Indian Journal of Fibre & Textile Research Vol. 24. March 1<)<)<). pp. 21-26

Influence of fibre length and opening roller speed on physical properties of OE rotor-spun viscose yams

G K Tyagi & s Dhamija

The Technological Institute of Textile & Sciences, Bhiwani 127 021. India

and

K R Salhotra

Department of Textile Technology, Indian Institute of Technology, New Delhi I 10016, India

Received 28 December 1997; revised received alld accepled 7 April 1998

The Innuence of sliver preparation and opening roller speed on the properties of OE rotor-spun viscose yams spun from fibres of different lengths has been studied. It is observed that the longer fibres offer no advantage to yam tenacity, breaking extension. mass irregularity and abrasion resistance. Each of these parameters shows an improvement initially with the Increase In opening roller speed but they decline with further increase in opening roller speed. Such decline in quality at high opening roller speeds, however, is less marked in the yams spun from slivers produced with two draw frame passages.

Keywords: Opening roller speed, Rotor spinner, Rotor-spun yarn. Sheath fibres, Twist efficiency, Viscose yam

1 Introduction In the past few years, the opening roller system of

fibre separation In rotor spinning has received a great deal of attention. Numerous studies have been made to elucidate Its Influence on fibre and yam properties. However, much of the work done is based on the yams spun to the same linear density from the fibres of different quality though having the same staple length and fineness. Dyson I showed that the choice of opening roller speed can significantly affect the properties of OE rotor- spun yams due to fibre breakage. He found that the fibre breakage can be minimized hy using low slIver linear density. high speed of silver Input, lower opening roller speed and low wire point density on the opening roller. Salhotra and Chattopadhya/ proposed a model based on the number-length relationship of fibres before and after the breakage. Barella and VigoJ reported that the Inadequate opening roller speed leads to deterioration In yarn tcnacIty and regulartry. Salhotra el al. 4

observed that the number of fibres that break increases as the opening roller speed increases. Simpson and Murra/ found that an opening roller Wire front (forward rake) angle of IS" yields better results In terms of yam strength. fibre parallelization and trash huIld-up In the rotor. Salhotrah studied the Influence of libre separation in rotor spinning on fibre lcn(lcity and twist efficiency. In a recent study.

Kong el al. 7 showed that the yam unevenness and

incidence of imperfections improve as the wire points per fibre increase and after reaching a critical value, there is a deterioration in these properties. The present paper reports the influence of sliver preparation and opening roller speed on the properties of OE rotor­spun viscose yams spun to different linear densities from fibres of different lengths.

2 Materials and Methods

2.1 Preparation of Yarn Samples Two sets of viscose rayon staple fibres (1.66 dtex,

38 and 44 mm, 24.24 cN/tex) were processed on a MMC card and a draw frame to produce a finisher sliver of 3.36 ktex. The drawn slivers were spun on the Ingolstadt Rotor Spinner RU 11IRU 80 (4602) into 29.5 and 59.5 tex yams with 700 and 500 tpm respectively using three opening roller speeds, VIZ. 83.33, 100 and 116.66 rps. The process parameters used to produce these yams are given in Table I. The spinning trtals tor all the yams Included a 48 mm rotor running at 40,000 rpm, a saw-tooth opening roller (type of clothing, OS/2 I ; teethlcm2

, 24 ; and face angle, 100°) and a notched nozzle with exterior diameter of 3 mm. To determine the impact of suppressing one draw frame passage, the carded slivers were divided mto two portions: (\) slivers with one passage of drawing; and (ii) slivers with two

22 INDIAN 1. FIBRE TEXT. RES., MARCH 1999

Table I-Spinning parameters for rotor-spWl yarns

Yarn Yarn Fibre length Draw Rotor speedx I 03 Tex twist Opening roller speed ref. no. linear density nun frame passages rpm factor rps

tex

SI 59.5 38 I 40 38.56 83.33/100/116.66 S2 59.5 44 I 40 38.56 83.33/100/116.66 S3 59.5 38 2 40 38.56 83.33/100/116.66 S. 59.5 44 2 40 38.56 83.33/100/116.66 ~5 29.5 38 I 40 38.01 83.33/100/116.66 S6 29.5 44 I 40 38.01 83.33/100/116.66 S7 29.5 38 2 40 38.01 83.33/100/116.66 S8 29.5 44 2 40 38.01 83.33/100/116.66

