Indian Journal of Fibre & Textile Research Vol. 25, December 2000, pp. 246-250

A comparative study on quality of acrysorb and cotton terrysock fabrics produced from ring, rotor and dref-3 yarns

K R Sal hotra", P K Banerjee & R V M Gowda Department of Textile Technology, Indian Institute of Technology, New Delhi 1 1 0 0 1 6, India

Received 2 November 1 999; revised received alld accepted 22 Februw)' 2000

The superabsorbent acrylic fibre (acrysorb) was spun into ring, rotor and dref-3 yarns, which were knitted to terry sock fabrics. The quality of these fabric samples was evaluated and compared with that of terrysock fabric knitted from cotton ring yarn. The acrysorb yarns performed well in knitting, with the fabrics having better appearance and handle as compared to the cotton fabric. The acrysorb terrysock fabrics gave higher water absorption, water retention, drying capability and air permeabil ity than that of cotton fabric.

Keywords: Acrysorb, Cotton, Dref-3 yarn, Ring yarn, Rotor yarn, Tcrrysock

1 Introduction

Natural fibres such as cotton, si lk and wool offer wearing comfort because they have higher water absorbing capacity. However, owing to their stagnant production and higher cost, they are being overtaken by synthetic fibres which are relatively cheaper and more durable. On the other hand, the synthetic fibres are hydrophobic, prone to static generation and hence offer poor wear comfort properties.

Constant research efforts have been made by synthetic fibre manufacturers to impart moisture­absorbing properties to synthetic fibres. This has led to the development of superabsorbent fibres . The superabsorbent polymers I are crosslinked acidic polymers (usual ly of polyacrylic acid) in sodium salt form. Such materials absorb many times their own weight of aqueous fluid and retain it. The idea of superabsorbency has been introduced specially to acrylic fibres and they have been successfully produced by blending commercial polyacrylonitri le terpolymer with a wide range of incompatible polymers2. The incompatibil ity and phase separation is an important requisite for producing high water­retentive microporous fibres.

The superabsorbent acrylic fibres3 are reported to have good water absorbency, excel lent drying, warmth retention and air permeabi lity in comparison to cotton and other fibres. Ever since their

"To whom all the correspondence should be addressed. Phone: 659 1 402; Fax: 009 1 -0 1 1 - 6857757; E-mai l : kr_salhotra@hotmail.com

introduction into the market, the use of superabsorbent acrylics has grown rapidly, finding applications in baby diapers, inner garments, towels, handkerchiefs, sportswear, etc .

Acrysorb' i s a new superabsorbent acryl ic fibre produced by conjugate spinning of a terpolymer of acrylonitrile and a cellulose derivative2.

The present work was aimed at studying the quality and performance, especially absorbency, of terrysock fabrics made from superabsorbent acrylic fibre (acrysorb). For better understanding, it was compared with the quality of cotton tenysock fabric .

2 Materials and Methods

Superabsorbent acrylic (acrysorb) and cotton (1-34) fibres with specifications as shown in Table I were used.

2.1 Preparation of Yarn Samples

The acrysorb and cotton fibres were processed on a Laxmi Rieter 's b lowroom line and carded on a Laxmi Rieter's C 1 /2 card. The carded s l ivers were given two passages of drawing on a Laxmi Rieter' s drawframe DO/2S to produce finisher s l ivers of 2.55 ktex. Rovings of 1 . 1 hk were produced from these s l ivers and spun into yarns of 40 tex having tex twist factor of 3 1 .6 on a Textool ring frame.

Rotor and dref-3 yarns of the same count were directly spun from acrysorb drawn s l iver using the process parameters given in Table 2.

