Modification of Epoxy Resins with Polyether-g-polysiloxanes

To improve the toughness of epoxy resin, and clarify the complex interrelationship between the miscibility, morphology, toughness and composition of epoxy resin/graft copolymer blends, amphiphilic polysiloxane graft copolymers (F6-PMSs) with different contents of polyether were synthesized via hydrosilylation between epoxy-immiscible poly(methylhydrosiloxane) and epoxy-miscible allyl polyoxyethylene polyoxypropylene ether (F6) to modify diglycidyl ether of bisphenol A (DGEBA). The miscibility of amphiphilic graft copolymers with epoxy resin was investigated by observing the transparency of the modified epoxies before and after curing and by detecting the glass transition temperature (Tg) of the cured epoxies using differential scanning calorimetry. The morphologies of the cured epoxies were studied by scanning electron microscopy, and the toughness in terms of tensile and impact strength were examined by tensile and impact testing. Results indicated to higher miscibility of polysiloxane with DGEBA by grafting with polyether. Relative to the neat epoxy network, the polysiloxane modified epoxies exhibited lower Tgs and with the increased polyether in graft copolymer, there was a decreasing trend noticed in Tg . The nanostructures were obtained for the modified epoxies with different F6 to PMS ratios (5 wt% of DGEBA). The formation of the nanostructures in the thermosetting composites was judged by following the self-assembly and reaction-induced mechanisms, mainly dependent on the miscibility of graft copolymer with epoxy resin. Moreover, toughness of the epoxy networks was greatly improved by F6-PMS of 100/100 weight ratio at relatively low addition levels.