicating degrada-

tion has been observed and it is the author’s opinion that the hypothesis should not

be rejected without further research. It should also be noted that the exposure time

above Tg and the auxiliary chemicals seem to be important factors considering

chain scission. Therefore, it is suggested that multiple dyeing cycles should be

applied with caution since this increases the exposure time as well as the exposure

to auxiliary chemicals.

85

7. FUTURE RESEARCH There are several different routes for further research, and these are presented in

the upcoming sections.

7.1. VARIETY OF PROCESSING CONDITIONS AND MATERIALS Even though many parameters have been investigated in this Master thesis there

are still interesting factors to look into. One additional parameter to look into

would be reduction clearing and how this affects the properties of dyed fabrics

exposed to different dyeing conditions. It would also be interesting to see if reduc-

tion clearing has any effects on the demand absorbency properties.

It would als be interesting to investigate multiple dyeing cycles in a bath contain-

ing only pH-regulator and in a bath containing pH-regulator and levelling agent.

This could further clarify the role of the auxiliary chemicals in the dyeing-induced

changes of PET.

Another parameter to investigate would be mixed material fabrics. PET fibres are

often mixed with other materials, e.g. cotton, and if these materials are dyed in

form of fabrics the PET fibres are exposed to the dyeing conditions of cotton and

vice versa. In dyeing of PET fabrics the dye bath is kept at pH between 4.5 and 6.

Dyeing of cotton however, is carried out in alkaline conditions.

7.2. RE-MELT SPINNING OF DYED FABRICS The results of this Master thesis have not provided clear evidence on if dyeing

compromise the possibility of thermo-mechanical recycling. Therefore, an obvious

route for further recycling would be to perform re-melt spinning of dyed fabric

samples. Such a research could possibly establish correlations between dyeing

parameters and the result of re-melt spinning. It would be of interest to investigate

if and how the auxiliary chemicals react and interfere in a recycling process like re-

melt spinning. The auxiliary chemicals may cause harm in such a process since the

process temperatures are higher than dyeing temperatures.

7.3. FURTHER CHARACTERISATION It has been shown that changes arising due to thermal treatment after the primary

crystallisation can depend on if the fabric is in a taut or a relaxed state during the

treatment. During the exhaust dyeing the fabrics are considered to be in a relaxed

state and therefore they may shrink. This would in extent possibly affect the tensile

properties of the yarns and therefore it would be of interest to investigate shrinkage

due to dyeing. Perhaps correlations between shrinkage and tensile properties as

well as processing parameters could be established.

Melt viscosity is considered an important property when PET products are to be

recycled, therefore it would be of great interest to investigate if this is affected by

dyeing or if residual chemicals from dyeing may affect this property.

It would be of great interest to determine the MW of the dyed samples compared to

the reference. The DSC result showed changes in the crystallisation peaks after

dyeing, and this may be due to chain scission. Also, the FTIR results indicate that

86

chain scission may have occurred. Measurement of the MW and MW distribution

would bring clarity to these results.

7.3.1. CHARACTERISATION OF OLIGOMERS

As stated in the literature review, PET oligomers can be formed due to degrading

chain scission reactions. It has also been observed that dyeing conditions do affect

the quantity of oligomers in PET fabrics (Recelj, Gorenšek & Žigon 2002). There-

fore, it would be interesting to study if oligomer distribution differs between the

PET samples exposed to the different dyeing conditions. Since the cyclic trimer

content seems to be approximately constant even after re-processing (Dulio et al.

1994) it is suggested that other oligomers are to be studied, e.g. larger linear oli-

gomers which have been suggested to indicate degradation. It would be interesting

to investigate this with the aim to find correlations to the results presented in this

thesis that indicate degradation.

Considering the cyclic oligomers, the author suggests that SEM should be used to

study the presence of cyclic oligomers on the fibre surface after dyeing. It has been

shown that the presence of such oligomers may affect moisture related properties.

Therefore, further research regarding oligomer on the fibre surface could help ex-

plain the changes in moisture related properties that have been observed in this

work.

