Experimental and theoretical foundations are established for the limiting temperatures of thermal decomposition of thermoplastic polymers. The correlation between the limiting temperatures and the intermolecular interactions of the polymers investigated is reported.Experimental study of the kinetics of thermal decomposition. It was found earlier by TG and DTA methods that when the heating rate is increased up to some degrees per second, the thermoanalytical curves of polymers, shifted into the high-temperature region, assume extreme positions [1]. The limiting temperatures T/above which the initial materials no longer exist independently of the heating rate were determined. In this paper it will be demonstrated that above finding is valid for even higher heating rates too exceeding 103 deg/s. ExperimentalTo raise the heating rate, contact heaters made of high thermal conductivity metal were applied. The experiments were carried out in the following manner. The metal plate was heated to a constant temperature controlled by a steady-state potentiometer with an accuracy of + 6 ~ The substance to be studied was applied onto the surface of the plate as a thin layer of its melt. At film thicknesses of around 5 Ixm, the sample is clearly observable in reflected light. The heating time tn for a melt film of this thickness to attain the temperature T2 of the plate did not exceed 0.01 s, corresponding at T2 = 500 ~ (793 K) to an average heating rate of b = T/tn = 5.104 deg/s.

A new technique is presented for study of the thermal beha,viour of materials. Experimental and theoretical bases are established for the limiting temperatures of thermal decomposition of different polymers.