Tempering of acrylic twists in oxidative thermal stabilization

Oxidative thermal stabilization of acrylic twists has a relatively high rate at a temperature close to the temperature of autocatalytic heating (250–260°C). To conduct the process at this temperature, it is necessary to temper the twists, not allowing the temperature in the core of the twist to increase by more than 5–6°C. In this case, conductive tempering is the most appropriate method. It was shown that in conductive tempering of acrylic tape 2 mm thick between two metal plates with the maximum possible exothermic effect of 60 cal/(g·sec), the change in the temperature in the core of the twist does not exceed 2°C, while in convective heat transfer, heating of the twist can attain 10°C for a tempering air flow rate of 5 m/sec. It was hypothesized that the more intensive heat transfer in conductive tempering in comparison to convective tempering is due to the high thermal conductivity of the contacting material and the absence of a boundary layer of air through which heat transfer takes place slowly with the convective method due to the low thermal conductivity of air. It was experimentally shown that in conductive tempering of twists, the duration of oxidative thermal stabilization can be reduced to 30 min.