87

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https://doi.org/10.1016/j.resconrec.2011.04.009

93

Appendix I. TUKEY TEST: BREAKING

STRENGTH FOR PETC Tukey Pairwise Comparisons

Grouping Information Using the Tukey Method and 95% Confidence

Factor N Mean Grouping

PETC T1 d 60 20 6,7000 A

PETC T2 p 30 20 6,6980 A

PETC T2 l 30 20 6,6855 A

PETC T1 p 30 20 6,6785 A

PETC Ref 20 6,6695 A

PETC T3 p 30 20 6,6690 A

PETC T1 p 180 20 6,6335 A

PETC T1 l 30 20 6,6275 A

PETC T1 l 60 20 6,6225 A

PETC T2 d 30 20 6,6220 A

PETC T1 d 180 20 6,6080 A

PETC T1 p 60 20 6,5855 A

PETC T3 l 30 20 6,5785 A

PETC T2 l 180 20 6,5785 A

PETC T3 d 60 20 6,5760 A

PETC T1 l 180 20 6,5660 A

PETC T1 d 60×5 20 6,5250 A

PETC T3 p 60 20 6,521 A B

PETC T2 d 180 20 6,521 A B

PETC T1 d 30×5 20 6,5085 A B

PETC T1 d 60×3 20 6,4865 A B

PETC T1 d 30 20 6,4770 A B

PETC T3 l 60 20 6,461 A B

PETC T1 d 30×3 20 6,4585 A B C

PETC T3 d 30×3 20 6,4480 A B C

PETC T3 p 180 20 6,4425 A B C

PETC T2 p 180 20 6,4335 A B C

PETC T3 l 180 20 6,4265 A B C

PETC T3 d 60×3 20 6,4215 A B C

PETC T3 d 30 20 6,4145 A B C

PETC T3 d 30×5 20 6,4125 A B C

PETC T3 d 180 20 6,3620 A B C

PETC T3 d 60×5 20 6,1680 B C

PETC T2 p 60 20 6,106 C

PETC T2 d 60 20 5,3410 D

PETC T2 l 60 20 5,1475 D

Means that do not share a letter are significantly different. The

reference is marked in bold. Samples significantly different from

the reference are marked in italic.

94

Appendix II. TUKEY TEST: BREAKING

STRENGTH FOR PETM Tukey Pairwise Comparisons



PETM Ref 20 4,8455 A

PETM T1 l 30 20 4,8130 A B

PETM T1 l 60 20 4,8000 A B

PETM T3 d 30 20 4,7850 A B C

PETM T1 d 30 20 4,7845 A B C

PETM T3 l 30 20 4,7815 A B C

PETM T1 d 60×5 20 4,7760 A B C D

PETM T2 d 180 20 4,7645 A B C D

PETM T1 d 30×5 20 4,7590 A B C D E

PETM T1 l 180 20 4,7540 A B C D E

PETM T2 d 60 20 4,7495 A B C D E

PETM T1 p 60 20 4,7450 A B C D E

PETM T2 l 60 20 4,7365 A B C D E

PETM T2 d 30 20 4,7305 A B C D E

PETM T1 p 30 20 4,7300 A B C D E

PETM T2 l 180 20 4,7300 A B C D E

PETM T2 l 30 20 4,7290 A B C D E

PETM T2 p 180 20 4,7285 A B C D E

PETM T2 p 30 20 4,7240 A B C D E

PETM T3 d 60 20 4,7185 A B C D E

PETM T1 d 30×3 20 4,7175 A B C D E

PETM T3 p 30 20 4,7140 A B C D E

PETM T1 d 60 20 4,7120 A B C D E

PETM T3 p 60 20 4,7060 A B C D E F

PETM T3 d 30×3 20 4,6890 A B C D E F

PETM T1 d 180 20 4,6885 A B C D E F

PETM T1 d 60×3 20 4,6790 A B C D E F

PETM T1 p 180 20 4,6340 A B C D E F G

PETM T3 l 60 20 4,6060 B C D E F G H

PETM T3 d 30×5 20 4,5840 C D E F G H

PETM T2 p 60 20 4,573 C D E F G H

PETM T3 p 180 20 4,5625 D E F G H

PETM T3 d 60×3 20 4,5480 E F G H

PETM T3 d 180 20 4,4930 F G H

PETM T3 l 180 20 4,4445 G H

PETM T3 d 60×5 20 4,4125 H



the reference are marked in bold italic.

