Electron beam irradiation of epoxidized natural rubber

The effect of irradiation on ENR50 was studied with particular attention to irradiation-induced crosslinking. ENR50 was irradiated by using a 3.0 MeV electron beam machine with doses ranging from 20 to 200 kGy. The influence of several additives such as TMPTA, Irganox1010 and tribasic lead sulfate on irrradiation-induced crosslinking of ENR50 was investigated. The gel fraction, Ts, M100, Eb, hardness and Tg were used to follow the irradiation-induced crosslinking of the rubber. Results revealed that the increase in gel fraction upon irradiation of pure ENR50 could be associated with both irradiation-induced crosslinking as well as ring opening side chain reaction of oxirane group. The observation on the trend shown in the properties studied confirmed that TMPTA is efficient in enhancing the irradiation-induced crosslinking of ENR50. The addition of Irganox1010 and tribasic lead sulfate found to inhibit irradiation-induced crosslinking of ENR50 to considerable extent. This influence of stabilizing additives in particular, antioxidant, was observed to be more prominent at lower doses. The importance of TMPTA in preventing ring opening side chain reactions as well as the role of the stabilizing additives in introducing free chain ends are also discussed. However studies did not reveal the exact nature of irradiation-induced reactions involved in ENR. (C) 2000 Elsevier Science B.V. All rights reserved.