Yarn Hairiness: Causes, Factors, Measurement and Disadvantages

What is Yarn Hairiness?
Yarn hairiness is defined as hairs protruding from the main body of a yarn. It is the ratio of length of all protruding fiber in 1 cm and the yarn actual length (1 cm). Yarn hairiness is an undesirable property which causes problems in fabric production. It is a unit less parameters. Yarn hairiness, one of the most important yarn parameters, is usually characterized by the amount (number or cumulative length) of fibers protruding out of the compact yarn body. Therefore it is very important to measure the length of hair in order to control it. However, at the same time it is not possible to represent hairiness with a single parameter because the length of hair and number of hairs exceeding 3 mm length as a percentage of the total number of hairs is found to be linearly related to the linear density of yarn.

Hairiness value of the coarser yarns is normally lower than the finer yarn due to good cohesive / frictional forces between the constituent fibers in the coarser yarns.

Hairiness could broadly be classified under three categories, namely leading hairs, trailing hairs and looped hairs. Yarn hairiness has a great influence on the sizing, weaving and knitting processes. Higher hairiness increases the cost of sizing. During the shedding operation in weaving, the hairy yarns often entangle with each other and thus hinder the creation of distinct shed which is essential for the passage of the weft or weft carrier. In case of air-jet weaving, the yarn hairiness favorably influences the air-drag exerted on the yarns. Hairy yarns generate fly during the knitting and obstruct the smooth functioning of the machine parts, including needles. Excessive variation of yarn hairiness may cause a ‘Barre’ effect in the finished fabric. However, yarn hairiness is a necessary evil. Too much hairiness is detrimental for the fabric appearance but a certain amount of hairiness is important to both the textile operations and the appearance of fabrics and garments so that the fabric possesses a softer feel and a warmer hand.

By nature, hairiness in short staple fibre yarns is the reason for wide differences in fiber thickness, maturity, micronaire, uniformity ratio of fibres, spinning conditions, and maintenance of spinning machineries are the key factors which influence the yarn hairiness. In filament yarns, hairiness occurs due to weak monofilaments, inadequate finish, rough surfaces and loose running monofilaments which break during the subsequent processes.

Causes of Yarn Hairiness:

1. Raw material
2. Maturity: In case of cotton 70% maturity of the fibers is needed; if less it then leads to hairiness. Immature and dead fibers result in hairiness.
3. Micronaire (fineness): Range of micronaire value of fiber for cotton yarn is 4.2 ± 0.2. Micronaire value of 4.2 ± 0.6 results in increased hairiness, which is used in soft, flannel-like fabrics.
4. Uniformity ratio: Normally, uniformity ratio of fibers is 40%-50%. If it is less then hairiness occurs.
5. Process: Inadequate drafting and orientation – spinning triangle.
6. Maintenance: Rubbery surfaces, life of devices or machine parts.

Factors Influencing Yarn Hairiness:

a) Fiber-related factors of yarn hairiness:
The following fibre-related factors influence the hairiness of spun yarn significantly:

1. Torsional and flexural rigidities
2. Fiber length and short fiber content
3. Fiber fineness.

b) Process-related factors of yarn hairiness:
The following process-related factors influence the hairiness of spun yarn significantly:

1. Spinning technology
2. Winding operation
3. Blending and mixing
4. Combing operation
5. Number of drawframe passages
6. Roving fineness and twist
7. Yarn twist
8. Spinning draft
9. Spindle speed
10. Traveller weight
11. Spacer size.

Effects of Yarn Hairiness:

• It causes problems in printing.
• Fine designs are difficult to make.
• Machine parts life is reduced.

Disadvantages of Yarn Hairiness:

1. Hairiness lowers the yarn strength.
2. If yarn is fuzzy, size material will not penetrate to the required amount and a greater amount will accumulate on yarn surface, that is, coating is more but penetration is less.
3. In air jet weaving, clear shed is not produced. Similarly if fabric density is more, two adjacent yarns cause problems due to hairiness.
4. The machine parts like drop wires, heald wires and reed get worn out frequently.
5. In knitting, the needles get worn out frequently.

Benefits of Yarn Hairiness:

1. Flannel-type fabrics can be produced
2. Increasing feel softer and warmer to the touch, enhancing the comfort of fabrics
3. Slightly hairy yarn can create a natural, rustic, or matte finish in home decor or casual wear
4. The comfort parameters of textile fabrics (air permeability, moisture vapour transport and thermal properties) depend on yarn hairiness.

Measurement of Yarn Hairiness:
Two parameters are important in the measurement of yam hairiness: the number of hairs in a particular length of yarn; and the length of the hair.

Yarn hairiness is measured by the following instruments or tester:

1. Shirley yarn hairiness tester,
2. Zweigle yarn hairiness tester (Zweigle G565) and
3. Uster yarn hairiness tester

Above testers have been widely used in the textile industry for the assessment of yarn hairiness.

In addition to the traditional methods, digital analysis of high-quality images of a textile yarn can characterize hairiness. In this method, an image of high resolution or a microscope image with an appropriate magnification is usually adopted to ensure the clear presence of yarn hairs in the image.

Shirley Yarn Hairiness Tester:
The Shirley yarn hairiness tester measures yarn hairiness based on an optical principle. The yarn under test is passed between a beam of light rays and the receptor photocell at a constant speed. When a hair passes between the light rays and the receptor, the light rays are momentarily interrupted and an electronic circuit counts the interruption as one hair. The instrument has two sets of yarn guides as shown in Figure 2. The lower set leads the yarn over a guide at a fixed distance of 3 mm from the receptor. The upper set leads the yarn over a movable guide which can be adjusted at a distance of between 1 mm and 10 mm from the receptor. Therefore, testing of hair length can be customized up to a length of 10 mm. The number of hairs counted over a length of 1000 m is reported.

References:

1. Physical Testing of Textiles by B. P. Saville
2. A Practical Guide to Textile Testing By K. Amutha
3. Technical Textile Yarns: Industrial and Medical Applications Edited by R. Alagirusamy and A. Das
4. Textile Engineering – An Introduction Edited by Yasir Nawab
5. Bamboo Fibers: Processing, Properties and Applications By K. Murugesh Babu and S.M. Chandrasekhara
6. Computer Technology for Textiles and Apparel Edited by Jinlian Hu

Mazharul Islam Kiron

Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. Mr. Kiron is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.

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