95

Appendix III. TUKEY TEST: ELONGATION AT

BREAK FOR PETC

Tukey Pairwise Comparisons



PETCT3d60 20 20,115 A

PETCT3l180 20 19,820 A B

PETCT3l60 20 19,780 A B

PETCT3p30 20 19,690 A B C

PETCT3p60 20 19,430 A B C D

PETCT2l180 20 19,385 A B C D

PETCT3l30 20 19,370 A B C D

PETCT3d60×3 20 19,310 A B C D

PETCT3p180 20 19,275 A B C D E

PETC Ref 20 19,265 A B C D E

PETCT2l30 20 19,210 A B C D E

PETCT1p30 20 19,185 A B C D E

PETCT1p180 20 19,080 A B C D E F

PETCT2p30 20 19,050 A B C D E F G

PETCT1d180 20 19,020 A B C D E F G

PETCT2d180 20 19,005 A B C D E F G

PETCT1l60 20 18,915 A B C D E F G H

PETCT3d180 20 18,890 A B C D E F G H

PETCT2p180 20 18,815 A B C D E F G H

PETCT1l180 20 18,780 A B C D E F G H

PETCT1p60 20 18,760 A B C D E F G H

PETCT1d60 20 18,720 B C D E F G H

PETCT3d30×5 20 18,705 B C D E F G H

PETCT3d30 20 18,680 B C D E F G H

PETCT3d30×3 20 18,645 B C D E F G H

PETCT2d30 20 18,630 B C D E F G H

PETCT1l30 20 18,625 B C D E F G H

PETCT3d60×5 20 18,515 B C D E F G H

PETCT2p60 20 18,400 C D E F G H

PETCT1d30 20 18,205 D E F G H I

PETCT1d60×5 20 17,935 E F G H I

PETCT1d30×3 20 17,785 F G H I

PETCT1d60×3 20 17,770 F G H I

PETCT1d30×5 20 17,700 G H I

PETCT2d60 20 17,620 H I

PETCT2l60 20 16,995 I



the reference are marked in bold italic.

96

Appendix IV. TUKEY TEST: ELONGATION AT

BREAK FOR PETM

Tukey Pairwise Comparisons



PETM T3 p 30 20 26,515 A

PETM T3 l 30 20 26,460 A B

PETM T1 l 60 20 26,315 A B C

PETM T2 l 30 20 26,250 A B C D

PETM T2 d 60 20 26,215 A B C D

PETM T3 d 30×3 20 26,080 A B C D E

PETM T2 d 180 20 26,075 A B C D E

PETM T2 p 30 20 26,035 A B C D E

PETM T2 d 30 20 26,015 A B C D E

PETM T2 l 60 20 25,995 A B C D E

PETM T3 d 30 20 25,950 A B C D E F

PETM T2 p 180 20 25,820 A B C D E F

PETM T1 p 60 20 25,730 A B C D E F

PETM T3 p 60 20 25,620 A B C D E F G

PETM T1 p 180 20 25,575 A B C D E F G

PETM T1 l 180 20 25,497 A B C D E F G H

PETM T1 d 30×3 20 25,385 A B C D E F G H

PETM T1 d 30 20 25,375 A B C D E F G H

PETM T1 d 60×5 20 25,310 A B C D E F G H

PETM T1 d 60 20 25,205 A B C D E F G H

PETM T3 l 60 20 25,180 A B C D E F G H

PETM T3 d 60 20 25,155 A B C D E F G H

PETM T1 d 30×5 20 25,150 A B C D E F G H

PETM T3 d 30×5 20 25,090 A B C D E F G H

PETM T3 d 60×3 20 25,080 A B C D E F G H

PETM T3 p 180 20 24,970 A B C D E F G H I

PETM T2 l 180 20 24,735 A B C D E F G H I

PETM T1 d 180 20 24,730 A B C D E F G H I

PETM Ref 20 24,690 B C D E F G H I

PETM T1 d 60×3 20 24,510 C D E F G H I

PETM T2 p 60 20 24,470 D E F G H I

PETM T1 l 30 20 24,295 E F G H I

PETM T3 l 180 20 24,180 F G H I

PETM T1 p 30 20 23,910 G H I

PETM T3 d 180 20 23,715 H I

PETM T3 d 60×5 20 23,260 I



the Reference are marked in bold italic.