SALHOTRA el al. : ACRYSORB AND COTION TERRYSOCK FABRICS 247

Table I -Characteristics of acrysorb and cotton fibres

Characteristic Acrysorb Cotton

Length, mm 5 1 23 . 1 (mean) Fineness, dtex 1 .65 1 .46 Tenacity (single libre), cN/tex 24.2 Extension-at- break, % 35.5 Bundle strength, cNltex 24.3 Uniformity ratio, % 44.7 Density, glcc 1 . 1 9 1 .52

Table 2-Process parameters for rotor and dref-3 yarns

Rieter' s OE Dref-3 friction spinner spinner

Rotor diameter, : 55 Core-wrapper : 60:40 mm ratio

Rotor speed, rpm : 3 1 000 Spinning drum : 3700 speed, rpm

Opening roller : 7000 Opening roller : 1 2000 speed, rpm speed, rpm

Tex twist factor : 3 1 .6 Deli very rate, : 1 50 mlmin

Navel type : Smooth Friction ratio : 3.4

2.2 Yarn Testing

2.2.1 Tenacity and Breaking Extension

The yarns were tested on Instron for tenacity and extension-at-break with specimen gauge length of 500 mm and time-to-break of 20 ± 2 s.

2.2.2 Flexural Rigidity

The yarn samples were tested on the Shirley ring loop stiffness tester with the ring circumference of 7.75 cm.

2.2.3 Yarn-to-Metal Friction

The coefficient of friction between the metal and the yarn was determined on the Shirley yarn friction recorder. In this instrument, the yarn passes at a constant speed of 60 mlmin over an arc of a clean stainless steel disc. The coefficient of friction was obtained from the paper chart.

2.2.4 Twist

The yarns were tested on the twist tester with gauge length of 250 mm and tension 'f' [f= { 1 56/Count (Ne) } cN] . The detwist-retwist method was used for ring and rotor yarns, while the twist-to-break method was used for dref-3 yarn.

2.2.5 Diameter The diameter of yarns was measured on a

projection microscope (Projectina).

2.2.6 Unevenness and Imperfections The yarns were tested on the Uster tester at a speed

of 50 mlmin and sensitivity levels of +50%, -50% and +200% for thick places, thin places and neps respectively. For each sample, the yarn was run through the tester for 5 min.

2.2.7 Capillary Action The yarns were tested for capi llary action by

keeping the yarn vertical and dipping its lower end in water (slightly coloured for indication) in a beaker. The wicking height was recorded over time intervals of 1 , 2, 3 , 4 and 5 min.

2.3 Knitting of Terrysock Fabric A terry sock fabric4 basical ly consists of two yarns,

viz. the ground yarn and the pile yarn. The ground yarn is responsible for linear and areal dimensions and shape retention properties of the sock, while the loop-pile yam plays a significant role in deciding the degree of absorbency, drying and comfort properties.

In the present work, draw textured multifilament polyester yam of 1 55 den with 34 filaments was used for the ground structure, while the superabsorbent acrylic ring, rotor and dref-3 yarns along with cotton ring yarn were used for the loop-pile structure. The terrysock fabrics were produced on a circular tube knitting machine with the following details : Machine gauge, 3 .5 needles/cm; Diam. of machine, 1 00 mm; Total no. of needles, 1 10; Height of sinker, 3 mm; No.of feeders, 2; and Speed, 1 00 rpm.

2.4 Fabric Testing The fabric samples were scoured using the recipe

given in Table 3 .

2.4.1 Dimensional Characteristics of Fabrics The fabric samples were analyzed both in gray and

scoured states. The dimensional characteristics are given in Table 4 .

2.4.2 Surface Water Absorption The test was carried out on a typical water flow

tester as per the procedure described in D4772-88 ASTM Standards5 .