Table 2-ANOV A test results

Process Yarn properties parameters Twist Tenacity Breaking Work of Regularity Abrasion

efficiency extension rupture (U%) resistance

A s s S 5 S s B s s S tJs S S

C s s S 5 S s D s s S tiS S s

A*B ns ns ns s s A*C s s s ns s ns A*D s s ns ns s ns I3*C ns ns ns ns ns ns B*D ns ns ns ns ns s C*D ns ns s ns ns ns

A*B*C ns ns os tJs ns ns A*B*D ns ns ns ns ns s A*C*D ns ns ns tiS ns ns B*C*D ns ns ns ns ns ns

A*B*C*D ns ns ns ns ns ns

s-Si2nifi cant at 99 % confidence level; and ns-Non-significant at 99 % confidence level A-Yarn tex; B- Fibre length; C-Draw fidITle passages; and ~pening roller speed

passages of drawing. Each portion was drawn on a Lakshmi Rieters' DO/6 draw frame to give six slivers. Care was taken at both the heads of drawing to avoid any end reversal.

2.2 Tests

The single yarn tenacity and breaking extension were detennined on an Instron tensile tester using 500 mm test specimen and 200 mmlmin extension rate. The mean yarn strength and extension were averaged from 50 observations for each yarn sample. Apparent twist in all the yarns was detennined by Eureka twist tester usmg detwist-retwist method. Forty test specimens were tested for each' case. The flex abrasion resistance of yarns was detennined by a Custom scientific abrasion tester and the yarn unevenness on an Uster evenness tester. Work of rupture was calculated from the following expression: Work ofrupture=1/2 Yarn tenacityxBreaking extension

(g/den) (expressed as fraction)

3 Results and Discussion The effect of four experimental variables, viz. fibre

length, opening roller speed, draw frame passages and yarn linear density, on the yarn properties was evaluated with the help of ANOV A analysis (Table 2); the confidence level used was 99%. Except a few two-way interactions involving yarn Imear density, most of the interactions have been found to be insignificant.

3.1 Twist Efficiency

Table 3 shows the values of twist efficiency with respect to different process parameters. It is seen that as the fibre length is increased from 38 mm to 44 mm, there is a significant drop in twist efficiency. Yarn linear density also seems to influence twist efficiency. A decrease in twist efficiency is seen with the increase in yam linear density. Increasing the number of draw frame passages from one to two increases the twist efficiency, which further increases as the

TV AGI et al.: ROTOR-SPUN VISCOSE YARNS 23

Table 3--Effect of fibre length, draw frame passages, yam tex and opening roller speed on twist efficiency, regularity and abrasion resistance of OE rotor-spun viscose yams

~ ~

>-u C ...

. ~ -~

~

~ I-

Yam Twist efficiency, % ref. 83.33" 100.00' 116.66' no.

SI 76.39 79.54 80.56 S2 74.22 76.58 78.64 SJ 77.45 81.36 83.60 S4 75.98 78.02 80.63 S5 84.56 86.02 87.41 So 82.88 84.15 85.95 S) 88.56 89.82 90.77 SK 8708 88.15 89.65

"Open In.l! roller speed in rps

100

90

80

70

60

50

mm 595 tpx ,38mm.l OF ~ 595 tpx,38mm, 2 OF

o 29.5tpx,38mm,lDF ~ 29 5tpx,I.Lmm,10F

~ 295Ipx,38mm,2Cf' D 295tpx,LLmm,20F

10000 11666 Oppn.nq roliN sp~('d . rps

83.33"

