Epoxy/poly(4-vinylphenol) blends crosslinked by imidazole initiation

Poly(4-vinylphenol) (PVPh) was used as thermoplastic modifier of epoxy resins. Binary epoxy/PVPh mixtures with high thermoplastic content rise high glass transition temperatures (T _g) after heating, due to the epoxy-phenol reaction. Blends with low PVPh percentages reach high T _g if 2-methylimidazole is added, which catalyses epoxy homopolymerisation and epoxy-phenol reaction. The cured blends do not present phase separation although the network structure depends on the epoxy/phenol ratio. At low PVPh percentage the main crosslinking reaction is epoxy-epoxy but, when the thermoplastic content increases, the epoxy-phenol reaction prevails, causing an important T _g increase and becoming less brittle.