DTA of polyacrylonitrile fibers in air

The effect of experimental conditions on the results of DTA of polyacrylonitrile fiber in air and in helium over the temperature range from 200 to 400°C has been investigated. It is shown that such DTA factors as the heating rate, the sample weight, the crucible size and the location of the thermocouple are of primary importance when the thermal analysis of the PAN fiber is carried out in air. The character of the effect of these factors suggests that the thermal transformation of PAN and its oxidation are interrelated. However, when the access of air is limited and the heating rate is high, these processes are separated, which is shown by two maxima on the DTA curve.