Influence of moisture content and linear density of feed s liver o n running per formance and yarn quality during rotor spinning of dyed cotton

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1 Indian Journal of Fibre & Textile Research Vol. 28, June 2003, pp Influence of moisture content and linear density of feed s liver o n running per formance and yarn quality during rotor spinning of dyed cotton S M Ishtiaque Departmenl of Textile Technology, I ndian Institute of Technology, New Delhi India and A Das " Northern India Textile Research Association, Sector 23, Raj Nagar, Ghaziabad I ndia Received 4 December revised received and accepted 2 7 February 2002 The effects of moisture content and li near density of feed sliver on rotor spinning performance and yarn qual ity of grey and dyed cotton have been studied. I t is observed that the high moisture content i n the feed sli ver decreases the end breakage rate of grey cotton, but for dyed cotton the running performance deteriorates with the i ncrease in moisture content. With the increase in the l inear density of feed sliver, the end-breakage rate increases for both grey and dyed cotton. The yarn quality in terms of esp, irregularity and i mperfections, in general, deteriorates with the increase in moisture content and linear density of feed sli ver for both grey and dyed cotton. The cotton dyed with natural indigo shows poor running performance and yarn quality in comparison to grey and reactive black dyed cotton. For all the samples, a heavier sliver with high level of moisture content produces poor quality of yarn. Keywords: End-breakage rate, Feed sliver, Linear density, Yarn esp, Yarn imperfections, Yarn i rregularity 1 I ntroduction Rotor spinning performance is mainly affected by machine parameters, fibre parameters and ambient conditions l. 3. Among the ambient conditions, the relative humidi ty and temperature of the spinning section are very important, especially for cotton fibre since it is hygroscopic in nature. The effect of relative humidity and moisture content in feed sliver on rotor spinning stability and yarn properties of grey fibres has been studied i n detaii 4.9. However, no study has been reported on dyed cotton in this 7 respect. Nield and Ali4. carried out significant work on effect of humidity on open-end spinning. They reported the changes in yarn properties and fibre arrangement in the yarn with the change i n relative humidity during spinning. They also studied the effects of conditioning of fibres at spinning point on the properties of yarn. Artzt etalr investigated the running performance and yarn quality during rotor spinning by comparing conventional conditioning, "To whom all the correspondence should be addressed. Present address: Department of Textile Technology, Indian Institute of Technology, New Delhi , India. Phone: ; Fax: ; apurba_das@ hotmail.com spinning zone conditioning and material conditioning for grey cotton and polyester fibre. In another study, Basal and Rust9 i nvestigated the effect of feed sliver moisture content on rotor spinning performance and rotor-spun yarn properties of grey cotton at laboratory scale. They have reported their findings with a limited number of trials using ( i ) high moisture content and high opening roller speed, (ii) high moi sture content and low openi ng roller speed, ( i i i ) low moisture content and high openi ng rol ler speed, and (iv) low moisture content and low open ing roller speed. Their results indicate that the high moisture content decreases the number of ends down, but increases yarn unevenness and imperfections. H igher moisture content of cotton results in higher fibre strength, breaking elongation, fibre-to-fibre friction and lower torsional and bending rigidi t/ o Singh et a t. 1 studied the effect of opening roller speed and linear density of feed sliver on properties of polyester/cotton blended yarn. They carried out their study on a very small scale with a fabricated experimental single rotor OE unit with provisions of individual speed controls on rotor, feed roller, opening roller and yarn take-up unit. However, there

