Effect of Fabric Structure and Degumming Conditions on the

Abstract—The current research studied the effect of

degumming conditions on the properties of PLA and silk yarns

aiming to get the actual influence of the process on each fiber

which would later be combined together into a blended fabric.

The degumming conditions with 10 g/l wetting agent were

employed at pH 5, 7 and 10 at various temperatures of 70, 80

and 90oC for 15 min. The most effective degumming was

recommended at 70oC and pH 10. Too high temperature (90

oC)

brought about an eroded fiber surface and deteriorated the

fabric strength. The PLA/silk blended fabrics were prepared

into different fabric structures and their properties i.e. strength,

density and stiffness, were investigated. The fabric properties

before and after degumming under a recommended conditions

were compared.

Index Terms—Poly (lactic acid), silk, blended fabric,

degumming.

I. INTRODUCTION

Nowadays an eco-friendliness of textile products becomes

a key interest not only in development of the textile industry

but also for product end-users who are conscious of

environment conservation and human safety regarding the

use of textile products. For this reason, natural fibers are still

popular in textile production. However, some important

textile properties cannot be provided by natural fibers e.g.

outstanding strength and easy-care properties, whereas

synthetic fiber can render those key properties satisfactorily

to the textile products. Therefore, synthetic fibers are still in

demand with seldom replacement being achieved.

Polyester fiber (poly (ethylene terephthalate), PET) is the

fiber with outstanding textile properties. It is from petroleum

resource, hence, it has been claimed to take part in global

warming problem, being the same as other petroleum-based

fibers. Recently, poly (lactic acid) or PLA, a greener

polyester fiber was developed and it was expected to replace

PET commodities. PLA fiber can be made by melt and

solution spinnings [1] but the former process is more popular.

It can be used in apparel and nonwoven applications for

textiles. It can be processed in the textile production but

milder processing conditions are employed for PLA as

Manuscript received October 14, 2012; revised January 2, 2013. This

work was supported by The National Innovation Agency (NIA), Thailand. A

partial funding was supported by Department of Textile Science, Faculty of

Agro-Industry, Kasetsart University, Thailand.

J. Suesat is with the Department of Textile Science, Faculty of

Agro-Industry, Kasetsart University, 50 Ngamwongwan Rd., Ladyao

Subdistrict, Chatuchak, Bangkok, 10900 Thailand (e-mail: Jantip.s@

ku.ac.th).

S. Ujjin is with the Kasetsart Agricultural and Agro-Industrial Product

Improvement Institute, Kasetsart University, 50 Ngamwongwan Rd.,

Ladyao Subdistrict, Chatuchak, Bangkok, 10900 Thailand (e-mail: aapsdu@

ku.ac.th).

compared with PET. Like PET, it can also be dyed with

disperse dye [2]-[4]. Nevertheless, it was reported that the

strength of PLA fiber was relatively inferior to that of PET

[5], [6]. Therefore, a further investigation focuses on

blending PLA with other textile fibers so as to improvement

the strength and also other essential properties [7].

Bombyx Mori silk is a cultivated silk composes of two

main compositions, i.e. sericin and fibroin. Silk fibroin is a

protein filament gluing together by sericin gum. Before

taking silk filament for exploitation in textiles, the silk

filament needs to be degummed in a hot alkaline soap

solution to remove sericin away. The degumming process,

thus, is the main pretreatment step for silk. Silk is a luxurious

fiber with quite high price compared with other common

textile fibers. Blending silk with PLA has been paid attention

because PLA is a biodegradable synthetic fiber derived from

plant and it is encouraging for green textile products where

PET should be replaced by the greener ones. Dyeing PLA and

silk yarns with natural dyes was investigated in our previous

work [8]. In this research, we aimed to study silk blending

with PLA fiber to create a new textile blended fabric. By

blending with the cheaper fiber, PLA, it would help to reduce

the cost in silk fabric production with new properties

generated. As PLA is rather sensitive to alkaline hydrolysis,

the effect of degumming process for silk was studied on both

PLA and silk at various conditions to investigate the optimum

degumming condition for PLA/silk blended fabric with

satisfactory degumming efficiency and less damage to the

fibers. The properties of the PLA and silk yarns after

degumming were examined. The PLA/silk blended fabrics

with various structures were studied their properties.

II. MATERIALS AND METHOD

A. Materials

The 40 Ne PLA yarn was purchased from Hebei Tianlun

Textile Co. Ltd, China. The 20-denier Bombyx Mori silk yarn

was obtained from Chul Thai Silk, Co. Ltd. Sera Wash, a

nonionic wetting agent, was supplied by DyStar, Co. Ltd.,

Thailand.

