Pakistan Textile Journal. October index

Hair Severity: An excellent Yarn Selection Tool
by V.Srinivasan 1& S.Balamurugan2, Premier Evolvics Pvt Ltd, India This is the last of four series article on Hair Severity - A new yarn hairiness parameter introduced by Premier

1Mr. V Srinivasan is a B.Tech (Electronics and Communication) and has been with Premier Evolvics for the last twenty years. As the head of R&D for lab products, he is responsible for the conceptualization, design and ongoing technical support for Premier Lab Products. He is an active member of the ITMF spinners committee and has presented several papers at international forum like Bremen Fibre Conference. He also has 3 patents in his name.

2Mr.S.Balamurugan is a Textile Technologist with more than 18 years of experience. He has worked with leading manufacturers & mills like Super Sales, Precot-Hindupur and Isparta Textiles –Turkey. At Premier Evolvics he has contributed extensively towards development of the Hair Severity parameter. His key area of excellence includes quality and maintenance in spinning.

The undesirable long hairs decide the Fabric appearance as well as the performance in Knitting and Weaving. As the conventional Hairiness measurement is not the true representation of Hairs distribution, Premier has introduced a new parameter called Hair severity (HS) which represents the True hair values.

In the early days, Hairiness values were not given much importance. But with the arrival of High speed weaving and knitting machines, Hairiness has become a very important parameter which highly influences the machine performance. The effect of yarn hairiness in post spinning process such as weaving and knitting and its influence on the characteristics of products obtained and on some fabric faults has led to the introduction of measurement of Hairiness. Distribution of hair length is one of the most important characteristic of the yarn which is a decisive factor for Knitting and Weaving performance.

Hairiness Index is not the true representation of hairs distribution. Hair count distribution from 3 to 10 mm involves a complex procedure to analyze. Since the application of both the above parameters calls for a comprehensive solution, Premier has introduced a new parameter “Hair Severity” in Premier iQ Qualicenter

Importance of monitoring HS towards appearance of Fabric as well as knitting and weaving performance was studied in Circular knitting and Projectile weaving machines.

The primary objective of spinner is to produce and supply yarn with required quality for knitting process.

v How to select an appropriate yarn based on HS for achieving acceptable fabric Quality?

In order to address the above questions, Premier has investigated extensively on various aspects of in circular knitting machine.

Generally knitters have critical criteria for yarn quality which includes, yarn that sheds less, creates less fly in and around the knitting machine, good package, soft feeling etc. Protruding hairs from the yarn surface is the main reason for fly liberation. As far as Knitted fabrics are concerned, Pilling and Barre are the major problems caused by hairiness variation in yarn which deteriorates the fabric Quality.

Pilling is a surface fabric fault comprising of circular accumulations of entangled hairs with fibres around them, causing a more significant default on the fabric surface affecting the appearance and handle of the fabric. The formation of pills occurs due to the mechanical action during wash and wear of the fabric where fibres that protrude from surface entangle causing fuzzy appearance. Yarn Hairiness has been shown to contribute significantly in fabric pilling. The above figure shows a fabric with pilling effect due to high hairiness.

Barre is a “Repetitive visual pattern of continuous bars or strips usually parallel to the yarn direction”. To certain extent yarn Hairiness has been reported to account for the cause of Barre effect in fabrics. This Barre effect shows up more prominently after dyeing which affect the finished fabric appearance.

The performance of knitting machine is mainly affected by Yarn Hairiness which is reflected accurately by Hair severity. The knitting defects which we have discussed above are sometimes identified during the process and some appear after dyeing and finishing. Prevention of the above defects that occur during knitting requires monitoring of Hair severity while selecting the yarn.

With the conventional measurement of Hairiness, degree of protruding hairs is not pronounced. Hair severity significantly contributes towards the performance of knitting machine and fabric quality. Extensive studies have been conducted to study the effect of Hair severity on knitting performance. Basic details of one of the study is given in Table-1.

To conduct this study, yarn was procured from two different sources with identical process parameters. Both the samples were tested for hair severity and the results are shown in Table-2.

It can be inferred from the above table that conventional parameters do not reflect much towards yarn Hairiness as well as associated performance, whereas Hair severity shows a substantial difference in values which reflects in average yarn breaks/h.