2.4.3 Water Retention There is no accepted standard test for water

retention of terry fabrics. However, the procedure

248 INDIAN J. FIBRE TEXT. RES. , DECEMBER 2000

Particular

Table 3-Scouring particulars

Acrysorb fabric

Cotton fabric

Material-to-Iiquor ratio Sodium hydroxide, g/I Sodium carbonate, gil Pine oil , gil

1 :20

30

1 :20 2

Lissapol - N (Detergent), gil Temperature, DC

5 70

5 Boiling

Time, min 1)0 60

Table 4-Dimensional characteristics of fabric samples

Characteristic

Wales/cm Courses/cm Stitches/cm2 Loop-pile/cm2

Stitch length, cm Ground yarn Pile yarn

Tightness factor

Areal density, g/m2

Thickness, mm

M/c state gray fabric 5 7 35 39

0.5 1 .2 1 3 .6

255

Scoured fabric

5 8 40 43

0.49 1 . 1 5 1 3 .9 (cotton); 14.0 (acrylic) 259 (cotton); 26 1 (acrylic)

3. 1 (RIC); 3.2 2.9 (RIC); 3. 1 (RIA); 3 .3 (ROA, (RIA, ROA, DRA) DRA)

RIC-Cotton ring fabric, RIA-Acrysorb ring fabric, ROA-Acrysorb rotor fabric, and DRA-Acrysorb dref-3 fabric

described in 046 1 -93 ASTM Standards5 has been used.

2.4.4 Drying Capability

The procedureJ for determination of drying capabi lity consisted of the following steps:

• cut a square specimen of 1 0 cm x 1 0 cm and weigh it,

• immerse the specimen in water for ample time and determine the amount of water (mg) absorbed,

• dry the sample for 30, 60, 90 and 1 20 min at an ambient temperature and determine the amount of water (mg) evaporated, and

• calculate the moisture releasing velocity per unit time (mg/min) which indicates the drying capability of the specimen.

2.4.5 Abrasion Resistance

The surface abrasion test was carried out on the Universal wear tester using the standard test procedure.

2.4.6 Air Permeability

The test was carried out on Shirley air permeabi lity apparatus using the standard procedure.

2.4.7 Compressional Resilience

The fabric samples were tested on Instron with cyclic compression and recovery. The test was carried out using the pressure varying from 0 to 50 g/cm2 at the rate of 5 mm/min compression. The thickness of the specimen compressed was plotted against the increasing and decreasing pressure and the compressional resilience (CR) was calculated as:

CR = Area under decreasing pressure curve x I 00 Area under increasing pressure curve

3 Results and Discussion

3.1 Yam Properties

3.1.1 Tenacity and Breaking Extension

Table 5 shows that the cotton ring yarn (RIC) has the highest tenacity and lowest extension. This can be attributed to the fol lowing facts:

(i) ring yarn is stronger than rotor and dref-3 yarns, (ii) tenacity of cotton is higher than that of

superabsorbent acrylic, and (iii) breaking extension of cotton is lower than that of

superabsorbent acrylic.

The lower tenacity values of acrysorb rotor yarn (ROA) and acrysorb dref-3 yarn (ORA) with respect to acrysorb ring yarn (RIA) is as per expectations. The ORA yarn is less extensible as compared to RIA and ROA yarns because of the fact that the straight and parallel core fibres in dref-3 yarn reach the breaking point earl ier than the helically arranged fibres in ring and rotor yarns.

3.1.2 Flexural Rigidity

Table 5 shows that the RIA, ROA and ORA yarns are s lightly stiffer than the RIC yarn as these are comparatively bulkier. For the same reason, ROA yarn is stiffer than RIA yarn . The flexural rigidity of ORA yarn is approximately two and a half times greater than that of RIA yarn. This can be attributed to the fact that in dref-3 yarn, the fibres in the core l ie paral lel to the yarn axis and tend to act as one unit, thus greatly restricting the relati ve movement of fibres. The higher flexural rigidity of dref-3 yarn may affect the loop formation and its shape in knitting.

