The effect of the composition on the properties of?-irradiated ethylenevinyl alcohol copolymers

Abstract

Two ethylene-vinyl alcohol copolymers (Eval E and Eval F with about 45% and 25% of ethylene respectively) have been irradiated in air in the dose range 0-200 Mrad. The irradiated samples show both crosslinking and degradation; the former effect is more relevant in the copolymer with a larger content of polyethylene. Calorimetric results show that both the crystalline and the amorphous phases are involved in the reactions initiated by the irradiation.

The effect of the composition on the properties of ?-irradiated ethylenvinyl alcohol copolymers

“…Stress-strain and dynamic-mechanical tests on both irradiated and non-irradiated samples confirm the structural modifications already discussed [1], namely that both crosslinking and chain scission follow irradiation, and that a significant decrease in the degree of crystallinity occurs with increasing irradiation dose.…”

“…2 and 4) : a decrease in crystattini~y which causes a slight decrease in the complex modulus E" with irradiation dose. This is in spite of the crosslinking already mentioned [1], whose effect is, however, well evident at temperature above the glass transition. As for the dissipation factor data (figs.…”

“…For Eval E moduli quite rapidly decrease by about 10% with an irradiation dose in the range of 20 Mrad, and then show a levelling off. The behaviour of Eval F is similar, although the change is not as rapid as with Eval E. According to the structural data already reported in [1], this behaviour may be explained by the decrease in crystallinity following the irradiation, which varies in proportion to the dose. The levellingof~ is thought to be due to the primary effect that the radiation has on such copolymers: namely the crosslinking.…”

“…The height of the maximum seems mostly uneffected by the irradiation, perhaps because it depends also on the degree of crystallinity [5], which certainly decreases with dose. Finally, a good quantitative comparison may be seen in table 2 between the glass transition data revealed by the maximum in the E"-T plot and previous calorimetric results [1].…”

“…Following previous work [1], the effect of yirradiation on the mechanical properties of two ethylene-vinyl alcohol copolymers differing in ethylene content (25% and 45% respectively) has been considered. The purpose of this was to evaluate the copolymers better in view of some applications and further to evidence changes in the structure.…”