Indian Journal of Fibre & Textile Research Vol. 3 1 , December 2006, pp. 5 1 5-520

Effect of spinning conditions on characteristics of polyester-viscose MJS core yarns

G K Tyagj" The Technological Institute of Textile & Sciences, Bhiwani 127 02 1 , India

Received 5 July 2005; revised received 25 October 2005; accepted 21 November 2005

The effect of processing conditions in air-jet spinning on the characteristics of polyester-viscose core-spun yarns has been studied. I t is observed that the increase in main draft leads to a significant increase almost in all mechanical characteristics. Reduced yarn l i near density also has a potential for an appreciable increase in these characteristics. Increased spinning speed also provides a noticeable i ncrease in yarn tenacity, breaking extension, initial modulus, energy-to-break, flexural rigidity, elastic recovery and abrasion resistance.

Keywords: Core-srun yarn, Feed ratio, Main draft, Murata air-jet spinning, Polyester filament, Wrapper fibres IPC Code: Int. Cl. D0 1 H7/00, D02G3/00

1 Introduction Non-elastic core-spun yarns use nylon or polyester

continuous filament as the core and are covered with natural or other staple fibres. These yams are used in such articles as tarpaUlins, car safety belts and net twins, which require strength and toughness provided by the core combined with such properties as softness and suitable frictional properties derived from the sheath. Besides, swim suits, stretch fabrics and form­persuasive garments are some other applications of core-spun yams with non-elastic core. Core yams can be successfully spun on ring, rotor and friction spinning systems. Though the literature contains many references on the production and properties of core yams produced by these spinning systems 1 .8,

there is no report in regard to air-jet yams. The present work was, therefore, undertaken to elucidate the effects of feed ratio, main draft and spinning speed in air-jet spinning on the mechanical properties of polyester-viscose MJS core-spun yams. This work is also a continuation of the initial study of production and evaluation of the properties of jet-spun core yarns.9

2 Materials and Methods

2.1 Preparation of Yarn Samples

Two sets of yarns of 1 1 .8 and 1 8 .4 tex were spun from 100% polyester core (50 denier/36 filaments) and 100% viscose fibre sheath (5 1 mm, 1 . 1 dtex and

"E-mail : drgktyagi @ rediffmail.com

2 1 .06 cN/tex) on ring- and air-jet spinning machines. The polyester filament had a tenacity and breaking extension of 34.59 cN/tex and 27.32% respectively. The laps of viscose rayon fibre were made on a Lakshmi Rieters' blow room line and carded on a MMC card. The carded sliver was given three drawing passages on a Lakshmi Rieters" draw frame (DO/2S) to produce a finisher sliver of 1 .57 ktex which was than spun into yarns on Murata air-jet spinner (802 MJS) operating under normal mill conditions. The pre-tensioned polyester filament from the supply package placed at the creel, modified to accommodate the package of filament yarns, was drawn through a guide. It was accurately positioned at the center of the drafted ribbon of fibres and fed into the nip of the front drafting rollers of the Murata air­jet spinner. The twisting action produced by two nozzles causes the viscose fibres to wrap around the polyester filament core. Table 1 shows the important process parameters used for the spinning of yarns. For ring spinning, the finished drawn sliver was converted into a suitable rove using an OKK roving frame. Equivalent core yarn ( 1 1 .8 tex) was spun from the polyester filament and viscose materials on Lakshmi Rieters' ring frame G 511 using the following process parameters: spindle speed, 1 3500 rpm; total draft, 25; and tex twist factor, 33.49.

2.2 Tests

Yarn tensile properties were measured on an Instron tensile tester (Model 1 122), using 500 mm test specimen and 200mmlmin extension rate. Fifty

5 1 6 INDIAN J. FIBRE TEXT. RES., DECEMBER 2006

Table 1 - Processing parameters for MJS yarns

[Distance between first jet and the nip of front roller, 39mm; Ribbon width, 3mm; NP 1 , 3kg/cm2; and NP2, 4.5kg/cm2}

Yarn Yarn l inear Yarn type Fibre composition Feed ratio Main draft Spinning speed ref. no. density, tex (Polyester: Viscose) m/min

S I 1 8.4 Filament core 30:70 0.96/0.97/0.98 30.9 1 1 80 S2 1 8.4 Filament core 30:70 0.96 30.9 1 /35.77/4 1 .55 1 80 S3 18 .4 Filament core 30:70 0.96 30.9 1 1 80/1 90/200 S4 1 l .8 Filament core 47.53 0.96/0.97/0.98 30.9 1 1 80 S5 1 1 .8 Filament core 47.53 0.96 30.9 1 /35.7714 I .55 1 80 S6 1 1 .8 Fi lament core 47.53 0.96 30.91 1 80/ 1 90/200 S7 1 1 .8 Viscose 0: 1 00 0.96/0.97/0.98 30.9 1 1 80 S8 1 1 .8 Viscose 0: 1 00 0.96 30.9 1 /35 .77/4 1 .55 1 80 S9 1 1 .8 Viscose 0: 1 00 0.96 30.9 1 1 80

NPI - First nozzle pressure; and NP2 - Second nozzle pressure.

