This study is concerned with the behavior of stretch textured thermoplastic yam during its continuous movement through a second heater. Measurements are re ported on the influence of primary and secondary heater temperatures, as well as overfeed levels on yarn contraction, residual crimp, and filament shrinkage. Further evidence is presented of the pseudo twister effect, that is, the thermal motivation for second zone false twisting of the threadline without the aid of a mechanical twisting device. On the basis of auxiliary thermomechanical experiments, a semiquantitative mechanism is proposed to explain this behavior.
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