Abstract
The tension of running yarn during twist setting with a heating plate was studied in terms of the original yarn's physical properties.
The results obtained are as follows:
(1) The heat shrinkage of the original yarn caused by heating in the static state is influenced by the thermal hysteresis during spinning process, and this phenomenon depends on the characteristics of the original yarn. However, in the case of the hard twist yarn, the shrinkage did not occur, because the effects of twisting torque and elasticity caused by its spiral shape are large.
(2) When the circumferential velocity of a feed roller equals a delivery roller's velocity, the tension during heat-setting can be estimated by the distance of the rollers, heater length and stress-strain behaviour of twist-setted yarn.
(3) When the yarn tension during re-heating is too large, the twisting torque does not appear, because molecular chains begin to flow. Accordingly in order to obtain the high-quality crepe fabric, it is necessary to determine the scouring condition considering the twist-set temperature and the thermal hysteresis of the original yarn.