Table 2 - ANOV A test results

Process variable Yarn property Tenacity Breaking Init ial Energy Flexural Elastic Strength

extension modulus -to- break rigidity recovery loss

Yarn type s s s s s

Yarn tex s s s s s

Feed ratio ns ns s ns s

Main draft s s s s ns ns s

Spinning speed s s s s

s - S ignificant at 99% confidence level, and ns - Non-significant at 99% confidence level.

30 ,---,....----,---..,,-----,---.,....,-,..,,--c--c,-, r--------------, ,----------------, Main umf!. 3D.Y I : Spinning sp-,,-'ll . I SO (b) F\...,d '''Iio. 0.%: Spinning 'IlL "Cd. I RO nvmin (e) Feed ralio. 0.%: Main draft. JO.lJ I

::5

>< ::0 � -. bO _ � I �

.� 1 0 c:: � 5

s,

0.96

s, s, s,

0.97 0.98 30.91

s, s, s, s, s, s, s,

35.77 41 .55 lao 190 200

Feed ratio Main draft Spinning speed, mlmin Fig. I - Variation in tenacity of core-spun yarns with feed ratio, main draft and spinn ing speed [S I - 1 8 .4 tex MJS core yarn; S2 - I 1 .8

tex MJS core yarn; S} - 1 1 .8 tex MJS v iscose yarn; and S4 - 1 1 .8 tex ring-spun core yarn}

observations were taken for each sample. The abrasion resistance was measured in terms of strength loss with the help of Instron, and in each case the observed strength loss after 1 000 rubs was noted. The flexural rigidity and elastic recovery were measured by ring loop method. 1 0

3 Results and Discussion The effect of processing conditions on the yarn

properties was assessed for significance using

analysis of variance (Table 2). Only first order interactions were considered.

3.1 Tensile Properties

Figures 1-4 show the tensile characteristics oj polyester-viscose core-spun yarns in relation to spinning system and some process parameters. Since the fibre composition and yarn l inear densities were the same for core-spun yarns, it may be correct to assume that the differences in the tenacities of ring

TY AGI: EFFECT OF SPINNING CONDITIONS ON CHARACTERISTICS OF POL YESTER-VISCOSE YARNS 5 1 7

_, ! ,.HH_.· �· ·_ 40

",,< 35 '

... 1 1 " Main lh<lli. -'!l.l) I : Spinning sp<.'<:d. 1 �o Ill/Illin ' r\."d 1;lIio. 0.%: Spinnill),! SI,xd. I X() Ill/Illin Feed r:llill. O.lJ6: Main draf!. �(I .'I I

30

'f 25 i -= ! ;..;: 20 ! '" � 1 5 i

:1 1 0 : :.; '-:::: 5 :

o

5, 5,

0.96 0.98

5, 5,

5,

5,

30.91 �S.77 41 .55 1 80 1 90 200 0.97

Feed ratio \'lain draft Spinning speed, m/mi n

Fig. 2 - Variation i n breaking extension of core-spun yarns with feed ratio, main draft and spinning speed [S I - 1 8.4 tex MJS core yarn: S2 - 1 1 .8 tex MJS core yarn ; S3 - 1 1 .8 tex MJS viscose yarn : and S4 - 1 1 .8 tex ring-spun core yarn]

'- -1 1 400 r-"" FL'\!d I:uin. 0.\)6: Sp\l)1l1l1� �1X.'\.:d, 1 XU nVlllin I . Feed raliD. 1 1.96: Main draf!. .10.li I '" 1 200 ;

:r 5 s .. $, .;

-

--

200

0

Feed ratio \lain d ra ft Spinning Slwcd. Ill/min

Fig. 3 - Variation in in itial modulus of core-spun yarns with feed ratio, main draft and spinning speed [S I - 1 8.4 tex MJS core yarn: 52 - 1 1 .8 tex MJS core yarn; S3 - 1 1 .8 tex MJS vi scose yarn; and S4 - 1 1 .8 tex ring-spun core yarn]

