Indian Journal of Fibre & Textile Research Vol.23, March1998, pp. 8-12

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Studies on the properties of dref-spun acrylic yams

A Chaudhuri InstituteofJuteTechnology,35 BallygungeCircularRoad,Calcutta700 019, India and G Basu NationalInstituteof ResearchonJuteandAlliedFibreTechnology,12 RegentPark,Calcutta700 040, India

Received22 May 1996; revisedreceived9 May 1997; accepted10 June 1997

The properties of dref-spun acrylic yarns having polyester, nylon and polypropylene multifilament yarns as core and of 100% acrylic yarn without core have been studied. It is observed that the tenacity and work of rupture of core-spun acrylic yarns are higher than that of 100 % acrylic yarn, whereas the breaking elongation of all the yarns is more or less same. Nylon core yarn apparently exhibits slippage between sheath fibres and core during the application of tensile load. Packing coefficient values indicate that the structures of core - spun acrylic yarns are less compact than that of acrylic yarn. Introduction of core filament improves the regularity of friction - spun yarns.

Keywords: Acrylic yarn, Dref spinning, Flexural rigidity, Multifilament yarn, Nylon, Packing coefficient, Polyester, Polypropylene, Tenacity

1 Introduction properties of dref-3 spun multi component Since its advent the friction spinning has polyester (Trevira) yarns where Trevira i attracted, to a great extent, the textile engineers multifilament and monofilament yams were used due to its very high delivery speed and soft as core. They observed that monofilament does not handling of the yarn. The friction-spun yarns are serve any purpose for improving the strength of the bulkierl than the ring- and rotor-spun yarns and the yarn. system is suitable for spinning of coarse yarns. The friction-spun yarns are very useful for terry towels, A disadvantage of the core yarns is that the weft yarns, pile yams, stuffer yarns, blankets, staple fibre sheath may slip along the filament core furnishings and technical textiles. The properties when being pulled to pass over or rubbed by of friction-spun yarn, ring-spun yarn and yarns machine parts during further mechanical spun on other systems have been compared by processing. Miao et ai.5 studied, the influence of ~.. some workersl.2. Louis et al.' observed that spinning parameters on core yarn, sheath slippage friction-spun yarns are weakest when compared and other properties. They observed that in case of with ring, rotor and dref-3 spun cotton yarns. dref-2 spun core yarn, a low filament pretension is Brockman2 found maximum strength in wrap preferable for spinning core yarn with good sheath spinning followed by ring, air-jet, rotor and slipping resistance. Twisting the filament before friction spinning respectively for 20s Ne yarn core yarn spinning also significantly affects the made from 65:35 polyester-cotton blend. Mass sheath slipping resistance. To increase sheath irregularity of friction-spun yarn is higher than slipping resistance, the filament pre-twist should those of spun on other spinning systems. Further, be in the same direction as the sheath twist. the friction-spun yarns are more hairy than all However, not much work has been reported in the other yarns 1-3. Padmanabhan and Ramakrishnan3 literature on the influence of properties of filament observed that the filament core dref -3 spun yarn is core on the properties of core-spun dref yarn. A stronger than 100% cotton yarn and cotton-core detailed study in this direction has become yarn. Gebauer and Schlossarek4 reported the essential for maximum commercial exploitation of

" I I" I III Illilll CHAUDHURI & BASU: DREF-SPUN ACRYLIC YARNS 9

potentialities for specific use of the engineered machine. yams. 2.2.2 Evaluation of Tensile Properties The present work was aimed at evaluating the Zwick universal tensile tester was used to various properties of dref-spun 100% acrylic yam evaluate the tensile properties. Breaking load and as well as core-spun acrylic yams. The efforts have breaking extension of multifilament yams and dref been made to assess the influence of core filament yams were measured at 300 mmlmin cross-head characteristics on the physical properties of core• speed with 500 mm gauge length. The average of spun dref-2 yam. Polyester, nylon 6 and 50 test results was taken for each sample. polypropylene multifilament yams were used as For evaluation of stress-relaxation, the yam was core and acrylic staple fibre as sheath material. stretched up to 1% extension and allowed to relax for 5 min at the same condition. The percentage of 2 Materials and Methods force decay was calculated by the following 2.1 Materials formula: Acrylic staple fibre (1.5 denier, 51 mm length) (l -1) Stress relaxation (%) = 0 t X 100 top of25.2 cN/tex average single fibre strength and 10

