Frictional and mechanical properties of mercerized …nopr.niscair.res.in/bitstream/123456789/24646/1/IJFTR 29...Indian Journal of Fibre & Textile Research Vol. 29, September 2004,

Indian Journal of Fibre & Textile Research Vol. 29, September 2004, pp. 357-361

Frictional and mechanical properties of mercerized ring- and rotor-spun yarns

G K Tyagi", Ashvani Goyal & K Dhanda

The Technolog ical Institute of Textile & Scie nces, Bhiwani 127021 , India

Receii'ed 26 February 2003; revised received alld accepted 13 October 2003

The response o f cotto n ring- and ro tor-spun yarns to merceri zation treatment has been in vestigated. It is observed that the caustic mercerizatio n causes major changes in the mechanical and fri c ti onal behaviour of yarns, though the magnitudes of changes are different for different ring- and rotor-yarns, depending on the process parameters used. Both merceri zed ring and rotor yarn s d isplay higher knot and loop strength and lower extensibility, e lastic recovery and surface fricti on than the corresponding ullmercerized yarns. Merceri zation is an e ffective means of reducing hairiness and twi st li ve liness of both types of yarn.

Keywords: Cotton, Merceri za ti on, Ring-spun yarn , Rotor-spun yarn. Wrapper fibre, Yarn fri cti on

IPC Code: Int. C I. 7 DOIH 7/00, D06B 7/00, D06M 11100. GOI N 33/36

Various chemical treatments widely applied during the processing of cotton and polyester-cotton yarns and fabrics are very important because they alter the yarns and fabric s performance properties. Strong solutions of alkaline hydrates react with cellulosic fibrous materials such as cotton, linen, ramie and viscose rayon . The alkaline hydrates cause structural changes in the cellulose present in the secondary wall of cotton fibre, thus improvino the tensile strenoth b b ,

dyeability and lu sture ' . The efficiency of this treatment and the uniformity of product manufactured depend, to a large extent, on the geometry and structure of the yarns used . Though many studies2

-7 on

the response of colton ancl polyester-cotton OE rotor­spun yarns to mercerization have been performed with a view to modify their behaviour durin o weavin o and b b

post-chemical treatments, there seems to be a need for a dialogue on the role of mercerization in influencino

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the knittability of ring- and rotor-spun cotton yarns produced with varying twists and rotor speeds, because most of the earlier studies have put emphasis

"To whom all the correspondence should be addressed. Phone: 242561 ; Fax: +91-1664-243728; E- mail: [email protected]

on the selective tensile properties . The present paper reports the frictional and mechanical properties of cotton ring- and rotor-spun yarns as a consequence of mercerization treatment.

J-34 cotton (2.5 % span length, 24.3 mm; micronaire, 4 .2; and tenacity at 3 mm stelometer gauge, 19.8 g/tex) was processed on a Lakshmi Rieters' blow room line and carded on a MMC card . The carded sliver was given two passages on a Lakshmi Rieters' drawframe DO/2S to produce a finished sliver of 2.5 ktex. This sliver was spun into yarns (29 .5 and 59.0 tex) on Inglostadt rotor spinner RU lIIRU80 (4602) operated under normal mill conditions. The process parameters used to produce these yarns involved a 48 mm rotor operating at 833.33 and 1000 rps speeds, an opening roller speed of 100 rps and twist factors of 40.19,44.02, 47.85 and 51.67. To produce equivalent ring yarns, the drawn sliver was converted into a suitable rove of 1.5 hank on a Texmaco Howa Simplex and the rove was then fed to a Lakshmi Rieters' rin o frame G 511 usin o a b ;;:,

spindle speed of 12500 rps. Mercerization was can'ied out in a hank mercerization machine usin o 25% ;;:,

sodium hydroxide solution . After immersion for 120 s at room temperature, the skeins were stretched to 2% of their original length. The skeins were initiall y washed on the machine itself, neutralized with 2% sulphuric acid , thoroughly washed and then dried under atmospheric conditions.

