Physical properties of textile fibres

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Fibre length

In physical properties the most important is the fibre length on which the quality of yarns depends. For cotton if fibre length increases the quality of yarns will be good, but this is just opposite for wool. In jute the fibre length is too long that sometimes the fibres are cut into small pieces.

If the fibre length is too small it is difficult to produce yarn. Yarn is impossible if the fibre length is less than 0.5 inch. Thin fibres produce thin yarn and coarse yarn is produced from coarse fibres.
There are two types of fibre on the basis of length:

1. Continuous filament
2. Staple fibre.

Continuous filament

Long and continuous fibres are called filament. Filaments are continuous in length which can be used as such form or cut into shorter  staple fibre form. These fibre is collected from both natural and artificial source. Any natural fibre can be made into a filament. When only one filament is used in a yarn then it is called monofilament. When more than one filaments are used in yarn then it is called multifilament.

Monofilament → 1.5 holes in spinneret.

Multifilament → 10-100 holes.

Staple fibre

When the length of fibre is short then it is called staple fibre. Stable fibres are manly shorter in length and related to natural fibre. All natural fibres without silk can be collected as staple fibre. Artificial fibres also collected as staple fibre.

Staple fibres are three types on the basis of length:

1. Short staple : Length is less than 2 inch.
2. Medium staple : Length is from 2-4 inch.
3. Long staple : Length is more than 4 inch. 

Strength

The capacity of a fibre to support a load is known as fibre strength. The strength is described as tenacity.

Tenacity = Strength/ linear density.

It is expressed as CN/Tex or N/Tex. The tensile strength is commonly described as the force required to reach break the increase in the length before breaking is known as extension.

Elasticity

It is the property to recover from deformation. The fibre may be elastic or plastic which depends upon fibre condition and surrounding environment.

Flexibility

Flexibility is that property to resist repeated bending and folding.

Cohesiveness

It is the ability of the fibres to cling together during spinning depends on crimp and twist. In natural fibre the property comes from nature but in artificial fibre this property is given by crimping.

Fineness

The term fineness describs the quality of a fibre. By this, we know how fine a fibre is. It is expressed by the terms count, tex, denier, tex per unit length etc.

1 Tex = 1 gm/1000m.

1 denier = wt. in gm/900m.

Fineness affects some fibre properties. Such as yarn count, yarn strength, yarn regularity etc.

Cross section

The cross section of a fibre determines the physical properties of fibre. It gives idea about strength, fineness that varies from fibre to fibre. The cross section shape of a fibre is important because it contributes to the surface appearance of the fibre. It helps to give properties of luster, bulk and body of the fibres, yarn and fabrics. It has effect in twisting, bending or shunning.

Crimp

It refers to the waves or bends that take place along the length of a fibre. It increases cohesiveness and resilience, resistance to abortion and gives increased bulk or warmth to fabrics. It also helps fabrics to maintain their softness or thickness, increase absorbency and show contact comforts bid reduces lusture. A fibre may have one of the three types of crimp. Namely – Mechanical crimp, natural crimp or Inherent crimp and Chemical crimp.

Resiliency

It is the property fo a fibre, which enables it to recover from certain load or stretch over a period of time.

Toughness

The ability of a fibre to endure large permanent deformations without rupture is called toughness.

Work of rupture

The area below the stress –strain curves provides a measure of the work required to break the fibre. It is called work of rupture and it commonly expressed in CN/Tex.

Appearance

It is expressed by length, fineness, cross-section cleanness and lusture of a fabric. Generally short fibres are bulky and loss lustrous.

Density

The density indicates the mass per unit volume. The specific gravity of a fibre indicates the density relative to that of water at 4 degree Calcius.

Elongation

It is the ability to be stretched, extended or lengthened. Elongation vary at different temperatures and when wet or dry.