Indian Journal of Fibre & Textile Research Vol. 27, March 2002, pp. 44-47

Influence of process parameters on flexural rigidity and elastic recovery of polyester OE rotor-spun yarns

G K Tyagia & A Patnaik

The Technological Institute of Textile & Sciences, Bhiwani 1 27 021 , India

and

S M Ishtiaque

Department of Textile Technology, Indian Institute of Technology, New Delhi, 1 10 0 1 6, India

Received 23 October 2000; accepted 9 January 2001

Fibre cross-section is an important factor in determining flexural rigidity and elastic recovery of DE rotor-spun yams. The level of spin finish, tex twist factor, draw-off nozzle profile, rotor speed and opening roller speed have profound influence on flexural rigidity. The variation either in twist factor or in rotor speed hardly affects elastic recovery; the elastic recovery, however, increases with the increase in level of spin finish. The increase is highly dependent on the draw-off nozzle profile and opening roller speed.

Keywords: Circular fibre, Elastic recovery, Flexural rigidity, Polyester yam, Spin finish, Trilobal fibre, Wrapper fibre

1 Introduction The quality of any yarn · is governed by the

properties of the constituent fibre and the spinning conditions. In rotor spinning, these will obviously be dependent, to a considerable extent, on the design of the components and the spinning parameters used. The fibre properties include strength, length, fineness and crimp. Other influencing variables in yarn quality are the level of spin finish and the cross-sectional shape of the fibre. The fibre cross-section determines the degree of stiffness, and hence the fabric handle l . The influence of fibre and machine parameters on rotor yarn quality has been thoroughly studied2-5• There are occasional references to the bending properties of yarn in the literature6-8• However, no publication regarding the contribution of fibre profile to yarn quality is available so far. The present work was, therefore, undertaken to establish a more indepth understanding of the influence of fibre cross-sectional shape and other processing factors on flexural rigidity and elastic recovery of polyester OE rotor-spun yams.

2 Materials and Methods 2.1 Preparation of Yarn Samples

Four sets of 29.5 tex yams were spun from three

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different polyester staples of linear densities 1 .66 and 2.22 dtex, and length 44 mm on rotor spinning machine using different process parameters. The coversion to drawn sliver was carried out by using a Platts' carding machine and a Lakshmi Rieters' draw­frame DOI6. Two drawing passages were given to all the samples. The linear density of finisher sliver was adjusted at 3.0 ktex. The slivers were spun into yam on Ingolstadt rotor spinner RU I I IRU 80(4602). The process parameters used to produce these yam samples are given in Table I .

2.2 Tests All the yarns were tested for flexural rigidity and

elastic recovery on a Shirley weighted ring yarn stiffness tester by the ring loop method9. For each sample, fifty observations were taken for each yarn property studied.

3 Results and Discussion 3.1 Flexural Rigidity

Figs 1 -3 show the influence of fibre cross-section, draw-off nozzle profile, level of spin finish and opening roller speed on the flexural rigidity of polyester OE rotor-spun yarn. It is observed that the yams spun with a trilobal fibre have substantially higher flexural rigidity than the yams spun with fibre of circular cross-section. However, the flexural rigidity, in general, depends on the processing factors.

TYAGI et al. : POLYESTER OE ROTOR-SPUN YARNS 45

Table 1 - Spinning parameters for rotor-spun yarns [Yarn linear density, 29.5 tex]

"� 10

'" � 8 x ,.,

Yarn ref. no.

S I S2 S3 S4 S5 S6 S7 S8 S9 SIO S " S I2 S I3

Fibre linear

density dtex

1 .66 1 .66 1 .66 2.22 2.22 2.22 2.22 2.22 2.22 1 .66 1 .66 1 .66 1 .66

Fibre Level of Tex twist profile spin factor

finish %

Circular Nil 43.06 Circular Nil 52.63 Circular Nil 57.42 Circular Nil 43.06 Circular Nil 52.63 Circular Nil 57.42 Trilobal Nil 43.06 Trilobal Nil 52.63 Trilobal Nil 57.42 Circular Nil 38.28 Circular 0.05 38.28 Circular 0. 1 0 38.28 Circular 0. 1 5 38.28

__ 2.22 ..... CRular, 833.33 rpo ___ 2.22 ..... CRuIw, 1000 rpo __ 2.22 ..... Trlo ... I, 833.33 rpo ___ 2.22 ..... T_I, 100CM1 rpo ___ 1 .00 diu. CIraMr. 833.33 'PI i6

