A novel liquid hyperbranched polyether epoxy （HBPEE） based on commercially available hydroquinone （HQ） and 1,1,1-trihydroxymethylpropane triglycidyl ether （TMPGE） was synthesized through an A2 ＋ B3 one-step proton transfer polymerization. In order to improve the toughness, the synthesized HBPEE was mixed with diglycidyl ether of bisphenol A （DGEBA） in different ratios to form hybrids and cured with triethylenetetramine （TETA）. Thermal and mechanical properties of the cured hybrids were evaluated. Results show that addition of HBPEE can improve the toughness of cured hybrids remarkably at 〈 20 wt% loading, without compromising the tensile strength. However, the glass transition temperature （Tg） of the cured hybrids decreases with increasing HBPEE content. Fracture surface images from scanning electron microscope show oriented fibrils in hybrids containing HBPEE. The formation and orientation of the fibrils can absorb energy under impact and lead to an improvement of toughness. Furthermore, based on the morphology of fractured surfaces and the single Tg in each hybrid, no sign of phase separation was found in the cured hybrid systems. As a result, the toughening mechanism could be explained by in situ homogeneous toughening mechanism rather than phase separation mechanism.
Epoxy-terminated hyperbranched polymers （EHBPs） were prepared by proton transfer polymerization and characterized by FT-IR, 1H-NMR and GPC. The solution and thermal properties of the uncured samples and mechanical properties of cured samples were examined. The thermo-stable products had good solubility in polar solvents, low solution viscosity and Tgs ranging from 15℃ to 33℃ depending on their molecular weights. The mechanical properties of cured films were studied and compared with those of a bisphenol-A type epoxy resin. The films of EHBPs had good impact resistance and high gloss values without sacrificing hardness and adhesion.
