POLYPROPYLENE STABILIZATION - DURING GAMMA-IRRADIATION AND DURING POST-GAMMA STORAGE

The effects of additives on the stability of gamma-irradiated polyprop yrene film have been examined, both during irradiation and after prolo nged post-irradiation reaction up to the embrittlement point. Additive s were drawn from the tetramethylpiperidine family and compared with a conventional blocked phenol. Oxidation products from the polymer were determined by FTIR spectroscopy coupled with chemical derivatization. Polymer physical degradation was measured by an instrumented bend tes t. Although the stabilizers had very little effect on the radical prod ucts or oxidation products measured immediately after gamma-irradiatio n, very different oxidation product levels and distributions were foun d at the onset of brittle failure. Brittle failure occurred at a very low level of total oxidation products for the well-stabilized samples as compared to the unstabilized samples. Nevertheless ketonic product levels were very similar in all cases and the levels of carboxylic aci d and groups appreciably higher for the stabilized samples.