SALHOTRA e/ al. : ACRYSORll AND COTTON TERRYSOCK FABRICS 249

3.1.3 Yarn-to-Metal Friction

It is observed from Table 5 that the coefficient of friction for RIC yarn is lower than that for other yarns. This is due to the natural wax in cotton acting as a lubricant. Further, unlike ring yarn with more smooth and regular surface, the rotor and dref-3 yarns have irregular surface due to wrapper fibre, which is also responsible for their higher friction. Hence, these yarns have to be waxed uniformly to reduce the friction before being knitted. 3.1.4 Twist

Table 5 shows lower value of twist in ROA yarn as against RIA yarn, which is due to the twist loss during yarn formation. The DRA yarn apparently has lowest twist realization, which could be attributed to slippage between the drum surface and yarn surface and l imitation of twist measurement of this yarn.

3.1.5 Diameter

It is clear from Table 5 that the RIA, ROA and ORA yarns have comparatively higher diameter than the RIC yarn. This is due to the fact that they are more bulky owing to the lower density of superabsorbent acrylic fibre. The ROA yarn has the highest diameter, followed by dref-3 and ring yarns. This can be attributed to more open surface stmcture of rotor yarn.

The relatively bigger diameter of acrysorb yarns often requires coarser gauge knitting machine in practice. 3.1.6 Unevenness and Imperfections

Table 5 shows that the RIC yarn has more imperfections than the three acrylic yarns. This can be

attributed to the presence of short fibres and trash in cotton. The ROA and DRA yarns have less number of neps as compared to RIA yarn due to further opening by the opening roller of the rotor and friction spinner. The ORA yarn appears to be more uneven than RIA and ROA yarns which can be due to the limitation of Oref-3 system in spinning counts beyond 1 4s Ne.

3.1.7 Capillary Action

Table 5 shows that the RIA, ROA and ORA yarns have h igher wicking heights as compared to RIC yarn. This clearly brings out the excellent capillary action of superabsorbent acrylic fibre.

3.2 Fabric Properties

3.2.1 Surface Water Absorption Table 6 shows that the RIA, ROA and ORA fabrics

have greater water absorption than RIC fabric. This clearly proves the greater absorbency of superabsorbent acryl ic fibre.

3.2.2 Water Retention

It is observed from Table 6 that the water retention of RIA, ROA and bRA fabrics i s higher as compared to that of RIC fabric. This represents superior moisture holding capacity of superabsorbent acrylic fibre.

3.2.3 Drying Capability

Table 6 shows that the RIA, ROA and ORA fabrics have significant difference in drying capability when compared to RIC fabric. This indicates easy removal of water from the pores of superabsorbent acrylic

Table 5-Properties of yarn samples

Property RIA ROA DRA RIC Tenacity, cN/tex 1 0.0( 1 2.3) 9.2(7.2) 7.6( 1 0.4) 1 2. 1 ( 1 3.4) Extension-at-break, % 20.0( 1 2.3) 20.3(7.3) 1 3 .2( 1 5.6) 6.6(9. 1 ) Flexural rigidity, mN-mm2 5.67( 1 5 .8) 6.92( 1 1 .8) 1 5 . 1 6( 1 3.7) 4.68( 1 7.5) Coefficient of friction

(yarn-metal) Unwaxedlwaxed 0.22/0. 1 8 0.23/0.20 0.25/0. 2 1 0.2 1 /0. 1 8

Twist, tpm 495(4.6) 426(2.6) 346(6.2) 500(5.3) Diameter, mm 0.29(4.3) 0.3 1 (3.G) 0.30(5. I ) 0.26(4.9) Thick places, thin places, 8, 45, 1 3 6, 4, 6 78, 1 1 3, 8 92, 1 8, 92

neps Uster CV% 1 7.7 1 2.9 20.7 1 8 .5 Wicking height (mm) at

60s 33 32 3 1 1 3 1 20s 4 1 42 40 1 6 1 80s 47 49 46 1 7 240s 52 54 50 1 8 300s 56 58 55 1 8

Values i n parentheses indicate CV%.

