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Indian Journal of Fibre & Textile Research Vol. 21, March 1996, pp. 79~89
Recent advances in the development of silk-like polyester fabrics
Pushpa Bajaj
Department of Textile Technology, Indian In stitute of Technology, New Delhi 110016, India
Silk-like polyester fibres have been one of the most important targets for the textile industry in the present era. Key technologies starting from fibre engineering to finishing process have been illustrated for producing silky polyester fabric s with bulky hand touch and superior drape. Effects of polymer additives, delustrants, surfact a nt s, e tc. on a lkaline hydro lysis of polyester fabrics for improving silk-like characteristics have a lso been highl ighted.
Keywords: Alkaline hydrol ysis, Bicomponent fibres , Micro-crator polyes ter, Microfibrcs. Shingosen, Silk-like polyes ter. Spinning techno fogies
I Introduction Polyester fibre has conquered the leading position
among the three major synthetics because of its excellent properties such as high strength, abrasion resistance, wash and wear, and wrinkle-free characteristics. However, polyester does have some deficiencies, i.e. it is hydrophobic and oleophilic. Due to this, 1t is easily soiled and accumulates the static charge. Oily stains are also difficult to remove . Polyester fabrics are, therefore, not as comfortable as natural fibre fabrics.
by simulating the characteristic features of silk fibre , VIZ.
• The design of cross-sectional shape, • Enhancement of drape characteristics through
weight reduction of conventional polyes ter fibres or by the development offine denier fibres. and
On the basis of consumers' comments, Latta I has . also mentioned the following limitations of
synthetics:
• Creation of moderate bulk and soft handle. History of the progress made in silk-like pol yester
fibres is given in Table I and the technologies developed for the production of Shin-Go sen (Shin = new & Gosen = synthetic fibre) in Japan are illustrated in Fig.l .
In this review, the va rious processes developed for • Unnatural hand and unfamiliar skin cqntact
sensations, Table I- Histpry of the progress of silk-like polyester fibres9
• Unpleasant thermal sensations, • Lack of moisture absorbancy, • Clamminess of fabric in contact with skin, and • Static related problems.
Generation
Copy of natural silk ( 1964-)
To overcome some of these problems, blending Copy of silk touch
with natural fibres, particularly cotton, gained a big (1975-)
market. An extensive work related primarily to Persuit for the polyester fabrics comfort has been published in aesthetic
excellent reviews2 - 6 in the recent past. From the properties
wearer trials using knit fabrics it was reported that the (1979-)
comfort of polyester was substantially improved by Persuit for cross-section variations, pressure jet treatments and micro shape of
certain engineering modifications of the ·polyester. cross-section
The Japanese industry has also made great strides (1983-)
in improving the comfort and aesthetic properties of I S'lk I'k I "Sh' " h b Aim for high po yester. I - I e po yester mgosen as een sense and quality
developed by different technologies? Various (1988-)
approaches have been tried to develop silky polyester
Properties
Lustre Drape Rustle of clothes
Idea of technology
Brightness Shape of cross-section (trilobal, triangle)
Fullness and softness Shrinkage-mix fibres Drape Structure of crimps Delicacy
Silky-spun like Naturality Dry touch
Air texturing False twisting Thick and thin ya rns
Lustre Tri-petal like cross-Fullness and softness section Drape Microfibres Rustle of clothes Cross-sectional shape Naturality
Very nice ta ilored fini sh characteristics Liveliness
Development of new polymer
80 INDIAN J. FIBRE TEXT. RES., MARCH 1996
Shrinkag~-mix filam~nt ----i High shrinkage yarn High spQed spinning yarn Spontaneous extension
t---{ Difference in '"r---Fullness and fibre length softn~ss .
Polymer modification ------I Polymer with partic~s from catalyst residue Polym~r with added particles
Brightness )----.Lu~e
r:s-ur--:f:-a-ce-ro-u-g-:-hn-e-s .... s\.--L- Dee p co 10 ur
Special spinning -------1
Denier mix
Non-circul~r crosssection Conjugated yarn
He<lvy denier Fine dQnier
Texturing ----------1 False twisting Air tuturing
Afttr treatment -------1 After finish
Twisting (austic reduction Fabric density
Vi vid colour
Dry hand
I'---{ Shape of (ross - 'ff--- Soft hand section
Rustle of (Iothes
I-----{ Difference of 'c---\-- Spread anti-drap! denier
1----;rr;(o~m;;;m;;ii~ng~l;in;;;g-:-· -~~r\--~ Naturality dagree
l---'~S;;tr~u::-c t:t u:r:e--:o f;-""""":----+-~S t iff ness fabrics Springy properties
Drape
Fig. I- Fabric properties of Shingosen and key technologies
SI LOOK ROYAL 51 L~ SILK
I fI I 1 1\ ..... 1...-
\ I /
I" / '" -- I \../
" \V
1/ o 10 20 30 0 10 20 30 0 10 20 30
A-Sompl, 'tobric I B- '" ie rophont
Tim~Jms
fr-----o
c- W,ight , SOOt 14 em I 0-"'0_ '1Oem Imin I
Fig. 2- Wave of rustli ng sound of three typical fabrics
the production of silk-like polyester have been highlighted . Special emphasis has been made on the saponification or caustic reduction treatments for prod ucing si lk-like polyester fabrics .