B. Effect of Degumming Conditions on PLA and Silk Yarns

The effect of degumming on the properties of silk and PLA

yarns was studied by treating the yarns in the solution

comprising 10 g/l Sera Wash (wetting agent) for 15 min at

various pHs of 5, 7 and 10. Degumming temperatures were

varied to 70, 80 and 90oC. The %weight loss of the yarns was

determined from the weight of the yarn after degumming

comparing with the initial yarn weight. Tensile strength of

the degummed PLA and silk yarns was measured by

Shimadzu Autograph AGS-J series with the gauge length of

Effect of Fabric Structure and Degumming Conditions on

the Properties of PLA/Silk Blend

Jantip Suesat and Suchada Ujjin

International Journal of Bioscience, Biochemistry and Bioinformatics, Vol. 3, No. 2, March 2013

106

60 mm and crosshead speed of 300 mm/min. The whiteness

of the degummed yarns was assessed by McBeth ColorEye

7000 spectrophotometer. The surface morphology of the

degummed yarns was collected by JEOL JSM-5800 LV

scanning electron microscope (SEM).

C. Preparation of the Woven Fabrics Containing PLA and

Silk Yarns with Different Fabric Structures

The woven fabrics containing PLA and silk yarns in the

structure were prepared. The detail of each structure is

depicted in Table I. The 20/3 denier silk yarn was used as a

warp for all fabrics. The structures 1-4 are the PLA/Silk blend

with different weft PLA yarns, viz. 40/2, 40/3, 40/4, 40/5Ne,

meaning that the 40Ne PLA yarns are plied together

according to the number after / symbol while those of 5-6 are

the 100% silk fabrics but different in silk yarn structure,

being used as a weft. The fabrics were prepared by means of

rapier power loom. All the fabrics was taken to measure their

propertied, viz. density (weight/unit area), strength and

stiffness. The strength of the fabrics was obtained from

Shimadzu Autograph AGS-J series. The fabric stiffness was

indicated in terms of flexural rigidity. By measuring the

bending length of the fabrics along the weft direction

according to BS 3356 standard test method, the flexural

rigidity could be calculated.

TABLE I: STRUCTURES OF PLA/SILK BLENDED FABRICS

Fabric

parameters

Fabric structure

PLA/Silk Silk

1 2 3 4 5 5

1 Warp-Silk

yarn (denier)

20/3 20/3 20/3 20/3 20/3 20/3

2 Weft-PLA

yarn (Ne)

40/2 40/3 40/4 40/5 - -

3 Weft-silk yarn

(Denier)

- - - - 20/6 20/10

4 PLA:silk ratio 3.80:1 3.98:1 5.06:1 5.32:1 - -

5 Fabric density

(g/m2)

101.4 121.1 140.9 235.5 83.93 98.72

6 Warps/inch 99 103 103 103 99 99

7 Wefts/inch 66 57 47 42 78.6 75

D. Effect of Degumming Conditions on the Properties of

PLA/Silk Blended Fabrics

The prepared fabrics with different structures were taken

to study the influence of degumming on their properties. The

effect of degumming condition was investigated by treating

the fabrics in a bath containing 10 g/l Sera Wash (wetting

agent) at pH 10 and liquor ratio of 20:1. Degumming was

performed at 70oC for 15 min. The degummed fabrics were

left to dry at room temperature and then their properties, viz.

density, strength and stiffness, were measured.

III. RESULTS AND DISCUSSION

A. Effect of Degumming Conditions on PLA and Silk

Yarns

The properties of PLA and silk yarns after being

degummed at different conditions are demonstrated in Table

I. The whiteness of silk yarns increased considerably when it

was degummed at pH 10. This was in accompanying with the

loss of fabric weight and reduced strength when compared

with those at pH 5 and 7. No weight and strength losses were

noticed when degummed the yarns at pH 5 and 7. This result

points out that degumming silk at pH 10 gives a high

whiteness but impairs the yarn strength. For PLA, it is a

manmade fiber, so the degree of whiteness is much higher

than the silk yarn. The whiteness of the yarn increased

slightly when the pH of degumming process increased from 5

to 7 and 10. No signified effect was observed when varied the

degumming temperatures. The extent of weight loss did not

changed significantly except that at 90oC and pH 10, about

twofold of yarn weight was lost as compared with the 80oC

counterpart. This weight loss result was correspondent to the

strength reduction of PLA at 80-90oC and pH 10. It was

reported that PLA could be damaged in a hot alkaline

solution [9-10]. Alkaline hydrolysis takes place and the

damage on PLA fiber is claimed to be surface erosion where

the hydrolysis causes a gradual erosion of the fiber surface

and fiber then becomes thinner [10]. This brings about a

reduction in weight and strength of PLA fiber. When

compared between the influence on silk and PLA, it can be

seen that the effective degumming can be achieved for PLA

and silk at 70oC and pH 10 with a whiteness improvement

and less strength loss. This result elucidates that the optimum

degumming condition of 70oC at pH 10 for 15 min could be

practically viable for PLA/silk blended fabric.

