How the Polymer Structure Can Influence Cross-linking?
Polymer structure influences the cross-linking ability of polymer. Chain cross-linking and scission are the two reactions that occur during EB processing of polymers. Polymers typically undergo simultaneous scission and cross-linking, but in most-cases with one or the other clearly predominating. Polymers irradiated in absence of oxygen can be grouped into two categories, in terms of predominance of scission and cross-linking2. A very useful rule of thumb for predicting whether cross-linking or scission prevails, holds for a large number of polyolefins: Polymers with a high concentration of quaternary carbon atoms along the chain (poly-isobutylene), poly(methyl methacrylate), poly(alpha-methyl styrene)) mainly undergo scission; while other polymers such as poly(ethylene), poly(styrene) and natural rubber mainly undergo cross-linking. Presence of relatively bulky F in poly(tetrafluoroethylene), PTFE or –CH3 (methyl) group in poly(propylene), PP (as compared to H in PE) leads to chain-sc
