Hyperbranched Polyester-modified Phenolic Epoxy Preliminary Study

Epoxy resin is one of the most widely used thermosetting materials with attractive properties, such as high strength and stiffness, excellent adhesive property, anti-corrosion, insulating as well as thermal properties. One of the drawbacks of cured epoxy materials is their inherent brittleness due to the high cross-linked network structure. Hyperbranched polymer(HBP) is a new modifier for epoxy resins with excellent processing properties. HBP has unique properties, such as lcw viscosity and high thermal stability, which extend good potential for epoxy modifying and toughening. Contrasting to linear polymer with similar level of molecular weight, HBP shows easier solubility and higher reactivity. The abundant end groups can also be modified to adjust necessary properties.This paper is focusing on novolac epoxy modified with synthesized hyperbranched polyester(HBPE) and studying the modifying effect for material performance:Hyperbranched polyester is synthesized through A2+B3 route from 2,2-Bis [4-(2-hydroxyethoxy)phenyl]propane(D22) and 1,3,5-Benzenetricarboxylic acid. The hyperbranched polyester is analyzed with FTIR,1HNMR,13CNMR,GPC for material characterization.The composites of novolac epoxy/HBPE are prepared, varied with HBPE by different weight percent. The mechanical properties, processing, thermal stability and morphology of composites are studied by using impact, tensile, DMA, rheometer and SEM test. The detailed results are as following from a series of experiments:HBPE has no obvious impact on processing for epoxy resin. HBPE can improve the toughness of epoxy resin without obvious impact on other mechanical and thermal properties. HBPE can decrease the epoxy shrinkage. The novolac epoxy of around 10%HBPE modified has the best balanced properties among the designed experiments.The composites of novolac epoxy/HBPE/silica powder are prepared, fixed HBPE by 5% and 10% and varied with silica powder by different weight percent. The processing and mechanical properties of composites are studied by using impact, tensile and rheometer test. The detailed results are as following from a series of experiments:HBPE can reduce the impact on viscosity of HBPE/silica powder modifying composite and contribute for processing stable. HBPE/silica powder can decrease the epoxy shrinkage. HBPE/silica powder can improve modulus of the epoxy resin. The novolac epoxy of around 10%HBPE/20%silica powder modified has the best balanced properties among the designed experiments.