10.3 10.8 9.7 10.1 11.6 11.7 9.9 10.1

Fig. I-Variation of twist efficiency with opening roller speed

openmg roller speed increases (Fig. I) owing to a decrease in the percentage of sheath fibres. The decrease in sheath fibres occurs due to the better indi,-":idualization of fibres at higher opening roller speeds, which reduces the possibility of some fibres becoming wrappers just because they happen to be entangled with the fibres undergoing formation into belts6

3.2 Unevenness and Imperfections

The effect of fibre length, yam linear density and opening roller speed on yam unevenness (U%) is shown in Table 3 and Fig. 2 and that on imperfections in Table 4, It is observed that yam unevenness decreases as the opening roller speed increases from 83.33 rps to 100 rps, but then increases considerably at 116.66 rps . The high yam unevenness at low and high opening roller speeds can be attributed to the poor openmg at low speeds and high fibre breakage

Regularity, U% Abrasion resistance, cycles 100.00' 116.661

10.1 10.6 9.5 9.9 11.3 11.4 9.5 9.5

lL

~ 12

:J 10

:: 8 ... c f 6 > ~ L :J

2

o

10.5 10.7 9.9 10.0 12.1 12.3 10.3 10.4

OIIDIlj9.ljlfX. 38mm, 1 OF

[51 295tfX .38mm . 1 OF

m 29 ·5t('x . 38 mm, 2 OF

8333

83.331 100.00' 116.66'

690 598 711 636 267 256 298 288

742 611 771 654 310 284 323 301

~ 59·5tpx.38mm.20F

rill 29 ~ Il'x. LL mm. I OF

o 2951I'X,LLmm. 20F

613 558 653 614 244 208 272

280

10000 116·66 Oppning rollpr sp('pd. rps

Fig. 2-Variation of unevenness with opening roller speed

and low fibre alignment at high speeds. The higher opening roller speed increases the possibility of fibre accumulation at the inlet of the transfer channd. The influence of sliver preparation is quite predictable, with two draw frame passages producing more regular yams. The improvement is caused by improved long­and short-term irregularity of sliver.

3.3 Tenacity

Tenacity values of OE rotor-spun viscose yams as a function of opening roller speeds are given in Table 5. The use of longer fibres offers no advantage to yam quality in rotor spinning. As can be observed from Fig. 3, the maximum yam tenacity is achieved for fibres of 38 mm length which decreases slightly with fibres of 44 mm length. This may be ascribed to higher twist loss involved in spinning longer fibres8

.

With opening roller speed, the yam tenacity exhibits distinct trends. In general, the tenacity of all the yams

24 INDIAN 1. FIBRE TEXT. RES., MARCH 1999

Table 4---Effect of fibre length, draw frame passa,8es, yam tex and opening roller speed on imperfections of OE rotor-spun viscose yams

Yam Thick places/lOOO m Thin places/lOOO m NepS/IOOO m ref. no. 83.33" 100.00· 116.66' 83.33' 100.00" 116.66' 83.33" 100.00' 116.66'

SI II 7 13 8 6 9 42 31 35 S2 12 10 15 10 7 12 53 39 49 S) 8 6 II 6 4 8 35 28 31 S4 10 9 12 7 6 9 42 33 39 S5 15 12 17 II 9 12 54 43 48 S6 16 14 20 13 10 13 60 56 57 S7 II 9 13 8 7 10 45 37 38 S8 14 10 17 8 8 II 48 44 47

"Opening roller speed in rps

Table 5---Effeet of fibre length, draw frame passages, yam tex and opening roller speed on tenacity, breaking extension and work of rupture of OE rotor-spun viscose yams

Yam Tenacity, cN/tex Breaking extension, % Work of rupture x I 0'), glden ref. no. 83.33" 100.00' 116.66' 83.33"

SI 11.23 I 1045 I 1.13 S2 10.83 11.14 10.73 SI 11.62 11.82 11.53 S. 11.36 11.66 1128 S, 9.75 1039 9.73 S6 9.44 10.25 9.22 S7 10.84 11.20 10.57 SK I DA8 11.15 lOAD

"Opening roller speed in rps

" .. 11.

