ON THE CHANGE IN THE THERMAL-BEHAVIOR OF THE COMPOUND EVA OWING TO ACCELERATED THERMAL AND RADIATION-INDUCED AGING

A derivatographic investigation has allowed us to demonstrate the changes undergone by the compound EVA as a consequence of thermal and radiation-induced ageing. For samples thermally aged at 130, 145 and 180° C, as well as for those aged through γ-irradiation with a dose rate of 0.1 MRad h-1, two kinds of thermo-oxidative degradation have been found, which occur on heating the samples in air: an initial exothermic effect accompanied by a slight weight increase and exothermic effects accompanied by loss of volatile compounds. Up to 340 ° C, the thermally aged samples exhibit two successive exothermic effects accompanied by loss of weight, while the irradiated ones exhibit only one such exothermic effect. The thermally aged samples heated in air up to 340 ° C exhibit a weight loss of 16-21% while the weight loss corresponding to the sample aged through irradiation is 28-30%. The results obtained by thermal analysis have been correlated with the results concerning the relative elongation at break following accelerated thermal and irradiation-induced ageing. © 1990.