2 178 INDIAN J. FIBRE TEXT. RES.. JUNE 2003 IS no information available on the effect of sliver linear density on running performance and yarn quality of dyed cotton in actual industrial running condition. In the present work, the effects of moisture content and linear density of feed sliver on rotor spinning running performance and physical properties of grey and fibre-dyed cotton rotor yarns have been studied. The cotton fi bres were dyed separately with reactive and natural dyes before spinning and the studies were conducted in an industry on a large scale. 2 Materials and Methods A medium-grade Indian cotton was used in the study. The grey cotton fibres were first opened in a bale breaker and then opened and cleaned with the help of a step cleaner before dyeing. The cotton fibres were dyed with reactive black and natural indigo. The [>roperties of grey and dyed cotton feed slivers are given in Table l. The cotton fibres were processed through blow room, carding and two passages of draw frame. The finisher draw frame slivers were conditioned to have different levels of moisture content before being fed to the OE spinning machine (M 211 Model). The rotor speed, rotor diameter and opening roller speed were kept at 50,000 rpm, 45 nun and 7500 rpm respectively for all the samples. All the conditioned finisher draw frame slivers were used to prepare yarns of 59 tex with 5.0 TM. Pin type opening rollers were used for preparation of all the samples. For all three types of cotton (grey, reacti ve black dyed and natural indigo dyed), three different linear densities of feed sliver, each with three levels of moisture content, were used in the present study (Tables 2-4). The statistical analysis shows that the present study is reproducible. 2.1 Conditioning of the Feed Sliver The finisher draw frame slivers were conditioned to different levels of moisture content before being fed to the OE rotor spinning machine. The slivers were conditioned for medium level of moisture content in a conditioning room with approximately 60±4% RH. The finisher draw frame slivers were removed from the cans very carefully and kept on the floor of the conditioning room in open condition for 72 h to have moisture equilibrium 9. The total material from each can was divided into several small parts so that each part contained about 3-4 kg of sliver. This Table 1- Properties of grey and dyed cotton fibres at finisher draw frame sliver stage Fibre type 2.5% Span Bundle Fibre Residual Crock fastness Fibre-to-fibre length strength fineness trash content frictional mm g/tex Ilglin % Dry Wet coefficient at 40 g normal load Grey collon Reactive black dyed colton Natural indigo dyed colton Table 2 - Effect of moisture content and linear density of feed sliver on rotor spinning performance and yarn quality of grey colton Feed sliver lin- Feed sliver mois- Feed sliver mois- End- breakage Yarn quality ear density ture level lure content rate CSP Irregularity Imperfections/1000 m ktex % breaks/100 rotorslh Thin Thick Neps 4.54 Low Medium High Low M.!!dium High Low Medium High

3 ISHTIAQUE & DAS: ROTOR SPINNING OF DYED COTTON 179 Table 3 - Effect of moisture content and linear density of feed sliver on running performance and yarn quality of reactive black dyed cotton Feed sliver lin- Feed sliver mois- Feed sliver mois- End-breakage Yarn quality ear density lure level ture content rate CSP Irregularity Imperfections/WOO m ktex % breakslloo rotorslh Thin Thick Neps 4.54 Low Medium High Low I 53 Medium High Low Medium I High Table 4 - Effect of moisture content and linear density of feed sliver on running performance and yarn quality of natural indigo dyed cotton Feed sliver Feed sliver Feed sliver End- breakage Yarn quality linear density moisture level moisture content rate ktex % breakslloo CSP Irregularity Im rfections/l 000 m rotors/h Thin Thick Neps 4.54 Low 6.18 Medium 8.79 High Low 6.21 Medium 8.77 High Low 6.20 Medium 8.81 High was done to ensure conditioning of the slivers evenly. For high level of moisture content in feed sliver, the same procedure was followed but the relative humidity of the conditioning chamber was increased to approximately 87±4%. To have low level of moisture content, the finisher draw frame slivers were partially dried in a fibre dryer so that some amount of moisture evaporates out from the fibre. The slivers after proper conditioning at different levels of moisture content were immediately put into the cans and the top portions of the cans were closed with polythene sheet to prevent any moisture transmission. The moisture content of the slivers within the cans was measured intermittently at an interval of 30 min and no significant changes in the moisture content were observed during spinning. For each sample, thirty such cans were prepared. The cans were then brought to the open-end spinning machine immediately. A small hole in the polythene covers at the centre of each can was made to facilitate the proper withdrawal of the sliver without much change in the moisture level of the sliver. 2.2 Study on Running Performance The rotors were cleaned properly and the yams were pieced and allowed to run. Three sections of the machine, i.e. thirty rotors, were selected for the present study. The running performance was assessed by the end-breakage rate, which was measured on thirty rotors after one hour of running and the