J ���������������� 2 �--------------�--------------� 43.06 52.63 57.42

Tex Twist Faclor

Fig. I-Variation in flexural rigidity with twist factor

" 10 r-------------------------------� � Plain Nozzle --O%Spln Finish '" ___ O.OS%Spin Finish � 8 _�o%_ Finish • -of-0.15%500 Finish x �6 .2' i 41���� � � 2 �--------------�--------------�

1 16.66 133.33 150.00 Opening Roller Speed, rps

Fig.2-Variation in flexural rigidity with opening roller speed

The increase in twist factor increases the flexural rigidity due to the increased fibre cohesion which leads to increased clustering of fibres in the yarn. Consequently, more and more fibres group together and act as one unit. In addition to this, the higher incidence of wrapper fibres in the yarns spun with high twist also impairs the freedom of fibre

Draw-off nozzle profile

Plain Plain Plain Plain Plain Plain Plain Plain Plain

PlainINotched PlainINotched PlainINotched PlainINotched

� 10

� 8 � " 1 6 II:

) 4 -F' 2

0

Rotor speed

rps

833.33/1000 833.3311000. 833.33/1000 833.33/1000 833.3311 000 833.33/1000 833.33/1000 833.33/1000 833.33/1 000

833.33 833.33 833.33 833.33

Opening roller speed

rps

1 16.66 1 1 6.66 1 16.66 1 16.66 1 16.66 1 16.66 1 1 6.66 1 1 6.66 1 16.66

1 1 6.6611 33.331150 1 1 6.66/1 33.33/150 1 16.66/1 33.33/150 1 1 6.6611 33.331150

__ 1111 .• !pi. PI8in _ __ 133.33 rpo, PI8in _ -..- 150 !pi. PI8in _ ___ 118 .• rpo, � _ ___ 150 _ � _

0.05 0.10 Level of Spin Finish, %

0.15

Fig.3-Variation in flexural rigidity with level of spin finish

movement. Rotor speed is an another important factor in controlling yarn rigidity. As is evident from Fig. 1 , the flexural rigidity consistently increases with the increase in rotor speed. However, the increase in flexural rigidity with the increase in rotor speed is less marked in the yarn spun from fine denier fibres.

With respect to the application of spin finish, the yarn flexural rigidity shows dramatic trends, indicating that the opening roller speed has more profound influence on flexural rigidity in the presence of spin finish than that it does without spin finish (Fig. 2). As compared to the yarns spun with different levels of added spin finish, the flexural rigidity of yarns spun without adding spin finish initially decreases with the increase in opening roller speed and then increases at the opening roller speed of 1 50 rps owing to the deterioration in fibre straightness and degree of alignment along the yarnlO• In case of yams produced with different levels of spin finish, the

46 INDIAN J. FIBRE TEXT. RES., MARCH 2002

flexural rigidity values exhibit an ascending trend with the increase in opening roller Speed . Among the three different opening roller speeds studied ( 1 16.66, 133.33 and 1 50 rps), the 1 50 rps produces more rigid yams. This is expected to be the consequence of higher fibre-to-fibre friction which limits the fibre separation and hence demands higher opening roller speed.

Further, with regard to the influence of spin finish on yam flexural rigidity, at the same opening roller speed the yams spun with higher level of spin finish show higher flexural rigidity than the yams spun with lower level of spin finish for both types of draw-off nozzles. This may be due to the increased cohesiveness of the fibres in the yam on account of the higher fibre-to-fibre friction, which restricts the freedom of fibre movement during bending. On the other hand, the flexural rigidity is affected by draw­off nozzle profile at all the opening roller speeds studied. Fig.3 shows that the flexural rigidity is significantly higher for the yams spun with a notched draw-off nozzle than that for the yarns spun with a plain draw-off nozzle. This is due to the fact that the notched draw-off nozzle adds false twist to the strand which ultimately increases the number of wrapper fibres I I . The higher incidence of wrapper fibres limits the freedom of fibre movement.

