User:Md Hasan Emam

Twist & Twist Measuremen

Definition of Yarn twist:

	Twist is the measure of the spiral turns given to a yarn in order to hold the constituent fibers or threads together.

	According to textile institute “twist is the spiral disposable of the component of a thread which is usually the result of relative rotation of the two ends ”.

The function of twist in yarn structure:

Without twist a strand of fiber has very little strength and in the first instance a yarn must have sufficient tensile strength to withstand the stresses of preparation  and fabric manufacture.

-The main function of twist is to given coherence of the yarn.

Effect of twist in yarn strength:

The strength verses twist curve can be divided into two section-

1.	A low twist region in which the effect of cohesion INCREASES, giving rise to an increase in strength slow at first up to the point at which fibers may just begin to break and increasing rapidly as more and more fibers break.

2.	A high twist region in which further increase in cohesion no longer produces and increase in strength since the majority of the fibers break, while the increasing inclination of the fibers causes the strength to fall. The division between the two regions corresponds to the twist at which the maximum strength is realized. At this twist the greater proportion of the fibers break.

Twist direction:

The direction of twist is indicated by the use of the letter’S’ and ‘Z’ in accordance with the following conversion.

S-twist:

A single yarn has S twist if when it is held in the vertical position ,the fibres inclined to the axis of the yarn conform in direction of slop to the central position of the letter ’S’.

Z-twister:

The yarn has Z twist if the fibers inclined to the axis of the yarn conform in direction of slope the central portion of the letter 'Z’.

Method of twist measurement:

1.	The ordinary twist tester

2.	Take-up twist tester

3.	The Quadrant twist tester

4.	Twist measurement by microscope

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