Epoxy-functionalized star-shaped polymers as novel tougheners for epoxy resin

A novel epoxy resin toughener based on star-shaped copolymer of butyl acrylate (BA) and glycidyl methacrylate (GMA) [poly (BA- co -GMA)] with low viscosity was developed. The star polymers were synthesized by initiators for continuous activator regeneration atom transfer radical polymerization (ICAR ATRP) using tri, tetra and hexa-functional initiators. The branching parameters of star poly (BA- co -GMA) were characterized by gel permeation chromatography with a laser light scattering-viscometry triple detection system. Copolymer composition and glass transition temperatures of the copolymers were analyzed by proton nuclear magnetic resonance ( 1 H-NMR) and differential scanning calorimetry (DSC), respectively. The results showed that the branching ratio decreased as the number of arms increased. The epoxide groups of the GMA units were kept intact during ICAR ATRP. Rheological, mechanical tests and dynamic mechanical analysis revealed that star poly (BA- co -GMA)/diglycidyl ether of bisphenol A (DGEBA) epoxy resin formulation exhibited better processability, higher impact resistance and thermal resistance than those of linear poly (BA- co -GMA)/DGEBA epoxy resin formulation.