HAIRINESS IN YARN
I am very happy to add this article written by Mr.Kamatchi Sundaram , All india Service Manager of VOLTAS LTD. INDIA, in my site. He is one among the good technologists who has indepth knowledge about textile technology and spinning machines. I hope this information is of use to the technical people who browse through this site.
Hairiness is a measure of the amount of fibres protruding from the structure of the yarn. In the past, hairiness was not considered so important. But with the advent of high-speed looms and knitting machines, the hairiness has become a very important parameter.
In general, yarn spun with Indian cotton show high level of hairiness due to the following reasons.
1. High short fibre content in mixing.
2. Low uniformity ratio.
3. High spindle speeds.
Hence most of the Indian yarns have a hairiness index above 50% Uster standards. However, as this parameter is becoming more and more important, Indian spinners are concentrating more on this aspect and try to reach at least 25% standards by conducting lot of trials. He has conducted a lot of such studies on hairiness and he is pleased to share his learning’s with you.
Hairiness is measured in two different methods.
1. USTER HAIRINESS INDEX:
This is the common method followed in India. The hairiness index H corresponds to the total length of protruding fibres within the measurement field of 1cm length of the yarn.
2. ZWEIGLE HAIRINESS INDEX:
This zweigle hairiness measurement (S3) gives the number of protruding fibres more than 3 mm in length in a measurement length of one meter of the yarn.
From the above you can infer that Uster hairiness index give the total length of hairs whereas zweigle hairiness testers give the absolute number of fibres. Though the later measurement is more accurate, most of the Indian spinners are still following Uster hairiness index only.
The factors effecting hairiness can be sub divided into 3 major components.
a) The fibre properties.
b) Yarn parameters.
c) Process parameters.
a)THE FIBRE PROPERTIES:
Fibre length, Uniformity ratio, Micronaire and short fibre content are the properties exerting high influence on hairiness. Among the above the length and short fibre content exerting major influence. For a particular count, higher length of fibre leads to lesser hairiness and high short fibre content leads to high hairiness.
Hairiness is dependent on the number of fibres present in the cross section of the yarn. Hence coarser yanrs have more hairiness compared to finer yarns.
The yarn twist is another major factor and higher twists lead to less hairiness up to a certain extent. This is the main reason while hosiery yarns normally have high hairiness compared to warp yarns.
However in a mill condition, the fibre parameters and yarn parameters cannot be adjusted. Hence the next topic, process parameters, assumes very high significance, as this is the only available option at the mill level to reduce the hairiness.
C) PROCESS PARAMETER:
The preparatory machines do not have a big influence on hairiness. The Speed frame, Ring frame and the Cone winder are the only machines to be attended for reduction in hairiness. I give below the various process parameters that can be attended for reducing the hairiness.
1. Roving hank: It plays a major role in the reduction of hairiness. For a particular count, the hairiness of the yarn goes down, as the roving hank is made finer and finer.
For example: If 30s yarn is spun with 0.8 and 1.0 hank, yarn made with 1.0 hank will give lesser hairiness than the yarn made with the 0.8 hank. Hence please conduct a trial with finer roving hank to reduce the hairiness. The results of the study conducted recently at a leading mill are given below for your reference on this point.
TRIALS ON HAIRINESS
EFFECT OF ROVING HANK ON HAIRINESS
|Ring rail bottom po||
Ring rail top postion
|COUNT||24 ch||24 ch||24 ch||24 ch||24 ch||24 ch|
You would note from the above that the hairiness as well as imperfections have improved significantly by using finer hank of the roving.
2. Spacer Size: It is the normal tendency of the technicians to use spacer as thin as possible to reduce the U% and imperfections. But thinner spacers lead to higher hairiness. Hence please conduct a trial with a spacer, which is 1.0 to 1.5 mm thicker than existing spacer.
b) RING FRAME:
1. Ring Traveller: It is generally opined by many technicians that the traveller plays a major role in hairiness. Though selection of the traveller plays a small role in hairiness (specially with reference to the yarn clearance), it’s effect is quite less. This is because the yarn contact point with the traveller is quite far away from the ring and traveller contact point. Hence even if the traveller is run for a long time, the hairiness will not increase. But the breakage rate will increase.
2. Ring: It is the general opinion of some technicians that imported rings give lesser hairiness than Indian rings. It is also believed by technicians that older rings give more hairiness. Recent studies / trials conducted by us recently at a leading mill indicate this not to be true. Please refer the table below.
EFFECT OF RINGS ON HAIRINESS
RING COPS TRAIL (TOP POSITION OF THE RING RAIL)
|PARAMETERS||old lmw rings||new lmw rings||bracker rings|
|NOMINAL COUNT||30s CH||30s CH||30s CH|
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