Study Unit 3.2 Primary Properties

Question 1

Primary properties

Answer 1

In order to be used as a textile fibre, a fibre must possess certain properties. These are known as primary fibre properties, and a fibre that does not possess these primary properties cannot be processed into a yarn or fabric.

Question 2

5 Primary properties

Answer 2

1. Length-to-width ratio
2. Strength
3. Flexibility
4. Spinning quality/cohesiveness
5. Uniformity

Question 3

1. Length-to-width ratio

Answer 3

The fibre must be long enough and the length must be considerably greater than the diameter, ie it must have a high length to width ratio. A minimum ratio of 100 is considered essential, but most fibres have much higher ratios.

Question 4

2. Strength

Answer 4

A fibre with a length to width ratio of 100:1
A textile fibre must be strong enough to allow machinery to work and process it.
Tenacity is the term normally applied to the strength of individual fibres. It is measured in grams per denier or grams per tex or centi-Newtons per tex (cN/tex).
A strong fibre will normally produce a strong durable fabric, although this is not always the case.
Wool is a relatively weak fibre with low tenacity but due to other important properties such as elasticity and resilience, it can be used to make durable fabrics.
The tenacity of a wet fibre frequently differs from that of the same fibre when dry.
Some fibres, such as rayon, are weaker when wet and require careful laundering.
Cotton is stronger when wet and can be laundered with ease.

Question 5

3. Flexibility

Answer 5

Flexibility or pliability is the ability to bend without breaking. Textile fibres must not be too stiff or brittle, but must be pliable in order to form yarns and fabrics that can be creased, and can move and give with body with movement. Flexibility plays a role in fabric comfort. Flexibility depends on the chemical composition of the fibres. It is an important property that is related to abrasion resistance.

Question 6

4. Spinning quality/cohesiveness

Answer 6

Textile fibre must have the ability to stick together during yarn or non-woven manufacture. There are many fibres (human hair is one) that possess the first three primary properties but have no cohesiveness and therefore cannot be used as textile fibres. Fibre surface contours and crimp influence this cohesiveness.

Question 7

5. Uniformity

Answer 7

The fibres must be similar in length and width, in spinning quality and in flexibility.
Manufactured fibres can be controlled during production to maintain a relatively high degree of uniformity.
Natural fibres are not very uniform, since it is difficult to control all aspects of nature.
It is often necessary to blend fibres from many different batches to produce quality yarns and fabrics. Uniformity depends mainly on fibre length, diameter, cross-sectional shape and surface contours.