An enclosed Curie point pyrolysis-GC technique for studying the oxidative or thermal degradation of polymers and volatile oligomeric oils

Abstract

The technique of pyrolysis-GC has been extended to the study of oxidative degradation by a method that can also deal with volatile oil samples and oligomers. This has been done by pre-degrading the sample in a sealed capillary tube containing either air or inert gas, and then breaking open this tube within the carrier gas flow at the injection port of a GC apparatus. This approach is possible because the sample is deposited on a Curie-point filament wire within the sealed tube, and this wire can be rapidly heated in the usual way by an external RF field. The new technique can therefore be described as enclosed Curie-point pyrolysis (ECP). Although there is a need for improving the reproducibility of the absolute product yields obtained by ECP, the relative yields of products display very good reproducibility. Examples of the use of the approach to study the oxidation of polyisobutylene oils are provided. The results show distinct oxidation products which are not present in the thermolysis pyrograms. A comparison of results from conventional resistive filament pyrolysis with those from the ECP method provides a procedure for distinguishing gas-phase versus melt-phase secondary reactions of the pyrolysis and oxidation products.