Protective effect of nitrous oxide on radiation‐induced degradation of polyisobutylene

Abstract Polyisobutylene was irradiated by γ‐rays from a Co60 source in vacuum and in nitrous oxide atmosphere. The irradiated specimens in N2O were damaged to a lesser extent than those in vacuum. Irradiated specimens were dissolved in CCl4 and their viscosity was measured at 30°C. A plot of reciprocal of viscosity‐average molecular weight against dose gives a straight line in each case for specimens irradiated in vacuum and in N2O. Moreover, the presence of nitrous oxide reduces the extent of main‐chain fracture to 63%. The degree of branching is nearly the same for all of the specimens, since Huggins' constant k' is constant (k' = 0.40) throughout our experiments. It can be concluded that the N2O has a protective effect for main‐chain fracture of polyisobutylene.