2 Cross-sectional Shape 7 - <)
The shape of a silk fibre after removing sericine during scouring is triangular. For imitating the triangular shape of silk fibres, polyester fibres have
been developed with triangular or trilobal cross-sections. This resulted in lustrous polyester fibres. The appearance also changed from that of plastic to a silk equivalent.
PET fibres with a tripetal cross-section have also been developed to provide silky look . There is a groove at the tip of each lobe oftri lobal cross-section. This unique cross-section is believed to bring the rustling sound to polyester fabrics when friction occurs among them. The wave of rustling sound of three typical fabrics has been compared (Fig.2) . 'Sillook Royal' has, therefore, not only the lustre of natural silk, but also a rustling sound similar to that of the natural sil k.
Polyester fibres with petal-like cross-sections ha ve been produced by conjugate spinning technologylo. In this process, small amounts of easily hydrolysable components are located at the tips of each lobe. During saponification or caustic trea tment , this component gets dissolved and grooves a re formed. The width and depth of each groove can be controlled at the submicron level.
3 Differential Shrinkage Polyester Yarn One o f the technologies to bring out silk-like bulk
and handle in PET is to use differentia l shrinkage polyester component yarn. Two methods have been tried to produce different shrinkage levels in mixed
BAJAJ: SILK-LIKE POLYESTER FABRICS 81
yarns. One is a parallel sort of mixture, just like Quiana (nylon ya rn produced by Du Pont) and the other is a serial kind (Fig. 3).
The parallel structure is made by mixing fibres of different shrinkage levels either by using different polymer fibres or by mixing fibres of polyester drawn at different temperatures. The serial type is produced by random heat setting along individual fibres during fibre processing 1 I . The fibres shrink randomly with
TYPE PARALLEL SERIAL
Mi Xlld Yarn of Rnndom Hrat- set I'ETHOO D~rmt Shrinkage AmollJ Individual Fibre
Lt'it I
.. _ ................... .... . -
................ ... ......
YARN I--------:--+------:::---~ .~. '"'-./ .... ..../V ..... ~ ....... "'-." .... . ""'" ~ --v-..... J"'v ... _.
Parallel yarn str ucture
Strial yarn structure
Fig. 3- Two kinds of shrinkage. Parallel and serial ya rn structures
~I Double shrin k type
----, ..........
'-----
~ I ~~ ____ ~D_r_y_-_he_a_t_s_h_ri~nk~tY_p_e __ ~_~
Fig, 4
Grey 1st 2nd Final fabric hQat-set ntat-set heat-~t
scouring caustic dyeing reduction
Shrinkage d'iagram of polyest .r fab ric after caustic treatment
the heat treatment. In the parallel structure, higher shrinkage components form a core, and lower shrinkage components form waves or loops around the core. On the other hand , in the serial type structure, higher and lower shrinkage parts are di stributed randomy in the yarn and there is no core (Fig.3). The resulting fabric from serial type arrangement of different shrinkage level fibres showed a more natural silk look than the parallel type.
Uchida 12 has also demonstrated the role of shrinkage in producing Shingosen. Fukuhara 7 from Toray Industries has shown that for the production pf Shingosen, initially dry heat shrink process was tried and later the wet-heat shrink process. But, a double shr'unk fabric appears to be closest to silky textiles (Fig. 4). It has comparatively hi'gher bulkiness and is more airy and soft. Sillook Sildew, produced recently, is a double shrunk fabric with large waves or loops on the surface of the fabric.
For making double shrinkage fibres, the researchers have to first design the polymers by selecting a suitable comonomer and its content for accomplishing the desired shrinkage level. Degree of polymerization (DP) should also be controlled as a polymer with higher DP is likely to provide higher shrinkage.
