and Coating on Hairiness of Acrylic Yarns

 Introduction

Hairiness significantly influences the properties of yarns and fabrics. Hairiness in warp yarns can cause considerable breakage and hence stoppage of weaving looms, thus reducing the efficiency of production. It causes pilling on fabrics, resulting in poor appearance. Yarn hairiness is very complex, but this parameter is now as routinely tested as the other parameters of yarns. Hairiness can be defined as the state of migrated fibre ends and fibre loops pushed to the surface of the yarn body. The factors causing yarn hairiness can be studied in three different ways; the physical properties of fibres, yarn parameters and machine parameters used.

Several investigations have been carried out on the influence of the ring traveller. In some studies, it was observed that yarn hairiness decreased as the weight of the traveller increased, whereas in some others it was stated that as the traveller weight is increased the hairiness gradually decreased to a certain point, then started to increase [1-5].

Experimental

Table 3. Values of yarn properties.

measurements from the 4 coated types of travellers was insignificant, their average values were taken for ‘coated’ in general as tabulated in Table 4.

It is seen in the table that when using the C2f type ring travellers, yarn hairiness was caused (in order of importance) by fibre bridges, short fibres, long fibres, fibre loops, vertical fibres and loose fibres. With the M2f type ring travellers, the order was short fibres, fibre bridges, long fibres, vertical fibres, fibre loops and loose fibres. With the M2dr type ring travellers, the order becomes fibre bridges, short fibres, long fibres, loose fibres, vertical fibres and lastly fibre loops. According to these results, fibre bridges and short fibres are found as the major forms of fibres which cause hairiness in the acrylic yarns tested.

Pilling assessment on the fabric knitted

To determine the effect of hairiness on the pilling of fabrics, the yarns spun at 10,000 rpm were used for knitting a stocking fabric using a Bentley Comet machine of 4", E 14, 160 needles. The knitted fabric samples were stored in laboratory conditions for 48 h. The samples (4 samples related to each ring traveller type) were tested on a Nu-Martindale fabric abrasion and pilling tester. Testing circles were exposed to 1000 rubs, and the assessment made according to Empa Standards [11]. The results of the measurement were compared with the K2 Empa standard photographs in the order of 1-2, 2-3, 34 and 4-5 from worst to best. The results are presented in Table 5.

FIBRES & TEXTILES in Eastern Europe October/December 2002

Figure 1. Photos taken by the SEM; a - short fibres; b - long fibres; c - fibre bridges; d - fibre loops; e - loose fibres; f - vertical fibres.

Determination of yarn tension

Yarn tensions determined during the spinning process were measured with the ring rail at the bottom position

Figure 2. Areas of protruding fibres; a - region of long fibres; b - region of short fibres; c - assumed yarn body.

Table 4. Numbers of fibres counted (No/m).

when the tension value was at maximum. A Schmid 2F2 tester was used for yarn testing between 10-100 cN. According to the well-known dependency, the yarn tension increased as the spindle speed and/or traveller weight increased (Table 6).

Results and Discussion

The results of the experiment clearly showed that the ring traveller weight had a significant influence on yarn hairiness, and that the character of this influence depends on the traveller type, coating and spindle speed. In general, for all experiments discussed the yarn hairiness decreased as the weight of the travellers increased. However, local maxima of the particular dependencies can be observed in Figure 3. Using C2f type travellers at 7000 rpm spindle speed, there were no significant changes in the results with respect to different coatings of the same type, but nevertheless it seemed that the best results were obtained from the Silvernic type travellers (Figure 3a).

With M2f type travellers at the same spindle speed of 7000 rpm, yarn hairiness became considerably lower (Figure 3b), especially with weights above 85 mg for the Silvernic coated traveller. With M2dr type travellers, the smallest hairiness was with the traveller of micronic type up to the weight of 95 mg. However above the weight of 95 mg, the Silvernic coated traveller produced lower hairiness than any other traveller type (Figure 3c). Running at 10,000 rpm spindle speed with C2f type travellers, the lowest values of hairiness were determined on yarns produced using C2fSP type ring travellers (Figure 3d). At a spindle speed of 10,000 rpm

_{Statistical Analysis}

 the travellers, coating type and yarn the best, as they produced considerably tension to estimate their effect on yarn less hairy yarns when compared with hairiness. The tests of significance the others (Figure 3f). were made at 95% and 99% confidence of travellers has a significant effect on yarn hairiness for all travellers analysed and at both spindle speeds. Regarding coatings, a significant effect can be observed only for M2dr at 7000 rpm and C2f at 10,000 rpm. Yarn tension also plays an important role in yarn hairiness, as can be seen from Table 8. The results in Table 8 shows the significant effect on yarn hairiness by spinning tension caused by traveller weight. The results with coated travellers were significant, except for C2f at both spindle speeds and M2f at 10,000 rpm.

cant influence on reducing the yarn hairiness.

• Microscopic observations confirm the Shirley Yarn Hairiness test results.
• The flat types of M2f and C2f travellers caused less hairiness than the M2dr half-round type travellers.
• It is generally accepted that yarn hairiness increased as the spindle speed is increased [12]; however, this observation appeared as only partly true in our investigation. Spinning with light weight travellers, the yarn hairiness increased regularly as the spindle speed increased; but spinning with heavy travellers, the results became irregular, e.g. higher hairiness was measured at the spindle speed of 7000 rpm than when spinning at 10,000 rpm.
• Yarn hairiness is reflected in pilling of the fabric produced. Consequently, as traveller weight increases, pilling of the fabrics generally decreased. It should be stressed that the fabrics did not show any pilling when yarns had been spun with C2f and M2f travellers of 106, 112 and 125 mg weight.
• We propose that the travellers of two counts heavier than the manufacturers’ specification must be utilised in spinning to produce less hairy yarns.
• In acrylic spinning, the use of M2f and C2f travellers can be preferred regarding the avoidance of hairiness in yarn, provided that they are not objectionable for other reasons.

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