97

Appendix V. TUKEY TEST: YOUNG’S MODU-

LUS FOR PETC Tukey Pairwise Comparisons



PETC T2 p 30 20 0,05038 A

PETC T1 l 60 20 0,04979 A

PETC T1 l 30 20 0,04944 A

PETC T1 p 180 20 0,04795 A B

PETC T1 l 180 20 0,04782 A B

PETC T3 p 180 20 0,04689 A B C

PETC T1 d 30 20 0,04680 A B C

PETC T3 d 180 20 0,04458 A B C D

PETC T3 p 60 20 0,04272 A B C D E

PETC T3 d 30×3 20 0,04250 A B C D E F

PETC T3 d 60×5 20 0,04134 B C D E F G

PETC T2 d 60 20 0,03992 B C D E F G H

PETC T1 d 30×3 20 0,03951 C D E F G H

PETC T1 d 60 20 0,039419 C D E F G H

PETC T2 p 60 20 0,03925 C D E F G H

PETC T1 d 60×3 20 0,03906 C D E F G H

PETC T1 d 60×5 20 0,03746 D E F G H I

PETC T3 p 30 20 0,03726 D E F G H I

PETC T2 d 180 20 0,03723 D E F G H I

PETC T2 p 180 20 0,03657 D E F G H I J

PETC T3 d 60×3 20 0,03644 E F G H I J

PETC T2 l 60 20 0,03616 E F G H I J

PETC T3 d 30 20 0,036067 E F G H I J

PETC T3 l 180 20 0,03520 E F G H I J

PETC T3 d 60 20 0,03464 F G H I J

PETC T1 d 30×5 20 0,03451 F G H I J

PETC T3 d 30×5 20 0,03428 G H I J

PETC T2 d 30 20 0,03422 G H I J

PETC T2 l 30 20 0,03410 G H I J

PETC T3 l 60 20 0,03404 G H I J

PETC T3 l 30 20 0,03331 G H I J

PETC T1 p 60 20 0,033190 H I J

PETC T1 p 30 20 0,03052 I J

PETC T2 l 180 20 0,03023 I J

PETC Ref 20 0,030075 I J

PETC T1 d 180 20 0,02906 J



the reference are marked in bold italic above.

98

Appendix VI. TUKEY TEST: YOUNG’S MODU-

LUS FOR PETM Tukey Pairwise Comparisons



PETM T2 p 180 20 0,06985 A

PETM T1 d 60 20 0,06918 A B

PETM T1 d 60*5 20 0,06493 A B C

PETM T2 p 30 20 0,06386 A B C D

PETM T3 d 30*3 20 0,06378 A B C D

PETM T2 l 60 20 0,06361 A B C D

PETM T2 p 60 20 0,06272 A B C D E

PETM T2 l 180 20 0,05989 A B C D E F

PETM T1 d 60*3 20 0,05980 A B C D E F

PETM T3 d 180 20 0,05925 A B C D E F G

PETM T3 d 30 20 0,05744 A B C D E F G H






PETM T1 d 30*5 20 0,05476 B C D E F G H I J

PETM T1 p 180 20 0,05469 B C D E F G H I J

PETM T3 d 30*5 20 0,05372 C D E F G H I J K

PETM Ref 20 0,05339 C D E F G H I J K

PETM T3 l 30 20 0,05333 C D E F G H I J K



PETM T3 d 60*3 20 0,04989 D E F G H I J K

PETM T1 p 30 20 0,04879 E F G H I J K

PETM T1 l 30 20 0,04760 F G H I J K L

PETM T3 d 60*5 20 0,04634 F G H I J K L

PETM T2 d 60 20 0,04525 F G H I J K L

PETM T1 d 30 20 0,04452 G H I J K L

PETM T3 p 60 20 0,04350 H I J K L

PETM T1 d 30*3 20 0,04250 I J K L

PETM T2 l 30 20 0,04240 I J K L

PETM T2 d 30 20 0,04168 I J K L

PETM T1 l 180 20 0,04018 J K L

PETM T1 p 60 20 0,03896 K L

PETM T3 l 180 20 0,03307 L



the Reference are marked in italic above.