After screening the polymer with a desired composition and DP, the fibres can be made from two
, or more polymer components by the same spinneret from different nozzles. This kind of conjugate spinning provides fibres with in situ differential shrinkage. So, additional step for mixing fibres as discussed earlier is not required and the resulting mixture directly produced from spinning line is uniform.
4 Topical Finishes Finishes also modify the tactile, static and moisture
related properties of polyester fabrics. The enhancement of polyester properties by treatment with aqueous sodium hydroxide was recognized soon after the invention of polyester 13 . Treatment of untextured yarn fabric with alkali produces softer tactility with a less synthetic hand . A calendar, heat-set' and caustic soda saponified fabric was patented a few.years later as the treatment was said to produce high fabric lusture without paper-like , handle l4
.
Polyester undergoes nucleophilic substitution and is hydrolyzed by aqueous sodium hydroxide . The hydroxyl ions attack the electron-deficient carbonyl carbons of the polyester to form an intermediate anion,
82 rNDiAN 1. FIBRE TEXT. RES., MARCH 1996
Table 2- Summary of alkalization processes
SI.No . Materials Formulations Conditions Remarks
Po lyester fa bric 0.3% NaOH in ethano l 50% pick up and Weight loss 2 1 % stored
2 Po lyes ter fabric 6% NaOH in 5% ethano l -do- -do-
3 Kodel IV drawn 5- 15% sodium hydroxide lOOT, I h Weight loss 12-43 % PET fibre & OH < t-butox ide hea t-set < sec. pro pox ide
< methoxide < ethoxide
4 Terene fibres 5- 15% aOH 900
e I h Weight loss 1. 5 in . sta ple length 12. 15-29.7 %
5 Trevi ra fabric Batch: 1.5-2 % NaOH I lOT, 20 min Weight loss 18% 90 g/m2 0.2% dispersing agent
H.T. beam: 0.05 % accelerator Pad-ba tch: 19% NaOH R.T. fo r 24 hr Silk-like fini sh
0.2% wetting agent batching More unce rtain Continuo us: 19% NaOH 1200 e I min 16-20% weight loss
0 .2% accelerator Silk-like handle
6 Textured P ET fi lament 15% NaOH Bath ratio 10:1 Weight loss, % l. 87 oz!ya rn 0.56 o r 0.87 % quaternary 30-60 min 17.5 Celenese Lauryl dimethyl benzyl 60 min 20.1 Fortrel 73 1 a moniull1 chloride 30 min 21 .9
60 min 24.4
7 Polyes ter 3% NaOH 95°C Weight loss 15°;.) Silk:like effec t
8 100% Dacron PET 10% aO H w e 120min Weight loss 10. 1 % fa bri c Strength loss 29'10
9 Light weight PET 4% aO H 90T. 60 min Weight loss 10.5-1 7.0% '68.5 g/m2 4% NaOH + I % accelera to r M:L: :1:60 Strength loss 25%
10 Po lyester WY., NaO H lOOT. 15 min Weight loss 13.74-14 . 11 %
I I Polyester crepe 10% NaOH IJOT Weight loss 100 g/m 2 n. 1 % s url~l c tant M:L::1: 30 21-23 % after 60 min
20% afte r 15 min Strength loss 10-70% warp
12 Pol yes ter Pad-ba tch WI. loss of tex t > flat > spun yarn
13 Po lyes ter Sodium triethylene glycolate (STEG» Weight loss Sodium d ie th ylene glycolate (SDEG) > STEG > SDEG > SEG Sodium ethylene gl yco late (SEG) Flex. rigidity
STEG < SDEG < SEG
14 Polyester textured yarn 3-5% NaOH 93-1 2 1°e Ih Weight loss 41 % Polyester textured fabric 5% NaOH 104T,. 1 h Weight loss 27 % Polyester 7. 5% Meth o no lic NaOH 2 1°C, I h Weight loss 26 .8%
15 Polyester yarn 10% NaOH 59T, 1-6 h Weight loss 18-25%
16 PET fibre , fabric 15% Hydrazin hydrade 30T Weight loss 23 % or ethylene diamine 70T 15% M:L: : I :20
17 PET & POY 10% NaOH 90T. I h Weight loss 20-80% fibres M:L:: I: 150
18 Heat-set delustred 2-8 mol NaOH 60T Weight loss PET fabric I % cet yl trimethyl 0-70 h 0-90%
ammonium bromide ( 1% w/w)
BAJAJ: SILK-LIKE POLYESTER FABRICS 83
Chain scission follows and results in the production of hydroxyl and carboxylate end-gro ups.