28% average elongation was used as sheath where 10 is the initial load on yam at 1% material. extension; and It , the load on yam at 1% extension Polyester (90 dtex,32 filaments), nylon 6 (80 at time t (5 min.). dtex, 24 filaments) and polypropylene (100 dtex, To observe the tensile behaviour of core 24 filaments) textured multifilament yams were component inside the yam matrix of the used as core materials. The physical properties of composite yam, the sheath fibres were removed the multifilament yams are shown in Table 1. from two ends of the yam sample and then the bare 2.2 Methods filament core was clamped with the jaws of the tensile tester. The cross-head speed and gauge 2.2.1 Preparation of Yarn Samples length were maintained as mentioned above. Yam samples were prepared on the three• headed dref-2 laboratory model spinning frame at 2.2.3 Measurement of Bending Rigidity a delivery speed of 130 m/min, inlet speed of 2.2 The bending rigidity, expressed as specific m/min and spinning drum speed of 3400 rpm. Four flexural rigidity, was measured by the ring-loop types of y.am, namely polyester-acrylic, nylon• method as suggested by Carlene 6. Ten tests were acrylic, polypropylene-acrylic core-sheath yams carried out for each sample. Specific flexural and acrylic staple fibre yam without core, were rigidity was determined using the following prepared. In case of core-spun yams, the core formula: filament yam was fed axially to the spinning drum Specific flexural rigidity through a core yam feed system attached to the = { 0.0047 W (21t r)2 cosS /tan8 }(tex)2 Table I-Physical properties of multifilament yams used as core materials where W is the weight (mg) of rider hung to deflect the bottom loop; r, the radius of ring loop; 8 = Property Polypropylene11.1623.53460.3027.3439.7680\0020.3032.4034.7052.46Nylon30.0023.5150.90208.003.53 6 Polyester348.8020.8038.932\.5534.6519.042.3290 493xd/21t r; and d, the deflection of the bottom end Tenacity,BreakingElongationSpecificStrengthrupture,extension, cN/texwork extension,CY mJ/tex at % cN/texF ofmax' -% m ForceModulus decay', at 0.5% % • ForceLinear decay density,dtex (%) at load equivalent to I% extension of ring loop under action of load.

2.2.4 Evaluation of Packing Coefficient Packing coefficient of dref yams was computed from the ratio of the bulk density of yam and fibre density7. Yams diameter was measured in projection microscope with a magnification of 40 under constant tension. Fibre density in core-spun dref yam was calculated using the following formula: 10 INDIAN 1. FIBRE TEXT. RES., MARCH 1998

Fibre density of yarn without core is significantly lower than those core - spun yarn of the other three samples, its elongation is more or 100 less same. Fig. 1 shows that when a core-spun yarn is extended by an applied load, initially both core - .-% ..-- of acrylic ..--.---- fibre + ------. % of filament and sheath components share the load density of acrylic fibre density of filament simultaneously. The sheath component, which consists of twisted staple fibres, is subjected to 2.2.5 Evaluation of Mass Irregularity and Hairiness strain up to breaking point at first due to slippage Uster yarn evenness tester (model UT-3) was between the staple fibres. As soon as the sheath used to evaluate yarn mass irregularity imper• component disintegrates the core element has to fections and hairiness index at a speed of 200 bear a very high load and catastrophic break mlmin for 2.5 min. Three tests were carried out for occurs. Work of rupture(WOR) gives the each sample. combined effect of tenacity and breaking elongation of a yarn. Table 2 shows that WOR of 3 Results and Discussion 20 3.1 Effect of Physical Properties of Core Filament -.-.- Polyester/Acrylic 3.1.1 Tenacity, Elongation and Work of Rupture ---- PP/Acrylic Nylon / Acrylic. Table I shows that the tenacity of nylon 6 z 15 filament is slightly lower· than those of polyester ...... 100·/. Acrylic and polypropylene. Polyester and polypropylene -g filaments show almost same tenacity. A similar ~ 10 trend is also observed in case of dref-spun yarns 01 C (Table 2). ~ o 5 Elongation of all the three core-spun yarns is ~ G) more or less same though the three filaments show a wide variation in their elongation properties. The D_ typical load-elongation curves for the four types of O 5 10 15 20 30 dref-spun yarn are shown in Fig. 1. It is interesting Ext en si on ,·1. to observe that even though the tenacity of acrylic Fig.1-Load-extension curves for various dref-spun yarns y.Polypropylene0:10011.101211.245.654113.6113.18\3.233.1037.50120.54736.987.8042.209.258.8621.660.4940.4220.688688.074.028.169.255.9314714714530.005:957'.93Nylon36.1420.5119.405559.90 01.260.803Acrylic core yarn coreTable20.0031.480.47682.206:949.307.147.338.22\.3513.0146539 2-PhysicalI 100% properties of dref-spun yarns Hairiness index Neps (+200%) ThickCore:sheathStrengthThinSpecificElongationTenacity,SpecificMassmNmJ/tex-cN/tex placesplaces: irregularity(mmltex workCY flexural mcN/tex ratioat(+50%) (-50%) % F ofmax')2 rupture,rigidityx(Um),% % I0, Polyester core Modulus0/9PackingForce coefficientdecay' at 0.5% extension, "ForceLinear decay density, (%) attex load equivalent to 1% extension Core-spun acrylic yarn

"I ,,', 'I' I 't II !'III CHAUDHURI & BASU: DREF-SPUN ACRYLIC YARNS 11 core-spun yams is much higher than that of the acrylic yam.

