Thermal degradation of monodisperse polystyrene in bean oil

Thermal degradation of monodisperse polystyrene (PS) in bean oil was investigated in the temperature range of 305-350 degreesC. The degradation products were identified by means of gel permeation chromatography (GPC) and Fourier transform infrared spectrometry (FTIR). A significant feature for the investigated system was that PS in the presence of bean oil thermally degraded into larger fragments of the polymer chain instead of monomer or oligomers which are usually generated in the direct thermal degradation. The average molecular weights of degradation products of PS decreased and the polydispersity indexes (M-w/M-n) increased but did not exceed 2 as the reaction time increased. The kinetics of the degradation reaction was also examined based on the GPC measurements. The results revealed that the degradation of PS in bean oil was a first order reaction and the energy of activation for chain scission was 215 kJ mol(-1). The thermal degradation of PS in bean oil is believed to be a random chain scission process involving radical intermolecular transfer between bean oil and intermediate macroradicals of PS. (C) 2001 Elsevier Science Ltd. All rights reserved.