Effect of stoichiometry on chemical structure, dielectric and mechanical properties of epoxy resin under gamma irradiation

The chemical and physical properties of diglycidyl ethers of bisphenol-A (DGEBA)/2,2'-(ethylenedioxy) bis (ethylamine) (EDBA) epoxy resins with different stoichiometric ratios under gamma irradiation have been investigated. Fourier transform infrared (FTIR) spectroscopy results indicated that a mass of amines and oxidized carbonyl-containing products were generated during the irradiation process. Most products for amine-rich DGEBA/EDBA systems were amides. Dynamic mechanical analysis (DMA) and differential scanning calorim-etry (DSC) results demonstrated that chain scission predominated during irradiation for the amine-rich system, while chain cross-linking predominated for the epoxy-rich system. The dielectric relaxation behaviours indicated that the alpha relaxation behaviours broadened considerably with an increasing irradiation dose, demonstrating an increasing spatial heterogeneity of the crosslinked networks. The compressive yield strengths showed a monotonous linear increase with irradiation dose. However, due to the different cross-linking networks, the yield strains showed converse trends for amine-rich and epoxy-rich systems under gamma irradiation.