\bin (b�lIl. .1n q j : SJlillllill� :-'1'\\'<1. I X( l l l vlIlin

s, s s , s,

s

() ..... ..,""'"'''--.L_.L_ 0.96 0.97 0.98 30.9 1 35 7i �, 55 '80 190 200

Feed ratio \ l a i n draft S pinning speed. IIIll11in

Fig. 4 - Variation in energy-la-break of core-spun yarns with feed ralio, main draft and spinning speed [S I - 1 8 .4 lex MJS core yarn: S2 - I 1 .8 tex MJS core yarn; S3 - 1 1 .8 tex MJS viscose yarn; and S4 - 1 l .8 lex ring-spun core yarn ]

and MJS yarns reflect the differences in the spinning processes. On comparing the tenacities of all the MJS yarns, the viscose-covered polyester fi lament yarns are found to be stronger than 1 00% viscose yarns. The statistical analysis of the data indicates that the yarn l inear density is a major contributor to the core yarn tenacity . The tenacity i ncreases considerably with the decrease in yarn l inear density . The change in yarn

tenacity is associated with the increased influence of edge fibres. The air flow at the nip of the front roller causes the edge fibres to move away from the fibre bundle and thus helps to produce long wrappings. The effect of main draft is along the predictable lines, a higher main draft results in a higher yarn tenacity. Spinning speed also has a significant effect on tenacity, and the core yarns spun at 200m/min

5 1 8 INDIAN J. FIBRE TEXT. RES., DECEMBER 2006

spinning speed register h i gher tenac i ty than those

spun with lower values of spinn ing speed due to longer wrapped i n l ength . I I

Relationships between the processi n g factors and

the breaki n g extension of MJS core yarns are shown in Fig. 2. General ly, the h i gh er the spi nn i ng speed, the

h igher is the breaki ng extens ion . As regards the breaking extension of core yarns at d i fferen t levels of

mai n draft, it is observed that a h i gher mai n draft

resu l ts in a markedly higher breaki ng extens ion. I ncrease i n feed rat io prod uces a m i n i mal effect on

break ing extension. Moreover, the values of breaki n g extension are much h i gher for MJS core yarns than

for 1 00% vi scose and ri ng-spun core yarns, and these further i ncrease s ignifi cant l y when yarn l i near densi ty

decreases and, at the same t i me when s p i n n i n g speed i ncreases.

F igures 3 and 4 reveal the i n i t ia l modulus and

energy-to-break u nder various processi ng condi t ions .

I n variably, MJS core yarn records l ower i n i t ial modulus and lower e nergy-to break than the ring-spun core yarn. Of the MJS yarns, those w i th a polyester

fi lament core yie ld h igher i ni t ial mod u l u s and energy ­

to-break than a pure v i scose yarn. The stati st ical analysis of the data i n dicates that the spi n n i ng speed

and feed ratio have a s ignifi canr i ntl uence on i n i t ial

modulus with F-ratios of 1 1 7 .6 and 1 34.9 respectively. The res u l t s are s i m i l ar for energy-to­break. H igh feed ratio and sp inning speed tend to

i ncrease the i n i t i al mod u l u s and energy-to-break; th is i s general l y true for core as wel l as pure v i scose yarns. Both i n i ti al mod u l u s and e nergy-to-break

i ncrease w i th i ncreasi n g main draft, which i s

reasonab l e s i nce h igher main draft woul d tend t o increase the wrapper fibres which effect ively b i nd the

core. On i ncreasi n g yarn l i near density, however, both

" 1 0 r

i n i tia l mod u l us and energy-to-break decrease due to decreased edge fibres.

3.2 Flexural Rigidity The flexural rig i d i ty values for r ing and MJS core

yarns are shown i n Fig. 5 . The common observat i on

that MJS yarns are more rigid than ring-spun yarns

holds true for core yarns too. In MJS core yarns, the

paral lel polyester fi laments b i nd by t ight wrapper

fi bres al low l i tt le freedom of their movement duri ng

ben d i ng. An i ncrease ei ther in feed ratio or i n main draft does not cause a s i g n i fi cant i ncrease i n the flex ural rigid i ty ; the l ater, however. decreases when

both yarn l i near density and spi n n i ng speed decreaSe.

This is because s lower speed l eads to a reduction i n wrapper fi bres.

3.3 Ahrasion Resistance The l'l ex abrasion res i s tance measured i n terms 0 1'

strength loss after 1 000 rubs i s shown i n F ig . 6. The abras ion res i stance o f MJS eore yarn is lower than thl' ring-spun core yarn . Whi l e the strength loss of J J . I< lex ri ng core yarn i s abou t J 8 .8%, i t i s 40.0-45 .2(k r<l : J J . 8 l e x MJS core y a rn s a n d 4 1 .4-46 .3% for J 1 .8 tex pure vi scose yarns. The m i croscopi cal exami nation �) r the photographs of the yarns produced with coloured

fi lament s hows that the core surface is a i most total l y

covered w i th v i scose s taple a n d shows no sign o f i nter

ply i ng between the polyester core and the vi sco:'>e

sheath, i ndicati ng that the yarn can be effect i ve ly

processed and u t i l ized. However, J 8.4 tex polyester­vi scose MJS core yarn produced w i th 30170 core­sheath ratio e x h i b i ts the h ighest cover factor. A

statisti cal analysis of the data reveals that the feed rat io and spin n i n g speed i m prove the abrasion

res i stance. The i mprovement i s the consequence of

::: ' � �bill lll:th . . ,0 ') I : Spilillillt! 'I>.:cti. I XU I 1lIlIIill Fecd r:llio, O.9(): SI'I I I I l I I I� 'llI:l'l1. I so m/min I '

; ;.( 8 ; s ,

;.. .