The effect of ca ustic solution on a PET fabric depends on the following parameters 15 - 19:
• Concentration of a lka li , • Time and temperature of alka li treatment, • Use of surfactants, • Fibre type (composition and cross-section),
and • Heat se tting. The fibre loses weight as the reaction occurs. Over a
wide range of temperature, the relation between weight loss and time or square root of residual weight and time has been found to be linear provided that a large exee ,; of alka li is used so that the reagent is not largely comumed during the treatment time. If an excess oT alkali is not used and its concentration decreases as the reaction continues, then the weight loss/time relation becomes exponential. Various conditions used for saponification and the weight reduction for polyester fabrics with aqueous sodium hydroxide are listed in Table 2. It has been concluded that the influence of temperature on the rate of the reaction is greater than that of concentration of alka li , which, in turn, is greater than that of time. Use of quaternary ammonium salts as accelerators for saponification has also been recommended6.20.2 1.
Samples hydrolyzed using 10% aqueous sodi um hyd roxide a t 60°C showed linear relationship between the weight loss and the alkali treatment time (Fig. 5). Further, the addition of a cationic surfactant, namely certrimmonium bromide (cetyl ammonium bromide) CTAM, or the replacement of PET with an anionically modified polyester (AMPET) increases the rate of saponification considerably. G awish and coworkers21 have shown that the rate of hydrolysis of polyester crqe fabric in \0 % NaOH (owl) at 130°C was vcry slow and it required six hours to the theoretical weight loss of 24%. However, with the addition of different quaternary ammonium surfactants as accelerators, the rate of hydrolysis co uld be enhanced significantly. The activity of the quaternary ammonium surfactants was in the following order:
Cetyl ethyl methacrylate dimethyl ammoni um bromide (CEMDA) > cetyl trimethyl ammonium bromide (CT AM) < oleyl bis-(2-hydroxylethyl)cetyl ammonium bromide.
Table 3- Properties of polyester samples sapon ified by pad-steam techniques
[Ca ust ic cone .. 150 giL; Steaming temp ., 102°C]
Sample Time of Weight Flexural Strength No . .steaming loss rigidity loss
(min) (%) (mg. em) (%)
I 24.77
2 5 12.3 11.99 7.3
3 10 15.7 9.28 15.8
4 15 18.6 8.39 17. 1
5 20 21.1 6.55 26.2
40r------------------------------,
~ o - 30 \II \II o ~ 20
Treatment Time (h)
Fig. 5- Rdationship between weight loss and treatment time for polyester fabric treated with aqueous caustic soda [( +) regular polyester, (0) regular polyester havi ng CTAM, ( x ) AMPET
subst ituted for regular polyester)
In presence ofCEMDA and CTAM, weight loss of 24% could be achieved on ly in 40 min at 130°C.
Correlation between weight loss, strength loss and flexural rigidity (Table 3) points out that the si lk-like soft handle of polyester can be realised 22 when the fabric loses a weight of about 16% and the flexural rigidity reduces to about 9 mg. cm by trea ting with 15% NaOH at 130°C.
End group analysis of saponified polyester indicates that with increasing weight loss of saponified polyester, the number of end groups of [COOH] increased and a value of 47.10 equivalents/106g was achieved at 2 1 % weight loss (Fig.6). The number for control being 32.8 equivalents/ I 06 g. The increased number of [COO H) end groups after the saponification suggests that the reaction of a lkali wi th polyester is of hydrolysis with scission of polyester chain molecules, resulting in more number of [COO H) end groups, and confirms the mechanism of hydrolysis as shown earlier.
The data on saponified polyester indicates that both the accumula ted charge (acceptance potential )
84 INDI A N 1. FIBRE TEXT. RES., MA RC H 1996
48 250
46
CII
44CDO 200
">" ;J CII
> ~150
42 "'. .. Cl. ;J o
c: ., o
Cl.
- e 40 '"
'0 c: ..
.. 100 38~ u c: E Cl. .. u
-< 50
24
I I
°0~------~----~12~----~18~----~~
I I Weig~t Loss (~o I 0. 29 0.31 0.33 0.35 0.37
Mo isture Regain, 'I,
0 0 W
L....J
36 ~ ci z
34
32
Fig. 6--Correlations between .weight loss. [COOH] end groups and acceptance potenti a l in saponified po lyes ter
and 11 /2 (the time fo r ha lf the accumulated charge to decay) reduce with increasing weight l oss~ The value of acceptance potentia l red uced from 200 V for control sample to 90 V for the saponified sample (25% weight loss) and the dissipation time 11 /2 reduced from 240 s to lOs. The data also show that up to about 13% weight loss the acceptance potentia l decreased rapidly to 11 5 V and with further increase in weight loss to 25%, it dropped slowly to 90 V (Ta ble 4). The reducti on in sta tic charge accumulati on of the alk ali-t rea ted polyes ter may be attributed to the surface saponi fica ti on of poly ester as indica ted by the inc reased nu mbe r of hydrophilic [COOH] and O H end groups, wick ing and , to a limited ex tent , the moisture rega in .
