Influence of some process parameters on the properties of

Indian Journal of Fibre & Textile Research Vol. 26, September 2001 , pp.255-260

Influence of some process parameters on the properties of viscose fibre rotor-spun yams

G K Tyagi· & ReD Kaushikb

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

and

K R Salhotra

Department of Textile Technology, Indian Institute of Technology, New Delhi 110 016, India

Received 15 December 1999; accepted 28 March 2000

The influence of opening roller speed and sliver preparation on the properties of viscose OE rotor yarns spun from the fibres of different linear densi ties at high rotor speeds has been studied. It is observed that the fine fibres offer significant advantage in regard to yarn tenacity, breaki ng extension, work of rupture, abrasion resistance and mass irregularity. Each of these quality parameters improves initially but deteriorates thereafter as the opening roller speed is further increased beyond the optimum level. The rate of decline in the properties is greater when the yarns are produced at higher rotor speeds. Such decline in the properties at higher rotor and opening roller speeds is, however, more marked in yarns spun with single passage drawframe sli ver.

Keywords: Opening roller speed, Rotor-spun yarn, Twist effi c iency, Vi scose yarn , Wrapper fibres

1 Introduction The opening roller system of fibre separation in

rotor spinning evoked much interest among textile researchers and has been extensively studied over the years. As a fibre separating device, the opening roller system does an excellent job, but it invariably leads to considerable amount of fibre breakage. Breakage is influenced by the physical and mechanical properties of the fibres, the configuration of fibres in the feed sliver and feed rate, and the design of the opening roller and its speed. The influence of the opening of fibres by the opening roller on fibre properties has been studiedl.2. In addition, the effect of certain other factors on tenacity, elongation and irregularity of rotor yarns, spun from the best known fibres, has also been studied3

-9

. The investigations that form the subject of this paper, however, are concerned with the combined influence of rotor speed, sliver preparation and opening roller speed on the characteristics of viscose OE rotor yarns of different linear densities spun from fibres of different deniers. Such a study is

a To whom all the correspondence should be addressed. Phone: 42561; Fax: 0091-01664143728 ; E-mail : [email protected]. in b Present address: Director, BRCM College of Engg & Technology, Behal 127028, Bhiwani , India

important because the properties of rotor-spun yams are determined by the interaction of such parameters, many of which are determined by trial and error in the spinning mills.

2 Materials and Methods

2.1 Preparation of Yarn Samples

The raw materials used for spinning the various yams were four light (3.2 glm ) slivers of once- and twice-drawn viscose staple ( 38 mm,I .33 and 1.66 dtex, and 24.24 cNtex-' ). The yams of different counts (29.5 tex and 59.5 tex ) were produced on an Ingolstadt rotor spinner RUllIRU80(4602) operating under normal textile mill conditions. Table 1 shows the important process parameters used for spinning these yams. The spinning trials for all the yams involved a 48 mm rotor, an opening roller covered with OS21 saw tooth wire, and a spiral draw-off nozzle (external diam.,15.5mm; and internal diam., 3mm).

2.2 Tests

The single yam tenacity and breaking extension were measured on the Instron tensile tester (model 1122) using 500 mm test specimen and 20 em/min

256 INDIAN 1. FIBRE TEXT. RES., SEPTEMBER 2001

Table 1-Spinning parameters for rotor-spun yarns

Yam sample Yam linear Fibre linear Draw frame Rotor speed Tex twist Opening roller speed density, tex density, dtex passages rps factor rps

S, 59.5 1.33 I S2 59.5 1.33 1 S3 59.5 1.66 1 S4 59.5 1.66 I

Ss 59.5 1.33 2 S6 59.5 1.33 2 S7 59.5 1.66 2 S8 59.5 1.66 2 S9 29.5 1.33 S IO 29.5 1.33 SII 29.5 1.66

S'2 29.5 1.66 1 S I3 29.5 1.33 2

S'4 29.5 1.33 2

SIS 29.5 1.66 2

S'6 29.5 1.66 2

extension rate. Fifty Teadings were taken for each yarn sample. Apparent twist in all the yarns was estimated by Eureka twist tester using detwist-retwist method. Forty test specimens were tested in each case. Flex abrasion resistance of yarns was determined by Custom scientific abrasion tester. Work of rupture was calculated from the following expression:

Work of rupture = 112 [Yarn tenacity (g/d} x Breaking extension (expressed as fraction)] .

3 Results and Discussion The influence of five experimental variables, viz.

yarn tex, fibre linear density, sliver preparation, rotor speed and opening roller speed, on the yarn properties was assessed for significance using Analysis of Variance (ANOVA) (Table 2); the confidential level used was 99%. All the interactions have been found to be non-significant. Only first order interactions were considered .

