Essential properties of textile fibre

As discussed previously, until about 100 years ago, all the fibres employed by man were from natural sources. Of all the natural fibres, only a few like wool, cotton, silk, and linen have been very popular for textile purposes. This popularity can be attributed to some of the properties exhibited by these fibres. These properties can be divided into two groups (1) Primary properties or essential properties, responsible for the popularity. There are

five primary properties:

1. Staple (Length)

2. Strength

3. Elasticity

4. Uniformity and

5. spinning quality.

(2) Secondary properties, which are desirable but not essential

Staple (Length)

Length Staple length is used to express the dimension i.e., length only. The fibre must be long and fine This is basically because the two most important fibres c., cotton and wool are available with a definite length and fineness. The length varies in cotton fibre from 1.5 cm to 4 cm and in wool from 3 cm to 40 cm. Further, for blending, man-made filaments are cut into short lengths (staple fibre). This staple length should match with the length of other component fibres, used in blending. In general, in a particular fibre, the longer the fibre, the stronger and finer the yarn. Similarly fine fibres are more useful for soft, smooth and uniform fabrics. For coarse fibres, i.e... higher diameter fibres, the fabric will be coarse and rough.

Strength

The fabric must be durable enough. For durability, the fabric must be strong enough. The strength of the fabric is more influenced by the strength of the fibre present in the fabric. Also, strong fibres can withstand the tension for their conversion into yarn and then into fabric. The strength indicates the resistance sustained by the fibres, the yarns or the

fabrics to break, when force is applied on them. The strength may be tensile strength, bending strength, bursting strength etc as per the direction of application of force.

Elasticity

The third essential property of textile fibres is elasticity. Elasticity is the property indicating the ability of the material to regain its original shape after being deformed by the application of force. The desirable feature of any type of fabric is that the fabric must not distort its shape, during its application. This indicates that the material should have a high elasticity. Higher elasticity indicates higher recovery from deformation. For example, 1000 cm of yarn is stretched to 1050 cm after applying some load to it. After the load is removed, if the fibre measures 1000 cm, then it can be said that the fibre has an elastic recovery of 100 %. But if the length after removal of the load is 1010 cm, then the elastic recovery is 80 % . But in this case, the yarn is elongated to 1010 cm and the elongation is 1%. So it can be said that elasticity opposes elongation. Elasticity or elastic recovery is generally influenced by the extent of stretch, time during which material is kept in its stretched condition and time to recover.

Uniformity

Uniformity of the staple is the fourth essential property. There must be limited variations in length and diameter between fibre to fibre. In other words, the fibre should be more uniform which will ensure uniformity in the yarn as well as in the fabric.

Spinnability

Spinnability is the fifth essential property. It indicates that the individual fibres must be capable of being spun into a yarn and then a piece of fabric with sufficient strength. For better spinnability, the fibre must have better cohesiveness

Interestingly, the 'spinnability' term is commonly used in the case of man-made fibre manufacturing processes. It indicates whether a continuous thread can be produced from a viscous material by extrusion and whether it can be hardened. So a fluid is spinnable under a given deformation condition if steady-state continuous elongation of the fluid jet proceeds without a break of any kind. Technically, the higher the thread length produced, the better the spinnability of the material. These above properties were termed primary properties, which are the most common properties of popular natural fibres. After the introduction of

the man-made fibres, more particularly synthetic fibres, properties the man-made no longer have much importance as all these properties can be induced in the fibre. At present, primary properties or fibre characteristics include the chemical composition, molecular structure, fibre length and fineness.