Abstract
Isocyanate-terminated urethanes with three kind of macroglycols (polyether type, polycarbonate type and polybutadiene type) as a softsegment were reacted with the mixture of two bisphenol-A type epoxy resins which had secondary hydroxy groups. One component epoxy adhesives were prepared with the epoxy resins chainextended by polyurethanes (PUs) and dicyandiamide as a hardener. The relationships between the properties of cured epoxy resins and chemical structures of softsegments in PUs were investigated. As for the adhesive strength polycarbonate (PCG-PUs) type increased with the reacting amount of PUs, polyeter (PTMG-PUs) type and polybutadiene (HTPB-PUs) occurred higher adhesive strength at the low reacting amount. It was considered that the compatibility of epoxy resin and PUs were affected by softsegments in PUs. The results of dynamic viscoelasticity and scanning electron microscopy showed that PCG-PUs type didn't form phase separation structure because of good compatibility with epoxy resin, PTMG-PUs and HTPB-PUs type formed the phase separation structure. Especially PTMG-PUs type had the excellent adhesive strength to be suitable for structural adhesive for steel.