4 180 INDIAN J. FIBRE TEXT. RES., JUNE 2003 averages of four such studies were taken. At the time of end breakage and also at the end of the study, the condition of the rotors was observed visually. The end-breakage rates for all the samples are given in Tables Measurement of Fibre and Yarn Properties The fibre length, bundle strength and micronaire of grey and dyed cotton were measured at finisher draw frame stage by Uster HVI. The residual trash content of finisher draw frame sliver was measured in a trash analyser. Dry and wet crock fastness was measured in a crock meter. Fibre-to-fibre frictional coefficient was measured with the help of an attachment fitted with SOL tensile tester. Fibre parameters of all the samples are given in Table I. The moisture content of the feed sliver was measured with the help of IR moisture balance. All the thirty cheeses were taken for testing of the yarn properties for each sample. The CSP of the yarn was measured in a lea strength tester. The irregularity and imperfections of all the yarns were tested in Keisokki evenness tester at a speed of 400 m/min for 2.5 min. The number of thin places, thick places and neps per 1000 m were measured at -50%, +50% and +280% levels. The details of test results are given in Tables Results and Discussion 3.1 ElTect on Running Performance It is clear from Tables 2-4 that the end-breakage rate is highest for natural indigo dyed cotton, followed by reactive black dyed cotton and grey cotton for all the levels of feed sliver linear density and moisture content. Table 2 shows that for grey cotton there is no significant change in end-breakage rate when the level of moisture content is increased from low to medium. But further increase in moisture level of feed sliver results in significant improvement in running performance. The same trend is observed at different linear densities of feed sliver. The decreased number of end breakages at high moisture content may be due to the increase in cotton fibre strength, coefficient of friction between fibres and fibre elasticity. Basal and Rust 9 also observed the similar trend. For natural indigo dyed cotton, as the moisture content of feed sliver increases the end-breakage rate increases significantly at all levels (Table 4). Ai high level of moisture content, the end-breakage rate becomes very high. Although the increase in moisture level in sliver increases the fibre strength and fibre elasticity, but at the same time it changes the characteristics of inner rotor surface when spinning dyed fibres with poor crock fastness properties ' 4. During spinning, the indigo dye was transferred from fibre to the inner surface of rotor, which was due to the poor crock fastness of natural indigo as shown in Table 1. As the wet crock fastness is very poor for natural indigo, more dye particles are expected to transfer to inner surface of rotor at higher level of moisture content of feed sliver which results further deterioration in running performance. The end-breakage rate of reactive black dyed cotton (Table 3) also shows an increase with the increase in moisture content, but the change is not significant for lighter feed sliver. The reactive black dyed cotton has got moderate wet crock fastness and good dry crock fastness. As the moisture level increases in the sliver, it is expected that there will be some dye deposition on the rotor surface at higher level of moisture content, which causes changes in surface characteristics of rotor and more end breakage. For the lighter feed slivers, better individualization of fibres may have neutralized the deteriorating effect of higher moisture level, resulting in consistent running performance with the increase in moisture content. Tables 2 and 3 show that as the weight of feed sliver increases from 4.54 ktex to 5.37 ktex, the endbreakage rate remains almost unchanged for grey and reactive dyed cotton at all the levels of moisture content, but for natural indigo dyed cotton (Table 4) it increases with the similar increase in feed sliver weight at low and medium levels of moisture content. This may be due to the higher coefficient of friction in indigo dyed cotton; improper individualization of fibres was there for heavier sliver which resulted disturbance in rotor groove, causing higher endbreakage rate. When the sliver weight is increased further to 6.56 ktex, the end-breakage rate increases significantly for all the samples (Tables 2-4). In case of indigo dyed cotton, at high level of moisture content the end-breakage rate remains almost unchanged with the increase in feed sliver linear density. This indicates that the effect of transfer of dye particles to rotor surface, which changes the surface characteristics of inner rotor wall at higher level of moisture content, dominates over the effect of improper fibre individualization due to the heavier feed sliver in case of natural indigo dyed cotton.

