Toughening of epoxy resin by modification with 2-ethylhexyl acrylate-acrylic acid copolymers

2-Ethylhexyl acrylate–acrylic acid copolymers, ie carboxyl randomized poly(2-ethylhexyl acrylate) (CRPEHA) (LR-1 to LR-6), with different molecular weights and functionality were synthesized. The liquid rubbers were characterized by FTIR spectroscopic analysis, non-aqueous titration, vapour pressure osmometry (VPO) and viscosity measurements. All the liquid rubbers were reacted with the epoxy resin in 10:100 weight ratio using triphenyl phosphine as a catalyst. The modified epoxy networks were made by reacting the homogeneous prereacted resin with an ambient temperature hardener, triethylene tetramine (HY 951). The effect of the molecular weight and functionality of the liquid rubbers on the thermal and impact properties of the modified networks was investigated.