The effect of the ca ustic solution on a polyester fa bric depends a lso on the fi bre type, fa bric constructi on, and hea t-setting conditions. Bright fi bres with rou nd cross-section lose weight slowly than de lustred fib res with mult ilobal cross-section. Reaso ns fo r thi s di ffe rence in the rate of weight loss could be due to the fo llowi ng:
• For a given linea r density, a multil obal fib re wo uld have a large surface area than a round fi bre.
• The prese nce of de lustrant may accelerate the weight loss of the fib re23 . 24 .
Tahk 4 Eifeci ofs url;lce saponi fica tio n on elect ri c cond uct ivit : of po lyes ter sam ples
Sa mple Weight Accepta nce II 2
No. loss po ten tia l (5)
( % ) (V)
I 200 240
2 1.61 190 90
3 5. 24 160 30 4 13.5 1 11 5 2U 5 25 .1 4 90 10
Table 5- Fi nishing stages of polyes te r fibre fa brics15
Sa mple A Sa mple B
Loo m sta te
Relaxa ti on in washer ( I lOT. 20 min)
Hea t-se tti ng in hea tsett ing un it ( 190' C 20 s)
Weight reduction ( 16'Yo in 40 gi L NaO H )
Dye in g in jet dye ing machine (no'c. 30 min)
Raising
Loom SI a te
Relaxa tion in jet dye ing ( I l OT. 20 min)
Hea t-sett ing ( 190' C 205)
Weigh t red uction (25 % in 40 gi L NaOH )
Dyei ng in jet dyeing machine (130'C. 30 min )
Ra isi ng
• For peach like effect. high solubil ity polymers or inorga nic pa rticles are inco rpora ted in PET melt , which essenti ally solubilize or leach out to give pit effect on surface, thereby affecting the feel and hand le of the fa bric. Thi s radica l alterati on in the surface has been ensued by Japanese to prepare dry touch ya rn . Microcraters result in low convex-concave config urati on.
• Samples appea r to lose weight fas ter after texturing. For example, the losses in weight of non-tex tured ya rn and tex tured ya rn when treated with 5% caustic soda at 104°C for I h were 36% anri 41 % respectively.
Matsudaira and Matsui 25 have al so studied the effect of various fi nishing stages after the loom state on the fa bric handle. The di ffe rence between samples A and B is in the stage of relaxi ng and weight reducti on (Table 5). The effect of relaxing in a washer is expected to be greater than that in ajet dyeing machine. Overall , the polyes ter fi bre fa bric is remarkably softened and fa bric hand le by re laxa ti on, which includes desizi ng, ~h rin k i n g of fibres, and relaxing of in te rn al residual stress. Subseq uent weight reducti on d ue to alka li produces "efrecti ve gap" between the fi bres/or ya rn s and the splitting of fi bres. Tbe minimum amount of weight reducti on necessary to split fi bres is ex pected to be approx. 10%. By using discrimi na nt analysis
BAJAJ: SILK-LIKE POLYESTER FABRICS 85
with the primary hand values as variables, a distinctive zone for silk-like and peach-skin type polyester fabric can be found.
Sodium hydroxide treatment reduces electrostatic charge generation from 280 V to 100 V and the halflife from 5 to 2.5 s. Sol brig and Obendorf26 have reported the considerable weight loss after saponifying polyester fibre containi ng 2% Ti02 (Fig.7) and the pitting on the surface, obsefved through SEM, mainly axiall y oriented a long the fibre surface. Treating polyester fibre with 10% aq. NaOH at 100°C (by steaming) for 45 min produced hygroscopic polyester fibre.
In another study, a wide range of particles have been used for creating microvoids on the fibre surface. A common method is to remove microparticles blended in the polyester polymer by a lka li treatment. By applying this method to various polyester fibres containing differt'nt types of particles, fibres with various patterns of voids on surface are obtained. Originally, this modification was carried out to give depth of colour.
30
25 Dull Bright
~ 0 Serri().jll
- 20 Clear
'" '" .3 15 ..... ~
.~ 10 '" ~
5
OE-__ L-__ L-__ L-__ ~ __ ~ __ ~ ____ ~
Treatment Time
A method of forming a controlled microcrater on the fibre surface is proposed. The fibre pretreated by a ;pecific resist is exposed to a laser beam and then treated again with chemicals. This process can control the dimensions of voids such as depth , length and height, and their density.