5 ISHTIAQUE & DAS: ROTOR SPINNING OF DYED COTTON 3.2 Effect on Yarn Quality Tables 2, 3 and 4 show the quality of yarns at different levels of moisture content and feed sliver linear density for grey, reactive black dyed and natural indigo dyed cotton respectively. It is clear from these tables that the yarns made from grey cotton are having highest esp and least irregularity at all the levels of moisture content. For natural indigo dyed cotton, the esp is lowest and irregularity is highest for almost all the levels of moisture content. The reactive black dyed cotton yarn shows intermediate properties in terms of esp, irregularity and imperfections. The poor quality of yarn in case of natural indigo dyed cotton may be due to the change in surface characteristics of rotor wall and also due to the improper individualization of fibres due to the higher fibre-to-fibre coefficient of friction. Tables 2-4 also show that with the increase in mois ture content of feed sliver the yam quality in terms of esp, irregularity and total imperfections deteriorates in all the samples except for lighter weight feed slivers of grey and reactive black dyed cotton. The deterioration in yarn quality with the increase in moisture content may be due to the fact that higher moisture content in feed sliver causes poor fibre individualization during opening and improper orientation of fibres inside the rotor groove due to the increase in fibre-to-fibre fric tion coefficient and fibre swelling9. It is evident from Tables 2-4 that as the feed sliver linear density increases, the yarn esp, irregularity and total imperfections deteriorate for all the samples at almost all the levels of moisture content. The similar trend was also observed by earlier workers l 3 for yarn strength, but in case of yarn irregularity (), they reported the reverse trend. The decrease in yam irregularity with the increase in the linear density of feed sliver was in fact due to the doubling effects of the sliver in their experiment. To increase the linear density, they used more than one sliver in the feed zone. But in the present study, the deterioration in yam quality may be attributed to the improper individualization of fibres at heavier sliver feed. For grey and reactive black dyed cotton with lighter feed sliver (4.54 ktex) the yarn irregularity and total imperfections are found to be comparatively high at the lowest level of moisture content (Tables 2 and 3). This may be due to the fact that in case of lighter and dry grey and reactive black dyed cotton the lower inter-fibre cohesion results in poor fibre control during opening, individualization and transport. On 181 the other hand, in case of natural indigo dyed cotton, the best result is achieved at low level of moisture content with l ighter (4.54 ktex) feed sliver (Table 4). 4 Conclusions Running performance during OE rotor spinning improves at high level of moisture content in feed sliver for grey cotton. For dyed cotton, it deteriorates with the increase in moisture content and maximum deterioration is observed in case of natural indigo dyed cotton where wet crock fastness is very poor. 4.2 With the increase in feed sliver linear density, the running performance in general deteriorates. 4.3 The end-breakage rate in case of natural indigo dyed cotton with high level of moisture content remains almost unchanged with the increase in weight of feed sliver. 4.4 The yarn quality in terms of esp, irregularity and imperfections deteriorates with the increase in moisture content and linear density of feed sliver for all the samples. 4.5 The natural indigo dyed cotton with higher fibre to-fibre coefficient of friction and lower dry and wet crock fastness produces worst quality of yarn with heavier feed sliver having high level of moisture content. 4.1 References I Trommer G, Rotor Spinning (Deutscher Fachverlang, Frank furt/main, Germany), Barell a A, Manich A M, Marino P N & Garofalo J, J Text Inst, 74 ( 1 983) Humidification, ventilation and lighting, Colourage, 39(6) ( 1 992) Nield R & Ali A R A..J Text Illst, 68 ( 1 977) Nield R & A l i A R A, J Text Inst, 6 8 ( 1 977) Nield R & Ali A R A, J Text Inst, 68 ( 1 977) Nield R & Ali A R A, J Text Inst, 68 ( 1 977) Artzt P, Herter T & Preininger H, Int Text Bull, Yam Foml ing, 36(3) ( 1 990) 4. 9 Basal G & Rust J P, Text Res J, 71 (200 1 ) Nakamura K, Hatakeyama T & Hatakeyama H, Text Res J, 53 ( 1 983) 682. I I Gulllti A N, The Physical Properties of Cotton (Asia Publish ing House, Bombay, India), Hearle J W S & Peters R H, Moisture in Textiles (Textile Book Publishers, Inc., New York), Singh V P, Grosberg P & Oxenham W, Influence of opening roller speed on rotor-spun polyesterlcotton yam quality and spinning stability, paper presented at the Seminar on Rotor Spinning,. Indian Institute of Technology, Delhi, September Ishtiaque S M & Das A, Indian J Fibre Text Res, 27 (4) (2002)