TABLE II: PROPERTIES OF PLA AND SILK YARNS AFTER BEING DEGUMMED UNDER DIFFERENT CONDITIONS

Degumming conditions Silk PLA

pH Temp Weight loss

(%) Whiteness

Strength

(N/denier)

Weight loss

(%) Whiteness

Strength x10-3

(N/denier)

control 0 34.22 0.043 0 55.23 9.4

5 70 0 34.23 0.043 0.40 58.02 9.2

5 80 0 34.73 0.041 0.28 63.07 9.1

5 90 0 34.91 0.040 0.14 64.34 9.2

7 70 0 34.59 0.043 0.38 64.56 9.4

7 80 0 36.23 0.041 0.33 63.99 9.9

7 90 0 38.60 0.045 0.14 62.44 9.9

10 70 17.51 55.63 0.038 0.64 63.19 1.03

10 80 19.08 56.20 0.038 0.68 63.41 8.7

10 90 19.19 55.79 0.036 1.20 62.82 8.6


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70oC 80oC 90oC

pH 7

70oC 80oC 90oC

pH 10

Fig. 1. SEM photographs of PLA yarns degummed under pH 7 and 10 conditions at 70, 80 and 90oC

The SEM photographs of PLA yarn degummed at pH 7

and 10 at varying temperatures are shown in Fig. 1. Phillips et

al. [9-10] reported that PLA could undergo a serious bulk

erosion even under neutral pH but from our result in Table 1,

there was no strength loss observed for degumming at pH 7,

the SEM photographs also showed no change in fiber surface

morphology. In the meantime, degumming in alkaline

conditions at 90oC caused a damage to the surface of PLA

fiber. Some crack marks and erosion could be noticed. This

SEM results corresponded to the strength reduction

mentioned before. Erosion of fiber surface makes the fiber

become thinner and subsequently, weaker. A less damage

was found for 80oC but a slight surface erosion could be seen.

It also confirms that degumming process at pH 10 at 80-90oC

is too vigorous for PLA/silk blended fabric as it could harm

PLA.

B. Effect of Degumming Conditions on the Properties of

PLA/Silk Blended Fabrics

The results in the previous section have told that

degumming process for PLA/silk blended fabric should be

done using 10 g/l wetting agent at pH 10 and temperature of

70oC. This recommended degumming condition was used for

PLA/silk blended fabrics in this section. Table III shows the

properties of PLA/silk blended fabrics. Each no. of fabric

structure contained different PLA and silk composition and

structures. The fabrics no. 1-4 were the PLA/silk blend with

20/3 denier silk yarn as a warp and PLA yarn as a weft but

with different number of yarns plying together. The fabrics

no. 5-6 were 100% silk fabrics with different weft structures.

The density of each fabric marginally increased after

degumming due to fabric shrinkage resulting in a more

compact structure, the weight/unit area of the fabric was then

increased. A denser fabric structure brought about a stiffer

fabric. The flexural rigidity of each fabric increased after they

were degummed. The strength of the fabrics was also

increased after degumming as seen from the increment of

maximum tensile load applied in fabric strength testing. With

the same warp yarn, higher number of weft yarns plying

together imparted higher density, stiffness and strength to the

fabric both before and after degumming. This provides the

information that different fabric properties can be

manipulated by the fabric structure in order to gain a wide

variety of fabric textures and properties. This is anticipated

for the development of PLA/silk blended fabric to serve the

home textiles industry e.g. bedding, where luxurious silk

fabric is typically major products. PLA, a cheaper fiber, can

also do its function in the blend and also help to reduce cost

of the production.

TABLE III: PROPERTIES OF PLA AND SILK YARNS AFTER BEING DEGUMMED AT DIFFERENT CONDITIONS

No. Warp Weft PLA / Silk

ratio

Density (x10-2g/cm2) Tensile max load (N) Flexural rigidity

(x10-2 g.cm)

Pre degum. After

degum. Pre degum.

After

degum. Pre degum.

After

degum.