A blend containing PET and 4% BaS04 (~ 2%, avo jiam. :::; 9 /-1m) was melt spun at 1800 m/min to give 290% elongation at Kuraray Co. The fibre wa~ used as sheath and later on textured by Taslan process and causticized to give 30% weight loss.
For improved lustre, polyester fibres containing :::; 0.04% inorganic oxide particles and having birefringence 0.03-0.08 were draw twisted for ~ 0.15 s at 130-170° and then untwi sted to give textured yarn with very good lustre 2 7 .
The effect of BaS04 on the extent of saponificat ion has a lso been studied in o ur laboratories28
. As the treatment time and concentration of NaOH progressively increased from I to 2 h and from 5 to 10% respectively, the loss in weight of the polyester fibre increased from 3.03% (Po, 5% NaOH , I h) to 15.2% (Po, 10% NaOH , 2 h) at 90°C bath temperature.
It can be seen from Table 6 that PoSi loses more weight over Po or P oSiF 5. This is perhaps due to the formation of sodium si licate in the presence of a lk ali. due to si licone oil coati ng on PET, which seems to acce lerate the sapon ificat ion process. The reduction in diam.is a lso maximum in PllSi fibres.
Fig. 7-Change in weight of clear. bright. semi-dull ai1d dull PET yarns over 6 h of treatment with \0% NaOH solution
After hydrolysis, elongated pits, o ri ented in the direction of the fibre ax is, on the surface of PllSi F " sample were noticed . However. unfilled fibres did not show any pits. It was found that the size of the pits depended on the length of expowre to alkali , while the number of pits depended on the concentration of BaS04 in the fibre (Fig.8). As the treatment time and a lk a li concentrat ion increased from I to 2 h and 5 to 10% respectively, the pits en larged mainly in the fibre axis direction. Longer treatment increased the size of the pits without changi ng their numbers. H ydro lyt ic
Table 6-Change in weight and diameter of BaSO.-filled polyester fibres after saponification
Sample 5% NaOH \0% NaOH
I h 2h I h 2 h
Wt loss Diameter Wt loss Diameter Wt loss Diameter Wt loss Diameter % ~m % ~m % ~m '1. ~m
Po 3.03 39.4 5.0 38.9 8.4 38.2 15.2 36.8
PoSi · 6.4 . 38.6 8.3 38 .3 13.4 37.22 22.2 35 .2
PoSiFs 4.{)5 39.1 5.52 38.8 10.5 37.94 18.8 36.04 Diameter of Po (unsaponified). 40 ~m; PoSi - si lane coated; PoSiFs - 5% BaS04-fi lled PET
Fig. 8- SEM of saponified BaSO"-fi lled PET [( a) No rm al PET, (b) PET fill eu wilh 5% B"SO", (e) PET tilled wilh to'Yt, B"SO", (d) Saponified norma l PET. (e) Saponified PET ti l led wi th SU!c, 8:ISO", alld (n Saponified PET fi l led with IO'y', 13aSO"1
00 0'1
z o ); z ;-
::!l 0:1
" tTl
rri >< :-i
fii y') !: » " (j :t
'" '" 0\
BAJAJ: SILK-LIKE POLYESTER FA BRICS 87
Table 7- Tensile properti es of sa ponified po lyeste r fibres
[NaOH conc .. 5%]
Sample code
Treatment time
I h 2 h
Tenacity Strength Brea king Modulus Tenacity Strength Breaking Modulus cN /tex r<: tenti on elongati on N ' tex eN/ tex retent ion elongation N/tex
% %
P" 38 96.5 2 1 10
P"Si 34 87. 1 IH 8.3
P"SiF, 36 97.0 18 11. 2
degrada ti on of the polyester begins a t the surface o f the fibre and continues until a BaS04 particle is exposed (Fig.8). Pits appear to develop from preferential hydrol ysis of polymer around the fill er particle, locations where alkali can diffuse more easily due to hyd rophilic nature of the fill er. Thi s action leaves an axially-oriented elli ptica l void around the filler particle, forming an entry point for the alkaline solution to attack polymer beneath the original surface. Possibly, the drawing process used in the production of fibres ca uses the pi ts to be ellip tical.