12

~1O z v B

v g I. .. ....

IIIITIJ C,9'itpx,38mm.l0F !:mi'i9'itpx.38mm.ZOF

o Z9-'itpx. 38mm.l0F ~ Z9'ill'x. I.l.mm.l OF

IG"'lI 29C,tpx.3Bmm.ZOF o 29'itpx.l.I.mm,ZDF

8333 10000 11666 Oppnmg rollpr spt'pd. rps

Fig. :I-Variation o1tenaeity with opening roller speed

12.1 11.8 12.6 12.5 I 1.6 1104 12.4 12.3

initially increases with the increase in opening roller speed from 83.33 rps to 100 rps and then significantly decreases with further Increase in opening roller speed to 116.66 rps. The drop in tenacity is comparatively higher for 29.5 tex yams and it further increases with longer fibres. Since the viscose fibres taken out from the rotor groove do not show any noticeable change in tenacity and breaking extension, the decrease in yam

100.00· 116.66" 83.33" 100.00' 116.66"

12.6 11.9 76 80 75 1204 11.6 72 76 70 12.9 12.4 82 86 81 12.7 12.2 80 83 77 12.1 I 104 64 71 62 11.8 I 1. I 60 68 57 12.8 12.3 74 81 68 12.6 12.0 73 79 71

tenacity at high opening roller speeds can be attributed to the shortening of fibre length and deterioration in straightness and degree of alignment along the yam9

. It may be noted that the order of drop in tenacity at high opening roller speeds is lower in the yams spun from second draw frame sliver than in the equivalent yams produced from first draw frame silver. This is expected as the fibres m second draw frame silver are more parallel and the majority hooks are fed in trailing direction, which help produce a higher degree of straightening of the fibres in the feed tube of the rotor, leading to an improved fibre deposition in the collecting groove 3

.

3.4 Breaking Extension

The breaking extension of OE rotor-spun viscose yams varies in the range of 11.1-12.9 % depending upon the process variables (Table 5). In regards to fibre length and yam tex, the breaking extension reflects similar trends as shown by yam tenacity (Fig. 4). If one thinks of the optimum breaking extension, it is observed that there is a rather different behaviour for the opening roller speeds of up to 100 rps from that for the opening roller speed beyond this limit. As is evident from Table 5, all the yams register

.,.

TYAGI el at.· ROTOR-SPUN VISCOSE YARNS 25

~ 6 .l< o L ~ II) 2

m 59')tpx.18mm. 1 OF

[D29·5 t ••. J8mm.1 OF

D29·'}tpx.18mm.20F

o LLilJ.l/o.>.:>.l.:.::J

83H

D Ifl·5 tfx.ltmm. ] OF

rm 295t.x.l.l.mm. 1 OF

029·5 In,I. Lmm. ] OF

\0000 n666 Oppnong rollfor spf.d. rps

Fig. 4~ Variation of breaking extension with opening roller speed

M I o

lID 'fl.5 t.x.18 mm. 1 OF

llil2'}5 tfx.18mm. 1 OF

~29'5 lex. ltmm. 2 OF

H33

1m5951fX 38mm . ]OF

1:rJ295 It'x.LI. mm . 10F

0]9·5 tt'x .LLmm.]OF

10(H) 0 116 ·66

Op.ning roller speed, rps

Fig. 5~Variatlon of work of rupture with opening roller speed

an Increase In breaking extension with the increase in opening roller speed from 83.33 rps to 100 rps which slightly decreases on further increasing the opening roller speed to 116.66 rps . The decrease in yam breaking extension at high opening roller speed is caused by the shortening of fibre length . However, the influence of opening roller speed is less critical for the yams spun from the twice-drawn sliver than lor the yams produced from single-drawn sliver. Obviously, the use of second draw frame passage improves breaking extension .

