Hyperbranched polymers as modifiers of epoxy adhesives

A novel hyperbranched poly(amide-ester)s (HBP) has been synthesized through the AB2 approach in one-step polycondensation without solvents. The synthesized HBP has been characterized and used as filler for epoxy resin with the aim obtain materials which exhibit improved toughness. Composites containing 6% and 12% wt/wt of HBP in diglycidylether of bisphenol A (DGEBA) were produced and characterized. Results obtained from DMA tests showed that HBP has good compatibility with the epoxy resin. Impact tests proved that composites containing 12% HBP showed an improvement of about 25% on impact strength with respect to neat DGEBA. Moreover, adhesive properties were evaluated in terms of the lap-shear strength value of composite joints bonded using the investigated blend. Results showed an improvement of shear strength value of DGEBA added with 12% HBP with respect to neat DGEBA. The water uptake behavior was also evaluated.