3.2 Elastic Recovery Figs 4-6 show the effects of different processing

factors on the elastic recovery of polyester OE rotor­spun yams. In general, the yams spun with trilobal fibres have substantially higher elastic recovery. Both the rotor speed and twist factor hardly affect the elastic recovery, although the yarns spun from polyester fibres of coarse denier do exhibit considerably lower elastic recovery owing to the more unfavourable formation of wrapper fibres in the yams. Spin finish also seems to influence elastic recovery. As can be observed from Fig. 6, the minimum elastic recovery is obtained for the yams spun without spin finish and it markedly increases as the level of added spin finish increases to 0. 15%. This can be ascribed to the higher fibre-to-fibre and fibre-to-metal frictions obtained as a result of spin finish. This is due to the greater yarn twist with higher fibre-to-metal friction and higher inter fibre friction owing to the higher fibre-to-fibre friction. With opening roller speed, the yam elastic recovery exhibits distinct trend. Invariably, the elastic recovery of the yarns spun with 0, 0.05 and 0. 10% spin finish decreases with the

� �----------------�����----, __ 222 _. Clrcwa'. e33.33 rpa -+-222 -. Clrcwar. 1000 rpo ___ 2.22 -, Ttlobel. 833.33 rpa � :::::�==.�;rrpo f�r------�--! a:: g ) 40 w

� +---------------�------------� 43.06 52.03 57.42

Tex Twist Fedor Fig.4-Variation in elastic recovery with twist factor

�

*. 60 � i '" ,g 40 !! w

PIIIin Nozzle

20 1 16.66

__ O%Spin Finioh ...... O.05%Spin Finioh __ O.lo%Spin Fonioh ___ O.15%S<in Finish

:::::::::::::-- ---.,

133.33 150.00 Opening Roller Speed. rps

Fig.5-Variation in elastic recovery with opening roller speed

60

� i-.. 60 § II: 0 .t\ m 40 �

It-

20 o

__ 116.158 rpa. Plain Nozzle ........ 133.33 rpa. PIain _ __ 1 50 rpa. Plain _ __ '10.8O r",. _ _ .....- 150 'PI. NoIcIled NoUie

-::::::::===--:: --

o.os 0.10

leY .. 01 Spin Finish. 'Ib

-= -

0.15

Fig.6-Variation in elastic recovery with level of spin finish

increase in opening roller speed. However, for 0. 15% level of spin finish, the elastic recovery does not change much as the opening roller speed is increased. The decrease in elastic recovery at higher opening roller speed arises due to the greater fibre damage. This is born out by the fact that the fibre breaking extension of 28.8% reduces to 25.6% after opening at 1 50 rps, irrespective of the process parameters.

4 Conclusions Polyester OE rotor yarns spun from trilobal fibres

possess considerably higher flexural rigidity and elastic recovery than the equivalent yams spun from a

TYAGI et al. : POLYESTER OE ROTOR-SPUN YARNS 47

fibre with circular cross-section. The flexural rigidity initially decreases with the increase in both the level of spin finish and opening roller speed and then increases on further increase in the level of spin finish from 0. 10% to 0. 15% and opening roller speed from 133.33 rps to 1 50 rps. A finer fibre, lower tex twist factor, lower rotor speed and a plain nozzle are needed to reduce rigidity. The variation either in tex twist factor or in rotor speed hardly affects elastic recovery of rotor yarns; the elastic recovery, however, increases with the increase in level of spin finish. The increase is highly dependent on the draw-off nozzle profile and opening roller speed.

References 1 Matsudaira M, Tan Y & Kondo Y, J Text Inst, 84 ( 1993) 376. 2 Barella A & Vigo 1 P, J Text Inst, 68 ( 1 977) 407. 3 Steadman R G, Gipson 1 R, Mehta R D & Soliman A S, Text

Res J, 59 ( 1989) 371 . 4 Marino P N , Garofalo 1, Barella A & Manich A M, J Text

Inst, 75 ( 1984) 23. 5 Barella A & Manich A M, J Text Inst, 79 ( 1988) 1 89. 6 Thierron W, J Text Inst, 76 ( 1985) 454. 7 Dhingra R C & Postle R, J Text Inst, 67 ( 1 976) 426. 8 Kaushik R C 0, Tyagi G K & Salhotra K R, Indian J Text

Res, 1 2 ( 1987)220. 9 Owen 1 0 & Riding G, J Text Inst, 55 ( 1 964) T414.

10 Ulku S, Bipek B & Acar M, Text Res J, 65( 1995) 557. I I Lunenschloss 1, Coll-Tortosa L & Phoa T T, Melliand Textil­

ber, 57 ( 1976) 429.