The effect of Gamma and EB irradiation on the mechanical properties of thermosetting polymers and their composites

The degradation mechanism in molecular order by electron beam (EB) irradiation for three types of thermosetting polymers (bisphenol type vinylester, Novolak-type vinylester and tetra functional epoxy resin) is confirmed by dynamic mechanical thermal analysis (DMTA) and the swelling test in this study. The level of degradation in molecular order is quite high. The same result was observed in Novolak-type vinylester but not in tetrafunctional epoxy resin. The results of the swelling test showed that the cross-linking networks were destroyed by γ- or electron beam irradiation remarkably for both the vinylester resins. For the tetrafunctional epoxy resin, γ- or electron irradiation does not give any effect even in molecular order in high radiation intensity such as 20 MGy. However, the mechanical properties such as bending strength, modulus and fracture toughness of all composites (both vinylester resin and tetrafunctional epoxy resin composites) reinforced by a chopped-strand glass mat or flake-like mica change a little after 20 MGy EB irradiation. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd.