Thermal Decomposition Processes in Polycarbonates

The thermal decomposition mechanisms of some polycarbonates have been investigated by direct pyrolysis mass spectrometry. The results indicate that aliphatic polycarbonates decompose by intramolecular exchange processes which produce cyclic compounds as primary pyrolysis products. Aliphatic-aromatic polycarbonates yield cyclic compunds conteining various ratios of bisphenol A (BPA) and aliphatic carbonates. Poly(Ethylene-co-BPA carbonate) decomposes to produce ethylene carbonate and BPA polycarbonate. The latter further decomposes at higher temeperature ti yield cyclic oligomers. Alt-copoly(resorcinol-co.BPA carbonate) undergoes ester-exchange rearangement to produce cyclic resorcinol carbonate oligomers and BPA polycarbonate.