YARN HAIRINESS - 2
Hairiness Testing of Yarns
Hairiness of yarns has been discussed for many years, but it always remained a fuzzy subject. With the advent of compact yarns and their low hairiness compared to conventional yarns, the issue of measuring hairiness and the proper interpretation of the values has become important again. Generally speaking, long hairs are undesirable, while short hairs are desirable (see picture ). The picture shown below just give a visual impression of undesirable and desirable hairiness at the edge of a cops.
RING YARN COMPACT YARN
There are two major manufacturers of hairiness testing equipment on the market,and both have their advantages and disadvantages. Some detail is given below.
USTER is the leading manufacturer of textile testing equipment. The USTER hairiness H is defined as follows .
H =total length (measured in centimeters) of all the hairs within one centimeter of yarn .
(The hairiness value given by the tester at the end of the test is the average of all these values measured, that is,if 400 m have been measured,it is the average of 40,000 individual values) . The hairiness H is an average value,giving no indication of the distribution of the length of the hairs. Let us see an example
Both yarns would have the same hairiness index H, even though yarn is more desirable,as it has more short hairs and less long hairs,compared to yarn 2.
This example shows that the hairiness H suppresses information,as all averages do. Two yarns with a similar value H might have vastly different distributions of the length of the individual hairs.
The equipment allows to evaluate the variation of the value H along the length of the yarn. The "sh value "is given, but the correlation to the CV of hairiness is somehow not obvious.A spectrogram may be obtained.
Zweigle is a somewhat less well known manufacturer of yarn testing equipment. Unlike USTER,the Zweigle does not give averages. The number of hairs of different lengths are counted separately, and these values are displayed on the equipment. In addition, the S3 value is given,which is defined as follows:
S3 =Sum (number of hairs 3 mm and longer)
In the above example,the yarns would have different S3 values:
S3yarn 1 =2 .
S3yarn 2 =4 .
A clear indication that yarn 2 is "more hairy "than yarn 1. The CV value of hairiness is given a histogram (graphical representation of the distribution of the hairiness) is given.
The USTER H value only gives an average,which is of limited use when analyzing the hairiness of the yarn.The Zweigle testing equipment gives the complete distributionof the different lengths of the hairs. The S3 value distinguishes between long and short hairiness, which is more informative than the H value.
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