An investigation of the relationship between the performance of polybenzoxazine and backbone structure of hyperbranched epoxy modifiers

Abstract

AbstractNovel hyperbranched polyether epoxies (HBPEEs) with various backbone structures were synthesized using a one‐pot A2 + B3 approach. These highly effective HBPEEs were incorporated into polybenzoxazine (PBOZ) network at various concentrations without cure‐induced phase separation. Effects of backbone structure and loading amount on the curing behavior and mechanical and thermal properties of PBOZ/HBPEE hybrid were investigated. The general trend shows that the impact strength, flexural strength and storage modulus all first increase and then decrease with filler content. For the backbone structure study, HBPEE‐3, which has the highest proportion of benzene rings, can simultaneously improve impact strength, flexural strength and storage modulus. In contrast, HBPEE‐1 and HBPEE‐2, which have fewer benzene rings and smaller intramolecular cavities, perform worse in terms of mechanical and thermal properties. Both backbone structure and loading of HBPEEs play important roles in determining the crosslink density and structures of non‐phase‐separated network. In addition, the simultaneous improvement can be explained by enhanced crosslinking density, structure of modifier, reduced hydrogen bond network and higher fractional free volume according to dynamic mechanical and thermomechanical analyses. © 2017 Society of Chemical Industry