5 Tensi le Properties The tenacity, breaking elonga ti on and initial
modulus decrease wi th the increase in weight loss due to sa ponification (Table 7). Tensi le strength retention in Po fibres is 92% and 73.6% at 5% and 15.2% weight loss respectivel y. However, under the same conditions of treatment the percentage strength retention for P"SiF5 samples is slightly better, i.e. 94.8% and 75.4% at 5.5 % and 18.8% weight loss due to saponification .
The effect of silica particles on the lustre and handle of po lyester fibres after saponification has a lso been studied by Yamaguchi 29. The fine concave and convex structure is formed by a difference in solubility in a lk al i between the polyeste r and the particles uniformly dispe rsed in polyester. For making a fine concave and convex st ructure of a specific size, firstly ultrafine particles, which have a-similar refraction rate to fibrcs and an average di ameter below 100 nm. are uniforml y di spersed in polyester fibre wi thout cohesion. Silica has a tendency to cohesion by hydrogen bond of silica surface. So , silica in water is stabilized by Na + cation as silica solution. To prevent silica particles cohesion or agglomeration , silica sol is mixed with ethylene glycol and particles are stabilized and PET is made by direct estc rifica ti on method.
%
36.3 92.1
29 .5 75. 6
35. 1 94 .. 8
.5:.'/ '~ ': .. :,
POlyester..q;~t.". . :rf~(/"
.h J. • • .,ft:· .• ct> . { .. , . "'f ' f / - .. . l . .. , 'i"
:J!.t!Jzo Sil ica ~.i"'~
f R','N' $;Jji.~ ~("~ ~. Alkaline
treatment
ala
19
14
17
9.5
7.8
10.6
New surface
Fig. 9- Pieture of the fine concave a nd convex mechanism after alkaline treatment
Sol-dispe rsed silica as selected particles
P ro[)enics Silica Pol yester
So lubilit y rati o a gainst alkali 80
Index of refract ion 1.55 1.62
Oi <l me te r( pill) 0.05 10 ~ 10
The fibres containing silica are treated with an etchi ng method using alkali . Their surfaces are peeled ofr. Silica's solubili ty ratio against alkali is so rapid that a fin e concave and convex structure is formed (Fig.9).
Kurara y Company has dcveloped this fibre as the super microcrator polyester fibre '-' SN 2000" . Fig.1 0 shows the relation between fibre surface area (BET method) and alkaline weight reduction . The effect of microcrator due to alkali treatment on the depth of black colour has also been shown. So, at high alkaline weight reduction , polyester fibre of fine surface provides not only a deeper colour shade but an improvement in lustre and handle of the fabrics . Toray Industr ies30 prepared polyester fibres with mild silk-like luster by polycondensing glycol slu rries co ntainin g particles with (RI 1.3-2.0) and average
88 INDIAN J.FIBRE TEXT. RES., MARCH 1996 .
1.2 r--------- --------,15
'" -... . ~~-. --------r_ Micro-crater polyu.ter
E
-0 1.0 0 .c;
16
'" E
>-.... '" co '" OJ
17 c:
-'"
J. u d
co
d 0·8 ~
.q:
QI
u d
~
::> Vl
..&-._ ._ ._ . --0
..&. -..vt-----------r .-:: ...a.-r .............. __
Regular polyesf~r
Alkaline Weight Reduction (%)
Fig. I O-Relationships between the surface area, blackness and a lkaline weight reduction (Black dyed Georgette fabric)
primary particle diam.45 J.1m and average secondary particle ciiam.350 J.1m with polyacids to form PET, melt-spun and drawn to give trilobal fibres with silica content of 0.01-0.4% .
For rapidly hydrolyzable PET fibres , melt blending of PET with 2-10% sulfo containing aromatic diol(l) was carried out by Teijin Ltd3J .
H-t 0 C2H4)mO ----@{-OC C2H4 0 ~ H
S03 M ( I ) .
A woven fabric of the fibre showed weight reduction rate of 41 % /h in boiling aqueous NaOH. Ester Co. Ltd has developed polyester fibre with superior softness and gloss by dispersing 0.5-20% EPR in PET fibre. M~lt kneading was carried out and then spun into fibre32 •
Matsukawa et al. 33 have shown the recovery in tensile strength of alkali-treated polyester fabrics by subsequent treatment with chitosan (Table 8). The chitosan was fixed to the surface of saponified PET hy the reaction of the carboxyl groups .arid the amino groups of the chitosan molecu·les.