While processing Sample ‘A’, high end breaks were noticed. As shown in Fig.1, protruding hairs got liberated and accumulated around the yarn body in a ball form which hinders the yarn passage. Due to high Hair severity resulted by longer hairs, ball formation was quicker and resulted in

In spite of several disadvantages, Hairiness has some benefits, where a certain amount of Hairiness is desirable for specific requirements. The distribution of length of hairs is one of the important characteristics of yarn. To achieve the required fabric properties and quality, short length hairs are desirable whereas long length hairs are undesirable where the hairs on yarn surface creates a fuzzy appearance and also formation of pilling. Hence selection of appropriate yarn is the decisive factor to achieve acceptable fabric quality. To select a yarn, which performs at an optimum level, and also to understand the pilling effect, two samples with different HS were selected. Both the samples were dyed and were tested for the pilling effect. After pilling, the fabric was compared with the appearance grades as shown in the figure.2. Table. 3 shows the result with reference to HS values. Hence by monitoring HS, suitable yarn can be selected to achieve acceptable level of fabric quality and also the machine performance.

It is a well known fact that high speed shuttleless weaving machines with ever increasing fabric density are high sensitive to yarn Hairiness in both warp and weft. Barre effect is se

en mostly in knitted fabrics, although it appears in woven fabrics as unwanted stripes in the weft way. If the yarn hairiness is more, adjoining warp threads cling together in loom shed, which in turn resist the separation of sheet during shedding. Thereby the shed becomes improper and causes interferences during weft insertion. This also leads to more warp breaks and fabric defects. In spite of clinging of fibres, higher warp tension; raises yarn hairiness at the shedding zone and inter yarn abrasion loosens the long raised hairs and starts rolling in the yarn axis increasing ball formation along the yarn surface. These fibre balls not only leads to breaks, also deteriorate the fabric quality and appearance. Apart from inducing more breaks these long length Hairs also create interlacement faults in warp way as well as weft way and create a hazy fabric appearance after dyeing.

To highlight the importance of Hair severity in weaving performance, Premier has conducted trials over extended period in weaving machines. Yarn was procured from two different sources and controlled studies have been carried out in projectile weaving machine. The samples collected were used as warp for bed-linen fabric. Both the samples were processed under identical conditions at warping, sizing and weaving. The details are shown in Table-4.

Both the above samples were tested in Premier iQ Qualicenter and Tensile tester. Results are provided in Table: 5 and 6.

As the RKM is lower in sample A, mills have applied higher level of size pickup by 4% (i.e. 12% for sample B as against 16% for sample A). This has resulted in higher strength improvement after sizing. In spite of that, working performance of sample B is found to be better with yarn having low Hair severity. In sample A, the fact that extra size application has been absorbed by protruding hairs, which didn’t contribute for improving abrasion resistance while working on looms. This has been substantiated by the” Projectile cuts’’ and also the efficiency of looms worked on the Sample A & B (Refer Table: 7).

It was observed that sample B was performing better during the process of Warping, Sizing and at loom shed. Both samples were observed for 100 loom shifts.

Since sample ‘A’ has significantly higher loom breaks, breakage study was conducted to analyze the cause. The outcome of the study is in Table: 8 which revealed that contribution of the projectile cuts were high due to higher HS. Hairiness related fabric faults were also analyzed and found that most of the faults were due to high interlacement faults like Warp stitches and Weft pick over. Apart from this, yarn with high hair severity generates more fly in loom shed which is hazardous to human health and necessitates frequent cleaning. Hence, Premier recommends monitoring of HS during selection of Raw material to optimize the Weaving performance.

From the above studies it is clearly evident that yarn with high hair severity affects the knitting and weaving performance by the way of breaks and fabric quality. Hence necessary care should be taken in selecting the yarn for superior grade knitted fabrics and high density fabrics to achieve better machine efficiency and acceptable level of fabric quality

PREMIER iQ QualiCenter™ helps the user to identify the required yarn quality level for subsequent processes like knitting and weaving through Hair severity. Thus yarn procurement decision is made easy and objective.

The importance of monitoring Hair severity in further processes like Knitting and Weaving, has been revealed through extensive studies. These studies reveal useful information for knitters and weavers in selection of appropriate yarn to keep their quality, productivity and cost levels within standards.

For a detailed understanding of the above, write to Premier at mail@premier-1.com for a copy of the Premier Intelligence Book on Hair Severity.