MASS-SPECTROSCOPY ANALYSIS OF VOLATILE PHOTOPRODUCTS IN PHOTOOXIDATION OF POLYPROPYLENE

Depending on their structure, photooxidising polymers can produce sign ificant concentrations of low molecular weight products formed by mult iple fragmentations of the main or branched chains. These photoproduct s can migrate out of the polymer matrix and consequently are not taken into account by analysis only of the solid sample. In some cases this may complicate the elucidation of the photooxidation mechanisms of th e corresponding polymers. This is why an analysis of the volatile prod ucts is sometimes required. We describe experiments based on the analy sis by mass spectroscopy of the gas phase obtained by photooxidation o f polypropylene. Because the photooxidation of this polymer is fairly well characterized, it was a good candidate to calibrate the apparatus and the analytical mode. One of the main advantages of using mass spe ctroscopy to analyse the gas phase is that this method requires virtua lly no separation of the different constituents before analysis. Howev er, we show that by using the different volatilities of the products f ormed in the polymer and in the gas phase, separation of the constitue nts can be obtained, which facilitates further analysis by mass spectr oscopy.