Structure change of elastomer by irradiation, (3)

The changes of C1 and C2 of Mooney-Rivlin plot of elastomer by irradiation was studied. The sample used is tetrafluoroethylene-propylene copolymer. Scission reaction of the polymer chain is predominant when the diffusion of oxygen is sufficient enough during irradiation. On the other hand, irradiation without oxygen in the polymer increases the cross-linking density. The result for three cases are as follows: (1) Values of C1 increase and that of C2 decrease with increasing dose when the cross-linking density of the elastomer increase by irradiation. (2) Both C1 and C2 decreases with increasing dose when the irradiation causes a decrease in cross-linking density of the polymer. (3) The third case, where the cross-linking density was maintained the constant by the alternative irradiation of γray (60 kGy) and electron beam (40 kGy). The operation (alternating irradiation) causes the same amount of scission and cross-linking in the polymer. C1 increases slightly with increasing the times of operation and C2 decreases with increasing the times of that. The result suggests that C2 decreases with decreasing the effective long network chain by irradiation. (author)