99

Appendix VII. TUKEY TEST: DEMAND ABSOR-

BENCY CAPACITY FOR PETC Tukey Pairwise Comparisons



PETCT2d60 4 1,800 A

PETCT3d180 4 1,6500 A B

PETCT3d30×5 4 1,480 A B C

PETCT2p180 4 1,468 A B C

PETCT2l60 4 1,4525 A B C

PETCT2l30 4 1,4325 A B C

PETCT2p60 4 1,432 A B C

PETCT2p30 4 1,4125 A B C

PETCT3d30×3 4 1,4075 A B C

PETCT1p180 4 1,4050 A B C

PETCT2d180 4 1,4025 A B C

PETCT3l180 4 1,402 A B C

PETCT1d60 4 1,400 A B C

PETCT3l30 4 1,3850 A B C

PETCT3l60 4 1,3825 A B C

PETCT3p180 4 1,343 A B C

PETCT3p30 4 1,3275 A B C

PETCT1l30 4 1,3075 A B C

PETCT3d60×5 4 1,3050 A B C

PETCT3d30 4 1,3025 A B C

PETCT1p30 4 1,3000 A B C

PETCT1d60×3 4 1,2975 A B C

PETCT2d30 4 1,2950 A B C

PETCT3d60 4 1,2850 B C

PETCT1p60 4 1,250 B C

PETCT3d60×3 4 1,2450 B C

PETCT1l60 4 1,2325 B C

PETCT2l180 4 1,2250 B C

PETCT1d60×5 4 1,2150 B C

PETCT1d30×5 4 1,2075 B C

PETCT3p60 4 1,1975 B C

PETCT1d180 4 1,1975 B C

PETCT1l180 4 1,1900 B C

PETCT1d30×3 4 1,1850 B C

PETCT1d30 4 1,1600 B C

PETCRef 4 1,0800 C



the reference are marked in italic above.

100

Appendix VIII. TUKEY TEST: MAXIMUM AB-

SORPTION RATE FOR PETC Tukey Pairwise Comparisons



PETCT2l60 4 0,2900 A

PETCT3d30×3 4 0,2650 A B

PETCT1l60 4 0,2550 A B C

PETCT3d30×5 4 0,23000 A B C D

PETCT2d30 4 0,22750 A B C D

PETCT1l30 4 0,2275 A B C D

PETCT3l60 4 0,22500 A B C D

PETCT3d60×5 4 0,2225 A B C D

PETCT2d180 4 0,22250 A B C D

PETCT1d30 4 0,22250 A B C D

PETCT3d30 4 0,2200 A B C D

PETCT1d60 4 0,22000 A B C D

PETCT3l30 4 0,22000 A B C D

PETCT1d60×3 4 0,2200 A B C D

PETCT1l180 4 0,21750 A B C D

PETCT2l30 4 0,21750 A B C D

PETCT3d60×3 4 0,2175 A B C D

PETCT1d30×5 4 0,2175 A B C D

PETCT1d30×3 4 0,2175 A B C D

PETCT2d60 4 0,2150 A B C D E

PETCT2l180 4 0,2150 A B C D E

PETCT3l180 4 0,21000 A B C D E

PETCT3d60 4 0,21000 A B C D E

PETCT1d180 4 0,2050 A B C D E

PETCT2p60 4 0,2025 A B C D E

PETCT1d60×5 4 0,2025 A B C D E

PETCT3d180 4 0,19750 B C D E F

PETCT2p180 4 0,18750 B C D E F

PETCT3p60 4 0,18500 B C D E F

PETCT2p30 4 0,18000 B C D E F

PETCT3p180 4 0,16750 C D E F

PETCT3p30 4 0,1675 C D E F

PETCRef 4 0,1625 D E F

PETCT1p180 4 0,1550 D E F

PETCT1p60 4 0,1250 E F

PETCT1p30 4 0,11000 F



the Reference are marked in italic above.

101

Appendix IX. TUKEY TEST: DEMAND ABSOR-

BENCY CAPACITY FOR PETM Tukey Pairwise Comparisons



PETMRef 4 1,917 A

PETMT1p180 4 1,3325 B

PETMT1p30 4 1,3300 B C

PETMT1d30 4 1,2975 B C D

PETMT1d30×3 4 1,2875 B C D

PETMT1d30×5 4 1,2525 B C D E

PETMT1l180 4 1,2450 B C D E F

PETMT1d60×3 4 1,2175 B C D E F G

PETMT3d60 4 1,2150 B C D E F G

PETMT3d30×5 4 1,1900 B C D E F G H

PETMT1d60×5 4 1,1825 B C D E F G H

PETMT1l30 4 1,1825 B C D E F G H


PETMT3p60 4 1,1475 B C D E F G H

PETMT3d60×3 4 1,1400 B C D E F G H

PETMT3d30×3 4 1,1400 B C D E F G H

PETMT3p180 4 1,1375 B C D E F G H

PETMT3d60×5 4 1,1350 B C D E F G H

PETMT1d180 4 1,1300 B C D E F G H

PETMT3d180 4 1,1075 B C D E F G H

PETMT3d30 4 1,0925 B C D E F G H

PETMT3l180 4 1,0750 B C D E F G H




PETMT2p180 4 1,0375 C D E F G H

PETMT3l60 4 1,0350 D E F G H

PETMT1d60 4 1,0300 D E F G H

PETMT2p30 4 1,0275 D E F G H

PETMT3p30 4 1,0175 D E F G H

PETMT2d60 4 0,9800 E F G H

PETMT2d180 4 0,9725 E F G H

PETMT2d30 4 0,9625 E F G H

PETMT2l60 4 0,9525 F G H

PETMT1l60 4 0,9450 G H

PETMT2l180 4 0,9075 H



the reference are marked in bold italic above.

