Synthesis of degradable hyperbranched epoxy resins with high tensile, elongation, modulus and low-temperature resistance

Abstract Hyperbranched epoxy resins (HERs) have attracted much interest due to improving homogeneously the ductility and strength of popular diglycidyl ether of bisphenol-A (DGEBA), but the preparation of HERs/DGEBA composites with low-temperature resistance and rapid degradation is still a challenge in the sustainable development of thermoset field. Here we represent self-curable hyperbranched epoxy resins (DSEHP-n, n = 3, 5, 7, 11) to modify DGEBA. DSEHP-n not only increases simultaneously the tensile strength, flexural strength, impact strength, modulus, and elongation by 64.8%, 38.1%, 93.7%, 70.4%, and 50%, respectively, and but also improve remarkably the low-temperature resistance and degradation degree. The improvement of mechanical properties is caused by the combined effect of crosslinking density, free volume, intermolecular cavity, hyperbranched topological structure, and good compatibility, the account of an in-situ reinforcing and toughening mechanism which substantiated by dynamic light scattering (DLS), SEM, DMA, and free volume analysis. The detailed analysis of degradation products from GC-MS spectra showed that the degradation of the composites was attributed to the cleavage of the C–N and ester bonds. This paper will bring a novel method to prepare highly-efficient degradable thermosets and composites.