Studies on thermal and morphological characteristics of siloxane containing epoxy resins cured by microwave radiation

Microwave radiation was performed on a diglycidyl ether of a bisphenol-A type epoxy monomer with an aliphatic polyamino-curing agent. The ratio of epoxy monomer to curing agent was taken as 2. Two different molecular weights of silicone acrylates were used in various ratios for the modification of the system. The mechanical characterisation and hardness measurements of these samples were performed. As the siloxane content in the epoxy resin system was increased, Young's modulus and hardness decreased. Further, the strength at F_max, toughness and percentage elongation showed a maximum of about 10% for one kind of PDMS containing epoxy system. Thermal characterisations of the samples were determined with a thermogravimetric analyzer. The decomposition of the samples was a two-stage process with maximum weight loss rates in between 320 to 400°C or 330 to 430°C°C, depending on the molecular weights of PDMS modifier. The SEM photographs of the cold-fractured samples were taken. As the siloxane content in the epoxy resins was increased, the fractured surfaces became rougher and showed more irregular stripes in the matrix.