The effect of amino-terminated hyperbranched polymers on the impact resistance of epoxy resins

A novel amino-terminated hyperbranched polymer (ATHBP) was synthesized through the end-capping reaction between hyperbranched polymer with hydroxyl group (HBPH) and diethylenetriamine. The chemical structure of ATHBP was characterized by attenuated total internal reflectance infrared spectroscopy (ATR-IR) and H-1 nuclear magnetic resonance spectroscopy (H-1 NMR). The effect of ATHBP content (0-30 wt%) on the impact resistance and glass transition temperature (Tg) of diglycidyl ether of bisphenol-A epoxy resin was studied. The toughness mechanism was discussed by observing the fracture surface morphologies of epoxy thermosets using field emission scanning electron microscopy (FESEM). The results showed that the degree of branching of ATHBP was 0.56. And the introduction of ATHBP could favorably improve the impact strength but not sacrifice the Tg of epoxy resin. For example, the impact strength of 25 wt% formulation was 60.7 % higher than that of the neat epoxy thermoset. FESEM analysis indicated that the toughening mechanism may be attributed to plastic deformation mechanism.