Thermal and viscoelastic properties of epoxy blends modified with nano modifier for RTM applications

Rheological, thermomechanical and fracture properties of a diglycidyl ether of bisphenol A epoxy resins modified with either trisilanol isoctyl POSS or trisilanol isobutyl POSS (polyhedral oligomeric silsesquioxane) and a third generation hyperbranched polyester have been studied. All the formulations have been cured with a two step process : first with a pre-cure for 5 h at 120 °C or 155 °C followed by a post-cure at 180 °C for 5 h. The polyhedral oligomeric silsesquioxanes were added in small amounts (0.25 and 0.5 Wt.%). It was found that POSS molecules greatly increased the glass transition temperature of the post-cured samples without any increases in viscosity thus favoring the processing of the blends with RTM (resin transfer molding) equipments. Blends of epoxy resin with POSS and 15Wt.% of hyperbranched polymer were also studied. The addition of the hyperbranched polymer was detrimental to the improvement of the thermal properties found with the epoxies modified only with POSS. No significant change in the fracture resistance was found with the addition of the POSS molecules whether the hyperbranched polymer increased the toughness of the resin.