Secondary Heater for Yarn Set and Stretch Control
topic
Secondary heaters on false twist texturing machines treat the untwisted crimped yarn after the friction unit at 160 to 210 degrees Celsius for polyester over a short heater zone of 0.3 to 0.5 metres with controlled overfeed that allows the yarn to relax and contract during annealing, progressively reducing yarn stretch and elastic recovery from the high-stretch set-textured condition to the partially set or fully set condition required for weaving or warp knitting applications.
Role
Controls the yarn stretch and elastic recovery of false twist textured yarn through the degree of crimp annealing achieved in the secondary heater that determines whether the product is high-stretch for hosiery and stretch woven, semi-set for circular knitting, or fully set for non-stretch woven applications, with secondary heater temperature and yarn overfeed being the two variables governing this commercially critical product differentiation.
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