3.1 Tensile Properties Table 3 shows the results of tensile tests.

Expectedly, the finer fibres produce slightly stronger yarn . The results show that there are marked differences in tenacity of yarns spun at different opening roller speeds. The increase in opening roller speed from 83.33 rps to 100 rps for both 29.5 and 59.5 tex yams leads to an increase in tenacity but the tenacity decreases with further increase in opening roller speed to 116.66 rps. Since the viscose fibres taken out from the rotor groove do not show

666.66 38.56 83.33/100/116.66 833.33 38.56 83.33/100/1 16.66 666.66 38.56 83.33/100/116.66 833.33 38.56 83.33/1 00/1 16.66

666.66 38.56 83.33/l00/l16.66 833.33 38.56 83.33/100/1 16.66 666.66 38.56 83.33/100/116.66 833.33 38.56 83.33/100/11 6.66 666.66 38.01 83.33/100/116.66 833.33 38.01 83.33/100/116.66 666.66 38.01 83.33/1 00/1 16.66 833.33 38.01 83.33/100/11 6.66 666.66 38.01 83.33/1 00/1 16.66 833.33 38.01 83.33/100/1 16.66 666.66 38.01 83.33/100/11 6.66 833.33 38.01 83.33/100/11 6.66

significant change in tenacity and breaking extension , the decrease in yarn tenacity at higher opening roller speeds is the expected consequence of the shortening of fibre length and deterioration in the straightness and degree of alignment along the yarn 10 . Invariably, the drop in tenacity is comparatively greater in 29.5 tex yarns than that in 59.5 tex yarns. As expected, the yarn tenacity decreases as the rotor speed increases.

Table 3 also shows the values of yarn breaking extension. As expected, the finer fibres result in slightly greater breaking extension. The presence of more fibres in the yarn cross-section contributes to higher tenacity and thus higher breaking extension of yarns spun from finer fibres. The effects of yarn linear density and rotor and opening roller speeds are similar to those on yarn tenacity. However, the influence of opening roller speed is less critical for the yams spun from the slivers produced with two drawframe passages.

The association of work of rupture with different process variables is shown in Table 3. It is evident that the 1.33 dtex fibres produce yarns of appreciably higher work of rupture than 1.66 dtex fibres. In regards to yarn linear density and rotor speed, the work of rupture reflects a similar trend as of yarn tenacity and breaking extension. The data indicate a sizeable increase in work of rupture with the increase in opening roller speed up to 100 rps. Further increase in opening roller speed to 116.66 rps, however, results in lower work of rupture. Here , the effect is less marked in yarns spun from the twice-drawn slivers.

TY AGI et al. : VISCOSE FIBRE ROTOR-SPUN YARNS

Process variables

A

B

C

D

E

A*B

A*C

A*D

A*E

B*C

B*D

B*E

C*D

C*E

D*E

A*B*C

A*B*D

A*B*E

A*C*D

A*C*E

A*D*E

B*C*D

B*C*E

B*D*E

C*D*E

Tenaci ty Breaking extension

s s

s

s

s

s

ns

s

ns

ns

s

ns

ns

ns

ns

ns

ns

ns

s

ns

ns

s

s

s

s

s

s

s

ns

s

ns

s

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

s

ns

ns

Work of rupture

s

s

s

s

s

s

s

ns

ns

ns

s

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

Table 2- ANOV A test results

Twist efficiency

s

s

s

s s

s

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

Abrasion resistance

s

s

s

s

s

ns

s s

s

ns

s

s s

s

s

s

ns

s

ns

s

ns

ns

ns

ns

ns

Regularity (U%)

s

s

s

s

s

s

s

ns

ns

s

ns

ns

s

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

Thick

places

s

s

s

s

s

s

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

Thin

places

s

s

s

s

s

s

s

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

s----Significant at 99% confidence level ;and ns-- Non-significant at 99% confidence level.

A-Yarn tex ; B-Fibre linear density; C- Drawframe passages; D- Rotor speed; and E-Dpening roller speed.

