Effect of heating rate on oxidative degradation of polymeric materials

Abstract

The rate at which a final pyrolysis temperature is achieved may have significant effects on the types and amounts of compounds produced as result of the pyrolysis. This is particularly pronounced when very slow heating rates (1–5°C/min) are compared to very fast rates (20°C/ms). When the sample material is heated in the presence of oxygen, the effects may be even more significant. To study the evolution of compounds from the oxidative degradation of polymers, the samples were thermally processed in a pyrolysis chamber which was swept with a flow of air during heating. The air was vented and the pyrolysis products were retained on the surface of a sorbent trap. To protect the gas chromatographic column from damage caused by the introduction of oxygen, the trap was flushed with helium to remove residual air before transfer to the gas chromatograph. The trap was then pulse-heated to thermally desorb the pyrolysates into the carrier gas stream of the gas chromatograph. The resulting chromatograms show that the predominant materials produced by this thermal processing change, depending on the rate at which the sample was heated.