All the yarns were tested for knot strength and loop strength on an Instron tensile tester (Model 44 11 ) according to BS: 1932 procedure. Yarn-to-metal friction was measured on the Shirley yarn fricti on recorder winder according to ASTM D 3 108 procedure. Yarn hairiness was recorded by Zweigles hairiness metre (Model G565). BSl test methodS was followed for measuring the snarling twist of ring- and rotor-spun yarns. Yarn elastic recovery was determined on a weighted ring yarn stiffness tester using the ring loop method9

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Table 1 shows the results of tensile tests. Invariably, mercerized ring- and rotor-spun yarns show substantially higher values of knot strength and loop strength than their unmercerized counterparts . The trend is consistent in all yarns, though the magnitudes of changes are different between ring- and rotor-spun yarns. Expectedly, the knot strength ratio

358 INDIAN J. FIBRE TEXT. RES., SEPTEMBER 2004

and loop strength ratio (Fi gs 1 and 2) of both unmerceri zed and merceri zed yarns are also signifi cantly higher than those of general knit wear yarns (0 .85). This sugges ts that the merceri zed ring and rotor yarns can survive severe bending and thus maintain their integrity during kni tt ing. For both knotted and looped specimens, breaking extensions of both ring and rotor yarns show a s igni ficant decrease after merceri zation. However, the loss in knot and loop breaking extensions of merceri zed rotor yarns at different twists reflec ts no specific trend . Although rotor speed has little effect on break ing exte nsion of unmerceri zed rotor yarns, there is a lesser decrease in breaking ex tension at higher rotor speeds due to the increased centrifugal force. Thi s ultimately makes the yarn more compact whi ch causes insuffic ient penetration of causti c liquor to ax ial fibres and consequently there is a decrease in the swelling of core fibres, resulting in lesser decrease in yarn breaking ex tension. T he hairiness resul ts (Fig. 3) show that the rotor-spun yarns are cons istently less hairy than ring-spun yarns. The hairiness tends to decrease as the tex twist fac to r increases . Higher rotor speed also produces fewer hairs due to the decrease in fri ction time of yarn between the coll ect ing groove and the ex it. The lesser fri ction time at higher rotor speed would entail a smaller number of hairs raised from the nucleous of the ya rn 10. Furthermore, regardless of yarn type, twi st factor and rotor speed, the merceri zed yarns have lesser hairiness than unmercerized yarns, as ex pected.

Yarn fricti on mainl y a ffec ts yarn tension in all tex tile processes including knitting. It is a lso the main cause of fluff shedding from the yarn during knitting. Higher yarn-to-metal f ri cti on damages the yarn structure and, therefore, the component fibres of the yarn are eas ily shed from the yarn body . Hence, the yarn fri ction with the needles during kn itt ing should be minimized to produce a low output tension. The mean values of yarn-to-metal fri c ti on are shown in Table 2. Invariably , the cotton rotor-spun yarns record signi ficantly lower surface fr iction than their ring­spun counterpart. When these yarns are merceri zed, the yarn-to-metal fri ction shows a reduci ng trend at all levels of twist. The reduction in yarn-to-metal fri ction ari ses due to the improved cross-secti onal shape and lay ing o f protruding fibres on the yarn surface, whi ch ultimately makes the yarn surface smooth and free from folds and creases I I . For both the yarn structures, the lower yarn-to-metal fri ction corresponds to the higher twist factors because a great

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1 Ring yarn (Grey) 2 Ring yarn (f'vIercerized) 3 Rotor yarn (Grey) , 833.33 rps

4 Rotor yarn (tv1ercerized), 833.33 rps 6 Rotor yarn (tv1ercerized), 1000 rps

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5 Rotor yarn (Grey), 1000 rps

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Tex tw ist factor

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Fig. I-Variation in knot strength rati o with tex twist factor [(a) 59.0 tex and (b) 29.5 textJ

1.6 1 Ring yarn (Grey) 2 Ring yarn (Mercerized) 3 Rotor yarn (Grey). 833.33 rps

4 Rotor yarn (Mercerized), 833.33 rps 5 Rotor yarn (Grey), 1000 rps (a)

1.2 6 Rotor yarn (Mercerized), 1000 rps

40 .19 44.02 47.85 51 .67

Tex twisl faclor

Fig.2- Variation in loop strength ratio with tex twi st factor [(a) 59.0 tex and (b) 29 .5 text)

