DEGRADATION MECHANISMS OF POLY(METHYL ACRYLATE) .1. AN ASSESSMENT OF THE PARTICIPATION OF RANDOM CHAIN SCISSIONS

Thin films of poly(methyl acrylate) (PMA) have been degraded thermally using a thermocouple-feedback-controlled filament, and the products a nalysed by gas chromatography (GC). Total pyrolysis experiments (in wh ich all the sample decomposed to volatiles) were carried out at temper atures not exceeding 700 degrees C for 30 s on (a) a 'thick' sample of mass 10 mu g and (b) a 'thin' sample of mass 1 mu g, deposited in eac h case on a small, fixed area of the filament. The number- and weight- distribution of the oligomeric products, calculated from the GC result s, have been compared with those predicted statistically on the basis of random scission. The results show that random scissions do not play a significant part in the mechanism for the thermal degradation of PM A. The observed distribution of oligomeric products indicates that it is more likely that depropagation, accompanied by intramolecular trans fer, is the predominant degradation pathway. (C) 1997 Elsevier Science Limited.