Determination of the heat of pyrolysis of HDPE via isothermal differential scanning calorimetry

Abstract

Due to the complexity of solid state reactions such as cracking of polymers, it is very difficult to find the required heat of the involved reactions. In this study, using a differential scanning calorimetry (DSC) instrument, a new method is proposed to determine the heat of decomposition of polymers at constant temperatures. The integration of an isothermal DSC curve with respect to time gives the overall consumed heat by the process, which consists of two components: net heat of reaction and heat loss. Finding an effective solution to measure heat loss from DSC instrument is an important part of this new approach. The heat loss is determined as function of sample mass and operating temperature. The heat loss is employed to correct the DSC results and produce the net heat of decomposition reactions. This approach is new since, firstly, it uses high-certainty isothermal DSC measurements, and secondly, the heat loss values are calculated in the decomposition range. The procedure is employed to determine the required heat for pyrolysis of high-density polyethylene at constant temperatures of 400, 410, 420 and 430 °C, and the average value was calculated to be 1375 ± 233 kJ kg−1.