3.5 Work of Rupture

The effect of fibre length, draw frame passages, yam tex and opening roller speed on work of rupture is shown In Table 5. Fig . 5 shows the effect of opening roller speed on work of rupture . Expectedly, the long fibres produce yams of slightly lower work

c .2 .. 2 D <{

11m 59·5 Iex.18mm. 1 OF

D 295 tex.38mm. I OF

~ 295 tt'x. 38mm. 2 OF

~ Ifl·5 t.x. 36 m m. ] OF

m ~5t.x.1J. mm. 1 OF

o 29S tex. LL mm. 2 OF

()(),OO 11666 Opt>ning rollpr spPf'd. rps

Fig. 6-Vanation of abrasion resistance with opening roller speed

of rupture. With opening roller speed the work of rupture shows a trend 3imilar to that shown by yam tenacity and breaking extension . Here again , the impact of opening roller speed is more marked in yams produced from single-drawn sliver than in the yams spun from twice-drawn sliver.

3.6 Abrasion Resistance

The flex abrasion cycles to rupture the viscose rotor yams spun from fibres of different lengths at different opening roller speeds are given in Table 3. It is observed that the yams spun from fibres of 44 mm length yield lower resistance to abrasion than the equivalent yams spun from 38 mm long fibres. This may be attributed to the decreased cohesive force on account of decreased twist efficiency. As the fibre length increases, the sheath fibres show an upward trend, whereas the twist efficiency shows a dovmward trend6

. Consequently, the slackened coils/sheath fibres would shift easily under the action of abradant , causing a rapid exposure of yam core to the abrasive action . The relationship between opening roller speed and abrasion resistance (Fig. 6) shows a maximum that coincides with the maximum for the relationship between opening roller speed and work of rupture . An initial increase in the opening roller speed promotes fibre separation and thus enhances the abrasion resistance by improving fibre alignment. Howe\er, a further increase in opening roller speed beyond the critical limit leads to an inferior abrasion perfonnance owing to high fibre breakage . Besides this, the decrease In the number of sheath of fibres at high opening roller speeds6 also lowers the abrasion

26 INDIAN J. FIBRE TEXT. RES ., MARCH 1999

resistance lO Further, the yams spun from slivers produced with two draw frame passages show slightly higher abrasion resistance than the equivalent yams spun from single-drawn slivers.

4 Conclusions 4.1 Twist efficiency is considerably lower in coarse

yams. It Increases with either increase in the opening roller speed or decrease in staple length. The Influence of slIver preparation is minimal.

4.2 Viscose yams spun with either too low or too high opening roller speed show deterioration in evenness which becomes worse for 44 mm fibres . On the other hand, the yams spun with slivers from second draw frame show less deterioration in evenness. This suggests that the longer fibres require more Intensive preparation for successful rotor spinning .

4.3 An Increase In fibre length from 38 mm to 44 mm offers no advantage to yam qualIty in rotor

spinning. Opening roller speed has greatest influence on yam tenacity, breaking extension, work of rupture and abrasion resistance. Each of these characteristics increases initially with the increase In opening rol1er speed and then decreases with further increase in the opening roller speed .

References I Dyson E, } Text Inst , 65 (1974) 588 . 2 Salhotra K R & Chattopadhyay R, Text Res J, 52 (J 982) 3 J 7. 3 Barella A & Vigo J P, J Text Inst , 68 (1977) 263 . 4 Salhotra K R, Kamboo N S & Chattopadhyay R, Text Res J,

53 (1983) 435 . 5 Simpson J & Murray M E, Text Res J, 49 (1979) 506. 6 Salhotra K R, Text Res J, 51 (1981) 710. 7 Kong L X. Platfoot R A & Wang X, Text Res J, 66 (1996)

30. 8 Kaushik R C D, Salhotra K R & Tyagi G K, Indian J Text

Res, \2 (1987) 146. 9 Ulku S, Ozipek B & Acar M, Text ResJ, 6:5 (1 995) 557. 10 Dutta B & Salhotra K R, Indian J Text Res, 6 (1981) 60.