Synthesis of epoxy-ended hyperbranched polyesters with reinforcing and toughening function for diglycidyl ether of bisphenol-A

Hyperbranched epoxy resins are excellent materials for toughening and reinforcing diglycidyl ether of bisphenol-A (DGEBA), but the glass transition temperature usually decrease sharply. Here we report synthesis of novel epoxy-ended hyperbranched polyesters (HEHP-n, n = 1, 2, 3, and 4) with different molecular weights. Chemical structure of the HEHP-n and intermediates were characterized by FT-IR and H-1 NMR. The HEHP-n has shown remarkable effect for toughening and reinforcing DGEBA. The mechanical strength of the HEHP-n/DGEBA composites first increased and then decreased as the molecular weight and content of HEHP-n increased. When the composites contain 12 wt% HEHP-3, the impact, flexural and tensile strengths of the cured HEHP-n/DGEBA composites reached 48.0 kJ/m(2), 41.2 MPa, and 74.8 MPa, respectively, which are 223.6%, 73.0%, and 46.1% higher than those of the cured DGEBA. The glass transition temperature of the cured HEHP-n/DGEBA also increased in comparison with that of the epoxy-ended hyperbranched polyesters/DGEBA composites reported previously. POLYM. COMPOS., 39:E2046-E2055, 2018. (c) 2017 Society of Plastics Engineers