Table 3- Effect of fibre linear density and opening roller speed on tenacity ,breaking extension and work of rupture of OE rotor-spun viscose yams at different rotor speeds

Yarn sample

83.33"

11 .50 10.87 11 .23 10.60 11.98 11.09 11.62 11.06 9.97 9.34 9.75 9.30 10.96 10.23 10.84 10.29

Tenacity ,cN/tex

100.00·

11.87 11.03 11.45 10.87 12.32 11.50 11.82 11 .2 1 10.57 9.90 10.39 9.94 11.48 10.74 11.20 10.66

116.66 "

11 .44 10.66 11.13 10.34 11.90 10.94 11 .53 10.77 9.81 9 .12 9.73 9.04 10.94 10.14 10.57 9.90

" Opening roller speed, rps

Breaking extension , %

83.33 a

12.9 12.7 12.1 11.8 13.5 13.3 12.6 12.3 11.9 11.7 11.6 11.4 12.9 12.8 12.4 12.3

l00.00a

13.4 13.1 12.6 12.3 13.9 13.6 12.9 12.6 12.3 12.2 12.1 11.9 13.2 13.0 12.8 12.6

116.66a

12.8 12.6 11.9 11.6 13.3 13.1 12.4 12.2 11 .8 11.6 11.4 11.2 12.6 12.5 12.4 12.2

Work of rupture x 10.3, g/den

83.33a 100.00' 116.66"

84 78 76 70 91 83 82 77 67 61 64 60 79 74 74 71

90 81 80 75 96 88 86 79 74 68 71 66 85 79 81 76

82 76 75 67 89 81 80 74 65 59 62 57 78 71 68 68

Neps

s

s

s

s

ns

ns

ns

ns

ns

ns

ns

s ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

ns

257

258 INDIAN 1. FIBRE TEXT. RES. , SEPTEMBER 2001

Table 4- Effect of fibre linear density and opening roller speed on abrasion resistance, twist efficiency and regularity of OE rotor -spun yarns at different rotor speeds

Yarn Abrasion resistance, cycles Twist efficiency, % Regularity, U% sample 83.33" 100.00" 116.66" 83.33"

SI 735 787 682 89.78 S2 707 753 646 77.58 S3 690 742 613 76.39 S4 652 694 563 73.79 S5 750 805 713 81.02 S6 728 777 683 79.32 S7 711 771 653 77.45 Sg 680 735 617 77.15 S9 282 323 271 85.12 SID 264 298 244 83.52 SII 267 31 0 246 84.56 SI2 237 273 200 82.64 SI3 316 364 307 89.65 SI4 305 343 284 88.15 SI5 298 323 272 88.06 SI6 278 297 241 86.76

a Opening roller speed, rps

3.2 Abrasion Resistance The relationships between the number of abrasion

cycles to rupture viscose OE rotor spun yarns and various factors are shown in Table 4. When the opening roller speed increases from 83.33 rps to 100 rps, the abrasion resistance increases. The abrasion resistance, however, diminishes as the opening roller speed is further increased to 116.66 rps . The fewer sheath fibres and high fibre breakage at high opening roller speeds6 contribute greatly to the lower abrasion resistance. The data show a significant lowering in abrasion resistance with the increase in rotor speed. The abrasion resistance is very much related to tensile properties of yarn and reflects similar trends for di fferent rotor speeds . The abrasion resistance of 29.5 tex yarns is found to be inferior to that of 59.5 tex yarns. It is also lower when yarn is spun from 1.66 dtex fi bres in place of 1.33 dtex fibres. For all the yarns, the abrasion resistance shows a close association with the number of drawframe passages. As can be observed from Table 4, the yarns spun from slivers produced with two drawframe passages yield significantly higher abrasion resistance than their counterparts spun with single drawframe slivers.

3.3 Twist Efficiency Table 4 shows the values of twist efficiency with

respect to different process parameters. It is observed that as the fibre linear density is increased from 1.33 dtex to 1.66 dtex, there is a significant decrease in

100.00· 116.66· 83.33" 100.00· 116.~a

81.87 83.79 9.5 9.3 9.7 79.88 81.36 9.7 9.4 10.0 79.54 80.55 10.3 10.1 10.5 77.14 77.84 10.6 10.4 10.9 83.15 85.96 9.2 8.9 9.3 80.95 83.56 9.3 9.0 9.5 81.35 83.60 9.7 9.5 9.9 79.16 81.11 9.9 9.7 10.2 87.88 89.53 11.3 11.0 11.6 86.38 87.50 11.5 11.3 11.4 86.02 87.41 11.6 11.3 12.1 83.72 84.91 11.7 11.6 12.5 92.08 93.57 9.6 9.4 9.9 90.78 91.97 9.7 9.5 10.2 89.83 90.77 9.9 9.3 109.3 88.22 89.07 10.2 9.7 10.5

twist efficiency. The influence of opening roller speed is quite predictable, with higher opening roller speed resulting in higher twist efficiency. Such a behaviour of twist efficiency could arise due to the decrease in sheath fibres, which reduces the possibility of some fibres becoming wrappers just because they happen to be with the fibres undergoing formation into belts6

.

