Function of Twist in yarn structure | Why twist is important for yarn
A question may arise why twist is given to yarn or what is the
function of twist. Actually twist plays a vital role in yarn manufacturing which
is given below -
1. The main function of twist is
to give a round shape to the yarns, increase the strength of yarn. As in sliver
no twist is given, therefore it is easy to open the fibre, but it is difficult
in case of roving or yarn.
2. Without twist a strand of
fibres 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.
3. The main function of twist is
to give coherence to the yarn. In order to develop strength in a twisted strand
of discontinuous fibres and so resist breakage, the individual fibres must grip
each other when the strand is stressed. This cohesion arises mainly from the
twist, which presses the fibres together as the stretching force is applied and
so developing friction between adjacent fibres.
4. If the twist is low, the
fibres can be made to slide past one another, but if it is large they cannot.
The twist can be termed as twist angle that means when twist angle is high,
then yarn strength is high. An experiment shows that, when twist is increased
then yarn strength increases within a certain limit and at a point called
critical point the maximum strength of yarn is obtained. But after critical point
at the end increasing the tension goes to the rupture the strand by breaking
the component fibres.
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