102

Appendix X. TUKEY TEST: MAXIMUM AB-

SORPTION RATE FOR PETM Tukey Pairwise Comparisons



PETMT1l30 4 0,62000 A

PETMT1l180 4 0,5400 A

PETMT1d180 4 0,475 A B

PETMRef 4 0,320 B C

PETMT3d30 4 0,300 B C

PETMT1d30 4 0,21750 C

PETMT1d30×3 4 0,21500 C

PETMT1d30×5 4 0,20500 C

PETMT1p30 4 0,20500 C

PETMT1d60×3 4 0,20250 C

PETMT1p180 4 0,20000 C

PETMT3l30 4 0,19750 C

PETMT3d180 4 0,19500 C

PETMT3d30×5 4 0,19250 C

PETMT3d30×3 4 0,19250 C

PETMT3d60 4 0,19000 C

PETMT3d60×3 4 0,18750 C

PETMT1d60 4 0,18750 C

PETMT3l180 4 0,1800 C

PETMT3d60×5 4 0,18000 C

PETMT3l60 4 0,18000 C

PETMT1p60 4 0,18000 C

PETMT2p60 4 0,17750 C

PETMT2d30 4 0,17500 C

PETMT2l30 4 0,1750 C

PETMT2d60 4 0,17500 C

PETMT2l60 4 0,17500 C

PETMT1d60×5 4 0,17500 C

PETMT3p180 4 0,17250 C

PETMT2d180 4 0,17000 C

PETMT3p30 4 0,16750 C

PETMT2p180 4 0,16750 C

PETMT1l60 4 0,16750 C

PETMT3p60 4 0,1675 C

PETMT2l180 4 0,1575 C

PETMT2p30 4 0,15500 C



the reference are marked in italic above.

103

Appendix XI. FTIR SPECTRA – PETC In this Appendix all FTIR spectra for PETC samples are shown. Each spectrum has

been normalised to the reference spectrum at peak 1409 cm-1

.

FIGURE 84 NORMALISED FTIR SPECTRA FOR PETC SAMPLES DYED IN 105°C FOR 30

MINUTES.


MINUTES.

0

0.1

0.2

0.3

0.4

0.5

01000200030004000

Ab

sorb

an

ce

Wavenumber [cm-1]

PETC Ref

PETC T1 p 30

PETC T1 l 30

PETC T1 d 30

PETC T1 d 30×3

PETC T1 d 30×5

0

0.1

0.2

0.3

0.4

0.5

01000200030004000

Ab

sorb

an

ce

Wavenumber [cm⁻¹]

PETC Ref

PETC T1 p 60

PETC T1 l 60

PETC T1 d 60

PETC T1 d 60×3

PETC T1 d 60×5

104


MINUTES.


MINUTES.

0

0.1

0.2

0.3

0.4

0.5

01000200030004000

Ab

sorb

an

ce

Wavenumber [cm-1]

PETC Ref

PETC T1 p 180

PETC T1 l 180

PETC T1 d 180

0

0.1

0.2

0.3

0.4

0.5

01000200030004000

Ab

sorb

an

ce

Wavenumber [cm-1]

PETC Ref

PETC T3 p 30

PETC T3 l 30

PETC T3 d 30

PETC T3 d 30×3

PETC T3 d 30×5

105


MINUTES.


MINUTES.

0

0.1

0.2

0.3

0.4

0.5

01000200030004000

Ab

srob

an

ce

Wavenumber [cm-1]

PETC Ref

PETC T3 p 60

PETC T3 l 60

PETC T3 d 60

PETC T3 d 60×3

PETC T3 d 60×5

0

0.1

0.2

0.3

0.4

0.5

01000200030004000

Ab

srob

an

ce

Wavenumber [cm-1]

PETC Ref

PETC T3 p 180

PETC T3 l 180

PETC T3 d 180

106

Appendix XII. FTIR SPECTRA – PETM In this Appendix all FTIR spectra for PETM samples are shown. Each spectrum has

been normalised to the reference spectrum at peak 1409 cm-1

.

FIGURE 90 NORMALISED FTIR SPECTRA FOR PETM SAMPLES DYED IN 105°C FOR 30

MINUTES.


MINUTES.