359

360 INDI AN J. FIBRE T EXT. RES., SEPTEMB ER 2004

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120...-::----:=---:---=-- -------::----,---·--, RIng yarn (Grey) 2 R.ong yarn (Iv'Crccuzed) 3 Rotor yarn (Grey) 833.33 'ps (a) Rotor yarn (Pv'efcenl.cd) . 633 33 rps 6 Rotor yarn (Grey). 1000 rps

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amount of twist leads to less relat ive contact with the contiguous metal surface th an the low- twisted yarn. High rotor speed also tends to reduce yarn-to- metal fri ction. With increased yarn linear density, the yarn­to- metal fri ction shows an increasing trend due to greater proportional contact. T wist li veliness pl ays an important ro le in determining the perfo rmance of yarns during downstream processing. The results for snarling twi st o f cotton ring- and roto r-spun ya rns are g iven in Table 2 from wh ich it can be observed that the rotor-spun yarns have a lower tendency to snarl 12 .

For both ring-and rotor-spun ya rns, the snarling twist increases with the increase in tw ist factor, and at the same time when yarn linear density decreases. On the other hand , the snarling tendency of both types of yarn tends to reduce after merceri zation due to the relaxation of structural matrix of fib res in the yarn. Table 2 shows the ela tic recovery of cotton ring and rotor yarns as a consequence of merceri zat ion treatment. T he trend is consistent in all the yarns , though the magnitudes o f changes are di fferent between yarns. The decrease in elas ti c recovery of merceri zed yarns agrees wi th the common view that the mercerization reduces yarn breaking extension th rough permanent stretch by merceri zation tension. Further, the yarns spun with di fferent twist fac tors and rotor speeds respond di fferently to merceri zation treatment.

The increased producti on cost due to mcrcerization is expected to generate limited commercial interest, even though the merceri zation of cotton ring-and rotor-spun yarns with sodium hydroxi de offers

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SHORT COMMUNICATION 36 1

significant increase in knot strength and loop strength and decrease in elastic recovery and knot and loop breaking extensions. The level of change in these yarn characteristics is more marked in rotor yarns and it increases when both twist factor and rotor speed decrease, and at the same time when yarn linear density increases. Cotton rotor-spun yarns are consistently less hairy than the ring-spun yarns. The hairiness decreases with increasing rotor speed and twist factor, and there is a similar behaviour with the decrease in yarn linear density. Hairiness also gets reduced on mercerization . Cotton rotor yarns exhibit less twist liveliness than ring-spun yarns, which however increases with the increase in twist factor. Mercerization is an effective means of reducing the snarling propensity of both types of yarn. The frictional coefficient of cotton rotor-spun yarn is significantly lower than that of ring-spun yarn and it reduces with the increase in twist factor or decrease in yarn linear density .

References I Shenai V A, TechnoLogy of BLeaching and Mercerizing

(Sevak Publication, 306 Shri Hanuman Industrial Estate, Mumbai ), 1966,455.

2 Hari P K, Balasubramanian P, Sengupta A K & Chavan R B, Text Res J, 55 (1985) 122.

3 Bare ll a A & Manich A M, cited in Blended Textiles, edited by M L Gulrajani [The Textile Association (India), Bombay], 198 1,250.

4 Coarser H K & Turner A H, J Text Inst, 14 (1923) T 32. 5 Gupta 0 K, Kish M H & EI - Sieck A, Text Res J , 47 ( 1977)

428. 6 Pillay K P R & Nagaraja B S, Proceedings, 22"" Joint

TechnoLogicaL Conference (Ahmedabad Textile Industries Research Association, Ahmedabad), 1981, 21.

7 Tyagi G K, Kataria C B, Kaushik L N & Aggarwal V L, Illdian J Text Res, 14 (1989) 19.

8 Method of Test for TextiLes (British Standards Institution), 1974,3/31,3/36.

9 Owen 0 & Riding G, J Text Inst, 55 ( 1964) T 414. 10 Villa F, Rey A & Barella A, J Text blSt, 73 (1982) 55. II Hartsuch B E, Introduction to Chemistry (John Willey &

Sons, New York), 1950, 190. 12 Kl aeui H J, Knit Times, 43 ( 13) (1977) 55.