250 INDIAN J. FIBRE TEXT. RES., DECEMBER 2000

Table 6-Properties of fabrics

Property RIA Water absorption, mI 28.5( 1 4.2) Water retention. % 6 1 3 (484) Drying capability (ml) at

30 min 1 1 0 ( 1 1 2) 60 min 250 (248) 90 min 4 1 6 (4 1 3) 1 20 min 600 (597)

Abrasion resistance 428 (429) (number of rubs)

Air permeabi lity, cm3/s.cm2 74.6 (76.9) Compressional resi lience, % 48.2 (49.4)

Figures in parentheses indicate values for gray fabrics

fibre, unlike in cotton where the water is bonded through hydrogen bonds. There is no s ignificant difference in this respect amongst the RIA, ROA and DRA samples. The quicker drying capabi l ity of acrysorb is more useful when it is used in socks, towels, etc.

3.2.4 Abrasion Resistance

As seen from Table 6, the ROA fabric shows the highest abrasion res istance. This may be due to the greater diameter and presence of movable sheath fibre in the rotor yarn. There i s no significant difference amongst other samples. This shows that surface wear of acrysorb fabrics is as good as that of cotton fabrics .

3.2.5 Air Permeability

The acrylic fabrics show higher air permeabil ity than the cotton fabric (Table 6) . This could be attributed to the porous structure of superabsorbent acrylic fibre and yarn bulkiness. The ROA fabric is less air permeable as compared to RIA and DRA fabrics, because of the greater diameter of rotor yarn. The reduction in air permeabi lity of all the samples in their scoured state may be due to the increased stitch density .

The higher air permeabil ity of acrysorb fabrics would result in better wear comfort specially when used in socks.

3.2.6 Compressional Resilience

The lower compressional resilience value of RIC fabric represents its inferior resilience properties (Table 6) . The reduction in compressional resilience of fabrics in scoured state could be attributed to increased frictional restraint to recovery owing to the increase in stitch density.

ROA DRA RIC 29.5 ( 1 4.4) 28.0 ( 1 4. 1 ) 25.2 ( 1 0.3) 6 1 8 (486) 6 1 4 (483) 525 (367)

1 1 2 ( 1 1 4) 1 1 3 ( 1 1 4) 1 04 ( 1 02) 248 (255) 25 1 (254) 225 (223) 4 1 3 (4 1 4) 4 1 3 (4 1 4) 378 (373) 598 (602) 598 (559) 558 (559) 438 (440) 429 (427) 423 (425)

73.9 (75.8) 74.2 (76.5) 60.7 (62.8) 48.6 (50.5) 48.4 (50.0) 46.7 (48.5)

The relatively higher compressional resilience of acrysorb fabrics results in good cushioning effect and recovery from compression, specially when used as terry fabrics.

3.2.7 Subjective Handle Assessment

The scoured fabric samples were assessed by five judges for handle and ranked in decreasing order of handle as: RlA>ROA>DRA>RIC, indicating that the acrysorb fabrics have softer handle than cotton fabric.

4 Conclusions Acrysorb yarns exhibit better wicking behaviour

than the cotton yarn. Rotor yarn fabrics have the highest water absorption and abrasion resistance. Acrysorb terrysock fabrics have higher water absorption, quicker drying capabi l ity, higher air permeabi lity and soft handle than the cotton fabric . This indicates that the acrysorb is more suitable for manufacturing socks, towels and napkins.

Acknowledgement The authors are thankful to Mis Pasupati Acrylon

Ltd and to Prof. P Bajaj , lIT-Delhi , for providing acrysorb fibre. They are also thankful to Dr. S M Ishtiaque, Director, NITRA, and to Mis ALPS Industries, for providing facility to prepare rotor-spun yarn.

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( 1 997) 20. 2 Bajaj P & Dara M S, Indian J Fibre Text Res, 1 9 ( 1 994) 95. 3 Kenji Arai, J Text Mach Soc Japan, 30 ( 1 984) 72. 4 Anand S C & Lawton P J, J Text !lw, 78 ( 1 987) 326. 5 Annual Book of ASTM Standards, Section 7 (Textiles)

(American Society for Testing and Materials, Philadelphia), 1 996.