It 4 '-

;.: , 2 , z ::-

..... 0 0.96 0.97 0.98

Fced ratio

s. s,

30.91 35.77 4 1 .55

!\Iain draft 1 80

S. 5,

190 200

Spinning spced, Ill/min

Fig. 5 - Variation in flexural rigidity of core-spun yarns with feed ratio. mai n draft and spinning speed [S f - 1 8.4 tex MJS core yarn : S2 - 1 1 .8 tex MJS core yarn; SJ - 1 1 .8 tex MJS viscose yarn ; and S4 - 1 1 .8 ring-spun core yarn]

TY AGI: EFFECT OF SPINNING CONDITIONS ON CHARACTERISTICS OF POL YESTER-VISCOSE YARNS 5 19

R:ed ratio. 0.96: Spinning spet·d. 1 80 m'min Feed ratil). 0.%: Main drart. 30. 1.) 1

t"i'. :r. £ ..c 30 e£ :: � 20 :.. :n 1 0

0

0.96 0.98 30.91 35.77 41 .55 180 190 200 0.97

Feed ratio Main draft Spinning speed. Ill/min

Fig. 6 - - Variation in abrasion resistance of core-spun yarns with feed ratio, main draft and spinning speed [S I - 1 8.4 tex MIS core yarn; Sz - 1 1 .8 tex MIS core yarns; S3 - 1 1 .8 tex MIS viscose yarn; and S4 - 1 1 .8 tex ring-spun core yarn ]

1 00

t� :, . 80 � ;. u 60

::.. :.. .� 40 -", ::: � 20

0

�-�� .. -... ------ " �'. ""'" ... .-. ........... "'.' .... ' . " ' . .. ......... · .... ··........--1 Main d,o,li. �O.9 1 : Spinning spced. 180 m/min I

s, s, fecd ralio. 0.%: Main draft. .'(J.l) 1

S, S, l

s,

0.96 0.97 0.98 30.91 35.77 4 1 .55 180 190 200

Feed ratio Main draft Spinning speed, mlmin

Fig. 7 - Variation in elastic recovery of core-spun yarns with feed ratio, main draft and spinning speed [S I - 1 8.4 lex MJS core yarn; Sz - 1 1 .8 tex MIS core yarn; S3 - 1 1 .8 tex MIS viscose yarn; and S4 - 1 1 .8 tex ring-spun core yarn ]

the increased number of wrapper fibres and wrapped­in length which effectively shield the core, leading to higher abrasion resistance. There is also a marked improvement in abrasion resistance with the increase in yarn linear density. This can again be attributed to the above-mentioned factors.

3.4 Elastic Recovery

Figure 7 depicts the elastic recovery values of polyester-viscose MJS core yarns produced under different processing conditions. Expectedly, coarse core yarns display lower elastic recovery. However, the mean elastic recovery increases significantly with the increasing spinning speed. This increase in elastic recovery is associated with higher transverse force arising out of increased wrapped-in length. Further, all MJS core yarns register a substantial increase in elastic recovery with the increase in feed ratio which can be attributed to the improved propagation of strain arising from improved alignment of fibres in the yarn. The effect of main draft on elastic recovery is minimal. Nevertheless, MJS core yarns have lower elastic recovery than the ring-spun core yarns owing

the shorter length of the fibre available per unit length in the former.

4 Conclusions 4.1 The most influencing factor is yarn linear

density in all fibre compositions. Higher main draft has a potential for a marked increase in the tensile characteristics. Higher spinning speed is also of marked significance from aspects of tenacity and breaking extension.

4.2 The change in feed ratio and main draft has a little effect on flexural rigidity, although the core yarns spun with higher feed ratio and main draft are more rigid. Flexural rigidity and elastic recovery increase significantly with the increase in both spinning speed and yarn linear density. Flexural rigidity also gets increased on increasing feed ratio.

4.3 MJS core yarns exhibit lower abrasion resistance than the equivalent ring-spun yarns, which, however, improves with the increase in yarn linear density. An increase in feed ratio also increases the abrasion resistance. Spinning speed and main draft are prime factors in controlling abrasion resistance, and

520 INDIAN J. FIBRE TEXT. RES., DECEMBER 2006

higher spinning speed and higher main draft are needed to improve abrasion resistance.

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