0

0.1

0.2

0.3

0.4

0.5

0.6

01000200030004000

Ab

sorb

an

ce

Wavenumber [cm-1]

PETM Ref

PETM T1 p 30

PETM T1 l 30

PETM T1 d 30

PETM T1 d 30×3

PETM T1 d 30×5

0

0.1

0.2

0.3

0.4

0.5

0.6

01000200030004000

Ab

sorb

an

ce

Wavenumber [cm-1]

PETM Ref

PETM T1 p 60

PETM T1 l 60

PETM T1 d 60

PETM T1 d 60×3

PETM T1 d 60×5

107


MINUTES.


MINUTES.

0

0.1

0.2

0.3

0.4

0.5

0.6

01000200030004000

Ab

sorb

an

ce

Wavenumber [cm-1]

PETM Ref

PETM T1 p 180

PETM T1 l 180

PETM T1 d 180

0

0.1

0.2

0.3

0.4

0.5

0.6

01000200030004000

Ab

sorb

an

ce

Wavenumber [cm-1]

PETM Ref

PETM T2 p 30

PETM T2 l 30

PETM T2 d 30

108


MINUTES.


MINUTES.

0

0.1

0.2

0.3

0.4

0.5

0.6

01000200030004000

Ab

sorb

an

ce

Wavenumber [cm-1]

PETM Ref

PETM T2 p 60

PETM T2 l 60

PETM T2 d 60

0

0.1

0.2

0.3

0.4

0.5

0.6

01000200030004000

Ab

sorb

an

ce

Wavenumber [cm-1]

PETM Ref

PETM T2 p 180

PETM T2 l 180

PETM T2 d 180

109


MINUTES.


MINUTES.

0

0.1

0.2

0.3

0.4

0.5

0.6

01000200030004000

Ab

sorb

an

ce

Wavenumber [cm-1]

PETM Ref

PETM T3 p 30

PETM T3 l 30

PETM T3 d 30

PETM T3 d 30×3

PETM T3 d 30×5

0

0.1

0.2

0.3

0.4

0.5

0.6

01000200030004000

Ab

sorb

an

ce

Wavenumber [cm-1]

PETM Ref

PETM T3 p 60

PETM T3 l 60

PETM T3 d 60

PETM T3 d 60×3

PETM T3 d 60×5

110


MINUTES.

0

0.1

0.2

0.3

0.4

0.5

0.6

01000200030004000

Ab

sorb

an

ce

Wavenumber [cm-1]

PETM Ref

PETM T3 p 180

PETM T3 l 180

PETM T3 d 180

111

Appendix XIII. CORRELATION ANALYSIS PETC In the tables below the results of correlation analyses for PETC are presented. The

significance level have been set to α = 0.05, meaning that p-values below or equal

to 0.05 indicate significant correlation.

The values in on cells are:

First value = suggested Pearson correlation coefficient

Second value = p-value determining the significance of the coefficient

TABLE 23 PEARSON CORRELATION COEFFICIENTS FOR RELATIONSHIPS BETWEEN MAXI-

MUM ABSORPTION RATE, DEMAND ABSORBENCY CAPACITY, AND DYED-VACUUM DRIED

PERCENTAGE WEIGHT DIFFERENCE FOR PETC SAMPLES. SIGNIFICANT RESULTS ARE

MARKED IN BOLD TEXT.

