Study of Thermal Degradation of Fractionated Polystyrenes by Pyrolysis Gas Chromatography

Abstract

Direct examination was made of the thermal degradation of fractionated polystyrenes (PS) utilizing pyrolysis gas chromatography (PGC). Pyrolysis was carried out in a nitrogen gas stream in the temperature range of 515 to 650°C with eight fractions of PS of narrow-range molecular weight (MW) ranging from 900 to 1,800,000. Yield of each component of the degradation products was examined as a function of MW and the pyrolysis temperature. The monomer yield was found to increase with increase of MW of PS and to decrease with the elevation of the pyrolysis temperature. It was confirmed that PS first degrades rapidly to a certain level (L) regardless of its MW, and that the subsequent unzipping takes place, provided that the initial MW is above the L. The value of the L changes as a function of the pyrolysis temperature; L₁ = 25,000 at 550°C, L₂ = 17,000 at 580°C and L₃ = 12,000 at 650°C.