Abstract
Isocyanate-terminated urethanes with polyoxypropylene glycols (PPGs) 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 chain extended by polyurethanes (PUs) and dicyandiamide as a hardener. The relationships between the properties of cured epoxy resins and molecular weight (MW) of PPGs in PUs were investigated. The MW of PPGs remarkably affected the adhesive properties and morphology. In case of PPG-Diol, the compatibilities of PPGs/epoxy resin decreased with the increasing MW of PPGs. The dynamic viscoelastic properties showed that the higher MW-PPGs were easy to form the phase separation structures. The adhesive strength about Diol-2000 type was the highest in all PPGs. The hydroxy group equivalent of PPGs was one of the most important factor about the compatibility between epoxy resin and PUs because of the similar properties of adhesive strength and morphology about Triol-3000 and Diol-2000 type.