6 Weight Reduction by Amines1s
The reaction is similar to that by NaOH. The location of attack varies and depends on the mode of
Table 8- Moisture regain , st rength retention and the durability to washing of the chitosan-treated fabrics33
Fabric Add-on Moisture Strengt~ Durability to (%) regain retention washing
(%) (°lc,) (weight remained, % )
Untreated 0.4 100
Chitosan-treated 6.6 I.7 75.6 2.5 without curing 15.3 2.4 87.6 2.3
Chitosan-trea ted 6.4 1.6 138.0 95.0 with curing" 16.7 2.4 150.0 84.4
Alkali trea tment: 10% Sodium hydroxide, 90 min, 60' C Curing condition: 130' C, 90 min
application and the nature of amine. Amide formation results in chain scission. Amines were found to react and attack amorphous as well as crystalline regions. It appears, according to Zironian, that the weight loss/time curves are affected by the fine structure of the polymer and the location of attack.
7 Aftereffects o Deterioration in tensile properties o Broadens dye class for PET o Improved wettability o Oily soi l release improved o Good antistatic property o Increased moisture regain o Cracks developed on fibre surface o Brittleness increased o Flex life decreased o Shift in endothermic melting peak to lower
temperature o Improved pilling resistance.
References I Latta B M, Clothing com/ort: . Interaction of thermal.
ventilation . construction and assessment faClors (Ann Arbor Science, Ann Arbor, Michigan, USA), 1977, .33-35 .
2 Slator K , Text Prog . 9(4) (1977). 3 Yoon H N & Buckley A, Text Res l. 54 (1984) 289. 4 Yoon H, Sawyer LC& BuckleyA, Text Res l . 54(1984)357. 5 Zeronian S H & Collins M J, Text Chern C%r. 20(4) (1988)
25 . 6 Matsumoto M, Indian Text l . (Jan. 1991) 'J4 . 7 Fukuhara M, Text Res l . 63(7) (1993) 387. R Wada 0 , 1 Text Inst . R3 (1992) 322. 9 Sato M, Takakashi H, Sato Y, Sasaki H & Nabeshiwa K, Proc.
ISF'94 . (The Society of Fibre Science & Technology, Yokohama, Japan), 1994, 323.
10 lap Pat 62-53606; II November 1987. II lap Pat 51-30620; 2 September 1976. 12 Uchida A, Kakogijulsj. 25(4) (1990) 226. 13 Hall J D H, Ridge B P & DeMartino R N, US Pat 2,590,402
( 1952). 14 Gajjar N J , U S Pat 2,828,528; I April 1958.
BAJAJ: SILK-UKE POLYESTER FABRICS 89
15 Zeronian S H & Collins M J, Text Prog, 20(2) (1989) 70. 16 Houser K D, Text Chem Color. 15 (1983) 70. 17 Gawish S M & Ambrioise G , Am Dyest Rep, (Feb. 1986) 30. 18 Rane S S, Man-Made Text India, (July 1992) 251. 19 Ichida E, Uyama Y & Ikada Y, Text Res}, 61(8) (1991)4iD. 20 Yasutome K & Watanabe K, Jap Sen'e Kako , 33(2) (1981)
336. 21 Gawish S M, Bourgeois M & Ambrioise G , Am Dyest Rep,
(Dec. 1984) 37. 22 Rao A L N, Silk likefinish onpo/yestei and itsb/ends, M. Tech.
thesis, Indian Ins~itute of Technology, Delhi. 1986. 23 Solbrig C M, The alkaline hydrolysis of titimium dioxide
delustred PET, Masters thesis, Cornell University, 1986, 44-45.
24 Solbrig C M & Obendorf S K, Text Res J , 61 (1991) 177. 25 Matsudaira M & Matsui M, J Te'x t Inst , 83 (1992) 144.
26 Kuraray.£:"o .. Jap Po/ 07,90,736; C/refll Airs/I', 123 (1995) I I 5250g.
27 Toray Ind, Jap Pat 06,322.625; Chem Abstr , 122 (1995) 108592w.
28 Koul R, X-ray and (m/isra/ic polyester fibres, Ph . D thesis , Indian Institute of Technology, Delhi , 1994.
29 Yamaguchi S. Proc. ISF'94 , (The Society of Fibre Science & Tec/rnology , Yokohama , Japan) , 1994, 326.
30. Toray lrid .. Jap Pat 05.171,516; Chem Abstr, 1201(994) 56600j.
31 Teijin Ltd, Jap Pal 06.263.971; C/rern Abstr, 122 (1995) 190257x.
32 Nippon Ester Co. Ltd. Jap Pat 06,313,214; Chern Abs/r , 122 (1995) 1902601.
33 Matsukama S. Kasai M & Mizuta Y. Sen-i-Gakkaishi, 51 (I) (1995) 17.