The increase in number of drawframe passages from one to two significantly affects the twist efficiency . The twist efficiency, however, shows a decline with the increase in rotor speed. As a result of higher rotor speed, the tying-in zone in the rotor becomes much longer and, therefore, the possibility of bridging fibres being picked up by the yarn increases, which results in lower twist in these fibres . However, the decrease in twist efficiency at higher rotor speeds is less in yarns spun with 1.33 dtex fibres than in yarns spun with 1.66 dtex fibres. This suggests that the fine fibres require less torque than the coarse fibres for binding into the yarn end. Because of the low torsional rigidity and high number of fibres in the yarn cross -section, it is possible to spin finer yarns at relatively low twist.

3.4 Mass Irregularity Table 4 shows that the mass irregularity (U%) of

29.5 tex and 59.5 tex yarns varies from 9.4 to 12.5 and 8.9 to 10.9 respectively. The use of finer fibres offers considerable advantage in rotor spinning in respect of yarn evenness. As may be observed from

TY AGI et al. : VISCOSE FIBRE ROTOR-SPUN YARNS 259

Table 5-Effect of fibre linear density and opening roller speed on imperfections of rotor-spun yarns at different rotor speeds

Yarn Thick places/ 1000 m Thin placeS/lOOO m Neps/lOOO m sample

83.33" 100.00" 116.66" 83.33"

SI 8 5 9 5 S2 5 7 13 7 S3 11 7 13 8 S4 13 11 15 10 S5 6 4 8 4 S6 8 7 11 5 S7 8 6 11 6 S8 11 10 13 8 S9 11 8 12 10 SIO 14 11 15 10 SII 15 12 17 11 SI2 17 15 20 12 SI3 10 9 11 6 SI4 13 9 14 7 SI5 12 9 13 8 SI6 14 II 16 II

a Opening roller speed, rps

Table 4, the yarn evenness significantly improves with the decrease in fibre linear density. This improvement in yarn evenness, however, depends on the opening roller speed and number of drawframe passages used . When the opening roller speed is increased from 83.33 rps to 100 rps, the yarn unevenness decreases considerably but increases at 116.66 rps. At lower and higher opening roller speeds, the yarn evenness deteriorates due to the poor opening, higher fibre breakage and poor fibre alignment". The increase in drawframe passages improves the yarn evenness, which, however, deteriorates at the higher rotor speeds.

3.5 Imperfections

Table 5 shows that the imperfections increase with the increase in fibre denier. Higher rotor speed also has a deleterious effect on the imperfections. For both 29.5 tex and 59.5 tex yarns, the imperfections increase steadily with the increase in rotor speed from 666.66 rps to 833.33 rps. When the rotor speed is increased, the rate of sliver feed on the machine also increases, which, in tum, causes a decrease in points per fibre, resulting in poor fibre opening'2. In regard to drawframe passages and opening roller speed , the yarn imperfections, particularly neps , follow a similar trend as yarn irregularity because the neps are mainly influenced by the degree of fibre opening and separation.

100.00" 116.66" 83.33" 100.00" 116.66"

4 7 48 30 43 5 9 50 42 47 6 10 42 31 39 7 12 43 33 40 2 6 44 32 38 3 6 46 35 37 4 9 35 28 31 6 11 35 30 33 7 9 58 49 55 8 10 60 54 57 9 12 54 43 48 11 14 56 45 51 4 8 51 43 46 5 10 54 44 49 7 10 45 37 38 9 11 49 42 47

4 Conclusions 4.1 Finer fibres offer significant advantage in rotor

spinning in regard to yarn quality. Both rotor and opening roller speeds have a marked influence on tensile properties. With the increase in opening roller speed, the tenacity, breaking extension, work of rupture and abrasion resistance improve initially but deteriorate thereafter as the opening roller speed is further increased. Higher rotor speed also results in considerable deterioration in these properties. The deterioration in properties at higher rotor and opening roller speeds is more marked in yarns produced with once-drawn sliver.

4.2 The sliver preparation as well as the opening roller speed markedly influence the twist efficiency, which tends to increase with the increase in opening roller speed and drawframe passages. Twist efficiency also increases significantly with the decrease in fibre linear density and rotor speed.

4.3 The use of either too low or too high opening roller speed substantially increases the mass irregularity and imperfections. Higher rotor speed also has deleterious influence on yarn regularity and imperfections. However, the yarns spun from twice­drawn sliver are more regular and have fewer imperfections than their once-drawn counterparts.

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