MAR DAC

DAC 0.134

0.435

Dyed-vacuum

dried weight

difference

-0.082

0.633

-0.416

0.012

TABLE 24 PEARSON CORRELATION COEFFICIENTS FOR RELATIONSHIPS BETWEEN DSC

RESULTS, TENSILE PROPERTIES, MOISTURE RELATED PROPERTIES, AND EXPOSURE TIME

ABOVE TG AND DYEING TEMPERATURE FOR PETC SAMPLES. SIGNIFICANT RESULTS ARE


∆Hc ∆Hm1 Breaking

strength

E-

modulus

Elongation

at break

DAC MAR

∆Hm1 0.383

0.021

Breaking

strength -0.666

0.000

-0.076

0.661

E-modulus -0.050

0.771

0.316

0.061

-0.005

0.978

Elongation at

break -0.407

0.014

-0.079

0.645 0.586

0.000

-0.145

0.400

DAC 0.252

0.138

-0.091

0.599 -0.526

0.001

0.119

0.491

-0.135

0.433

MAR 0.506

0.002

0.122

0.480 -0.403

0.015

0.134

0.438 -0.381

0.022

0.143

0.407

Time above

Tg 0.305

0.070

-0.162

0.344

-0.082

0.634

0.006

0.972

-0.170

0.323

0.028

0.871

0.160

0.351 Dyeing

temp. 0.328

0.050

-0.041

0.811

-0.191

0.265

0.130

0.451

0.152

0.377 0.444

0.007

0.275

0.105

112

TABLE 25 PEARSON CORRELATION COEFFICIENTS FOR RELATIONSHIPS BETWEEN ABSORB-

ANCE PEAKS SUGGESTED TO FORM TRANS-GAUCHE COUPLES, AND CORRELATION COEFFI-

CIENT BETWEEN ABSORBANCE PEAKS AND DSC RESULTS FOR PETC SAMPLES. SIGNIFI-

CANT RESULTS ARE MARKED IN BOLD TEXT.

A1339 A847 A898 A1371

A847 0.910

0.000

A898 0.761

0.000

0.923

0.000

A1371 0.429

0.009

0.496

0.002

0.378

0.023

∆Hc -0.177

0.303

0.029

0.865

0.246

0.148

0.166

0.333

∆Hm1 0.321

0.056 0.369

0.027

0.417

0.011

0.073

0.671

113

Appendix XIV. CORRELATION ANALYSIS PETM In the tables below the results of correlation analyses for PETC are presented. The

significance level have been set to α = 0.05, meaning that p-values below or equal

to 0.05 indicate significant correlation.

The values in on cells are:

First value = suggested Pearson correlation coefficient

Second value = p-value determining the significance of the coefficient

TABLE 26 PEARSON CORRELATION COEFFICIENTS FOR RELATIONSHIPS BETWEEN MAXI-

MUM ABSORPTION RATE, DEMAND ABSORBENCY CAPACITY, AND DYED-VACUUM DRIED

PERCENTAGE WEIGHT DIFFERENCE FOR PETM SAMPLES. NO SIGNIFICANT RESULTS

FOUND.

MAR DAC

DAC 0.311

0.065

Dyed-vacuum

dried weight

difference

0.046

0.789

0.188

0.273

TABLE 27 PEARSON CORRELATION COEFFICIENTS FOR RELATIONSHIPS BETWEEN DSC

RESULTS, TENSILE PROPERTIES, MOISTURE RELATED PROPERTIES, AND EXPOSURE TIME

ABOVE TG AND DYEING TEMPERATURE FOR PETM SAMPLES. SIGNIFICANT RESULTS ARE


∆Hc ∆Hm1 Breaking

strength

E-

modulus

Elongation

at break

DAC MAR

∆Hm1 0.332

0.048

Breaking

strength -0.173

0.312 0.502

0.002

E-modulus 0.221

0.195

0.277

0.102

0.114

0.508

Elongation at

break 0.012

0.944 0.642

0.000

0.562

0.000

0.075

0.666

DAC 0.044

0.798

-0.140

0.414

0.172

0.316

-0.133

0.439

-0.309

0.069

MAR -0.350

0.036

-0.142

0.407

0.276

0.103

-0.194

0.257

-0.216

0.206

0.305

0.071

Time above

Tg 0.304

0.071 -0.406

0.014

-0.584

0.000

0.105

0.544 -0.393

0.018

-0.063

0.716

-0.132

0.442 Dyeing

temp. 0.061

0.724

-0.173

0.313

-0.493

0.002

0.001

0.995

0.116

0.502 -0.736

0.000

-0.322

0.056

114

TABLE 28 PEARSON CORRELATION COEFFICIENTS FOR RELATIONSHIPS BETWEEN ABSORB-

ANCE PEAKS SUGGESTED TO FORM TRANS-GAUCHE COUPLES, AND CORRELATION COEFFI-

CIENT BETWEEN ABSORBANCE PEAKS AND DSC RESULTS FOR PETM SAMPLES. SIGNIFI-

CANT RESULTS ARE MARKED IN BOLD TEXT.

A1340 A847 A898 A1371

A847 -0.168

0.328

A898 -0.831

0.000

0.529

0.001

A1371 -0.637

0.000

0.778

0.000

0.814

0.000

∆Hc -0.376

0.024

0.397

0.017

0.474

0.003

0.520

0.001

∆Hm1 0.277

0.103

-0.168

0.327

-0.191

0.265

-0.239

0.160

Documents

hb.diva-portal.org1234438/FULLTEXT01.pdf · i ABSTRACT Polyethylene terephthalate (PET) is the most used fibre in the textile industry. PET is also used in other products, e.g. soft-drink