3.1.2 Modulus at Initial Stage of Extension z Even though the nylon filament shows higher ';3o modulus as compared to the other two filaments .0 before spinning, the dref-spun yam made out of it ...J shows much lower modulus than the other two dref-spun yams (Table 2). It may be observed from Fig. 2 that nylon core shows frequent stick-slip effect from very initial stage of stress development PP/Acrylic during loading. The sliding of acrylic sheath fibres PolYE'ster/Acrylic Nylon/Acrylic over nylon surface may be the reason for low o initial moduius of nylon core acrylic yam. o 5 10 15 20 25 Extension ,I. 3.1.3 Stress Relaxation Stress relaxation gives an indication of the Fig.2-Rupture of core filament bundle held under the jaws of the tensile tester after the removal of sheath fibres at the dimensional stability of yam and fabric made out gripping portions of it. Acrylic yam without core shows maximum stress relaxation ( Table 2). This may be due to the case of nylon core yam, the specific flexural poor orientation8•9 of staple fibres in the yam rigidity is lower than those of other two core-spun matrix. On the other hand, the presence of parallel yams. A similar trend is also observed in case of bundle of filaments which are oriented along yam their initial modulus values. This "isbecause of the axis might have helped to reduce the extent of slippage of sheath fibres on the nylon core. force decay in the core-spun yam. The results show that the stress relaxation of core-spun yam is 3.3 Packing Coefficient directly related to the stress relaxation of filament The packing of fibres in acrylic staple fibre yam yam used as core. Stress relaxation is highest in without core is denser as compared to that in core• case of polypropylene multifilament followed by spun yams ( Table 2). Among the three types of polyester and nylon and a similar behaviour has core-spun yam, nylon-core yam shows the highest also been observed in case of core-spun yams. It value of packing coefficient followed by polyester may be assumed that at low extension, the tensile and polypropylene core yams, though the behaviour of filament yam is a dominant factor of differences are marginal. the stress decay of core;.spun yam. The reasons may be that when a core-spun yam is held 3.4 Yam Mass Irregularity, Imperfections and Hairiness extended at low extension, the major amount of the Index stress developed in the core-spun yam is shared by The mass irregularity (Urn %) of all the three the continuous parallel filaments and at the same types of dref-spun core yam is more or less similar time the slippage of staple fibres is restricted, to (Table 2). No significant differences are observed some extent, by the core filament yam as the staple in number of imperfections for the dref-spun yams. fibres wrapped round the filament. It is also observed from Table 2 that acrylic staple fibre yam is highly irregular as compared to core• 3.2 Specific Flexural Rigidity spun yams. This is because of more instability in In weaving and tufting, the yams are generally yam formation in case of acrylic yam. Hairiness subjected to bending through a large angle and index values of all the four types of yam are more therefore rigidity of yam is an important factor in or less same. determining the equilibrium state of the final structure. It may be observed from Table 2 that the 4 Conclusions· specific flexural rigidity of core spun yams is 4.1 Tenacity and work of rupture of core-spun apparently dependent on their initial modulus. In acrylic yams are higher than those of acrylic yam 12 INDIAN 1. FIBRE TEXT. RES., MARCH 1998 without core though the breaking elongation is Mazumder, Acting Principal, Institute of Jute more or less same for all types of yam. Technology, Calcutta. They are also thankful to Mr 4.2 Use of filament results in an increase in K K Dalapati, Mr M Bhowmik and Mr S Maity for regularity of yam in respect of mass irregularity their valuable assistance. and strength CV % . References 4.3 Acrylic staple fibre yam without core I Louis G L, Salaun H L & Kimmel L B, Text Res J, exhibits more compact structure as compared to 55(1985) 344. core-spun acrylic yams. 2 Brockmanns K J, Int Text Bull, Yarn Forming, (2) (1984) 5. 4.4 More slippage between sheath fibres and 3 Padmanabhan A R & Ramakrishnan N, Indian J Fibre Text multifilament core apparently occurs when the Res, 18 (1993) 14. 4 Gebauer E & Schlossarek B, Text-Prax Int, (1990) 1041. nylon core spun yam is subjected to tensile force. 5 Miao M, How Y L & Ho S Y, Text Res J, 66 (1996) 676. 4.5 Nylon core gives considerably lower 6 Carlene P W, J Text Inst, 41 (1950) T 159. flexural rigidity of the resultant yam. 7 Bhattacharya G K & Sengupta P, J Text Assoc (India), 46 (1985) 160. 8 Lord P R, Joo C W & Ashizaki T, J Text Inst, 78 (1987) Acknowledgement 234. The authors gratefully acknowledge the support 9 Lunenschloss J & Brockmanns K J, Int Text Bull, Yarn received during this work from Dr. A K Forming, (3) (1985) 29.

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