Analysis of Solubility Data to estimate Small Amounts of Chain Fracture during the Cross-linking of Rubber

Abstract

IN a communication1 on methods of estimating chain fracture during the cross-linking of rubber by high-energy radiation, we mentioned that a quantitative analysis of solubility data was not attempted because results did not conform with a theoretical relationship derived by Charlesby and Pinner2. This relates the sol fraction (S) after dose R with the fracture and cross-link densities (p and q, respectively) and includes as a parameter the number average degree of polymerization before irradiation (u). This relationship (1) applies only for a polymer with a random molecular weight distribution and for the case where fracture and cross-linking are random and proportional to the dose. Hayden3 has recently reported results which apparently do conform with this relationship. These are now contrasted with our previous results in order to emphasize some limitations concerning the general utility of this method for estimating small ratios of fractures to cross-links.