Mechanism of the thermal decomposition of polystyrene peroxide

Abstract

The thermal degradation of polystyrene peroxide was carried out using differential scanning calorimetry. The activation energy (E) was found to be 136 kJ mole -1 at all extents of decomposition. The E value was found to correspond to --O-O--dissociation. The order of reaction was found to decrease from 2 to 1 as the decomposition progresses, and the mechanism of the changeover was explained.The nuclear magnetic resonance spectra (NMR), differential thermal analysis (DTA) and differential scanning calorimetric (DSC) analysis of pure polystyrene (PSP) have recently been reported [1 ]. Further, the kinetics of PSP decomposition have been studied by isothermal thermogravimetry (TG) [2]. The activation energy (E) was found to be 136 kJ mole -1 and it was suggested that the rate-controlling step is -O-Obond dissociation [2]. The order of reaction (n) and the detailed mechanism for pure PSP decomposition have not been reported so far.It has been shown that DSC can be used to study the kinetics of the process and that E can be derived without recourse to kinetic assumptions [3]. PSP decomposition was carried out by using the DSC technique (Perkin-Elmer DSC-1B), and the kinetic parameters such as E and n were evaluated to understand the mechanism.The details of the operation of the instrument and the derivation of the fraction decomposed (ct) vs. time (t) or vs. temperature (T) plots from the thermal curves are described elsewhere [3]. Thermal curves obtained in the scanning modes were used for kinetic analysis. The shapes of the DSC curves of PSP can be seen elsewhere [1 ].E was calculated by using the following equation :where S is the DSC signal in millicalories per second for full-scale deflection, AH is the total heat of PSP decomposition, A is the frequency factor and R is the S 1 gas constant. From Eq. (1), E was obtained by plotting In ~ vs. -~. In doing so, and n were kept constant, a was fixed at a definite value for the curves at different heating rates, and the constancy of n was checked from the reduced-time plots

Distribution Changes during Thermal Degradation of Poly(styrene peroxide) by Pairing Tree-Based Kinetic Monte Carlo and Artificial Intelligence Tools

“…The pyrolysis of PSP has been studied experimentally by Kishore and co-workers as well. − ,− These authors used differential scanning calorimetry (DSC) to report an exothermic decomposition around 100 °C, which is a characteristic of peroxide bond breakage . Kishore and Ravindran calculated the heat of degradation as ca.…”