1. Silk 20/3 D PLA 40/2Ne 3.8 : 1 1.01 1.08 156.33 183.71 1.93 1.46

2. PLA 40/3Ne 3.98 :1 1.23 1.31 167.86 195.06 5.06 2.58

3. PLA 40/4Ne 5.06 :1 1.33 1.52 161.07 195.39 5.96 3.82

4. PLA 40/5Ne 5.32 : 1 1.43 1.51 161.40 199.00 8.36 4.50

5. Silk 20/3 D Silk 20/6 D - 0.69 0.91 224.95 250.24 2.72 5.76

6. Silk 20/10 D - 0.98 1.07 329.58 331.89 7.03 7.86

IV. CONCLUSION

From this research, it gives the idea that blending silk with

PLA could be technically viable. PLA, an alkali sensitive

fiber especially at elevated temperature, can tolerate the

alkaline degumming conditions need for silk pretreatment to


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remove sericin. The optimum degumming conditions are

recommended not to perform at the temperature as high as

90oC for the condition studied as hydrolysis reaction would

reduce PLA strength. Practical coloration of PLA/silk blend

can also be done industrially with a proper choice of

dyestuffs and processes. It is encouraging to develop this

PLA/silk blended fabric for producing green alternative

products with lower price as compared with the expensive

100% silk fabric.

REFERENCES

[1] B. Gupta, N. Revagade, and J. Hilborn. “Poly (lactic acid) fiber,” An

Overview, Progress in Polymer Science, vol. 32, pp. 455-482, 2007.

[2] J. Lunt and J. Bone, “Properties and Dyeability of fibers and fabrics

produced from polylactide (PLA) polymers,” AATCC Review, pp.

20-23, 2001.

[3] J. Suesat, T. Mungmeechai, P. Suwanruji, W. Parasuk, J. A. Taylor,

and D. A. S. Phillips. “Correlation between the shade of an azo disperse

dye on poly (ethylene terephthalate) and poly (lactic acid) fibres with

its spectroscopic properties in selected organicsolvents,” Coloration

Technology, vol. 127, pp. 217-222, 2011.

[4] J. Choi and W. Seo, “Coloration of poly (lactic acid) with Disperse

dyes. 1. Comparison to poly (ethylene terephthalate) of dyeability,

shade and fastness,” Fibers and Polymers, vol. 7, no. 3, pp. 270-275,

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[5] J. Suesat, D. Phillips, M. Wilding, and D. Farrington. “The influence of

yarn-processing parameters on the tensile properties and structure of

poly (l-lactic acid) fibres,” Polymer, vol. 44, no. 19, pp. 5993-6002,

2003.

[6] J. Suesat and P. Suwanruji. “Dyeing and fastness properties of poly

(lactic acid) fiber,” in Textile Dyeing, P. J. Hauser, InTech Publishing,

ch 16, 2011.

[7] J. Suesat, P. S. Be, and P. Suwanruji. “Effect of pretreatment and

dyeing processes on the physical properties of poly (lactic acid)/cotton

blended fabric,” Advanced Material Research, vol. 486, pp. 253-259,

2012.

[8] S. Ujjin and J. Suesat. “Study on the dyeing properties of poly (lactic

acid) and silk yarns with natural dyes,” Advanced Material Research,

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Sawyer, J. Bone, and S. Dervan, “Influence of different preparation and

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Jantip Suesat was born on 29th November, 1976 in

Thailand. She was graduated from University of

Manchester, Manchester, U.K. for her Ph.D. in

Textiles in 2004. After graduation, she started her

work as a LECTURER in textile science and

technology at Department of Textile Science, Faculty

of Agro-Industry, Kasetsart University, Thailand until

present. Her research interests are in the field of textile

chemical processing, i.e. pretreatment, dyeing, printing and finishing of

textiles. She has been intensively researching about poly (lactic acid), PLA,

fiber since her Ph.D. study at University of Manchester and still continues

the research work in this area up till now and has generated a number of

publications regarding PLA fiber. Her current researches concerns the

development of disperse dyeing of polyester, textile chemical finishing and

utilization of natural dye for textiles.

Suchada Ujjin is currently a SENIOR

RESEARCHER at the Kasetsart Agricultural and

Agro-Industrial Product Improvement Institute

(KAPI). She was graduated for her Master degree in

Plant Pathology from Kasetsart University in year

1980. She focuses her research interest in dyeing

textiles with synthetic and natural dyes. Development

of textile from silk is also her field of expertise. Along

with doing a research, she has also been working closely with the rural

communities where silk sericulture are located in terms of training and

development of local team to help strengthen local silk production

communities in Thailand. Her current research regards the development of

silk products, blending of silk with other textile fiber and natural dyes.


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Documents

Effect of Fabric Structure and Degumming Conditions on the