Mechanical characterization and morphology of carboxyl randomized poly(2-ethyl hexyl acrylate) liquid rubber toughened epoxy resins

A family of carboxyl randomized poly(2-ethyl hexyl acrylate) (CRPEHA) liquid rubbers which are 2-ethyl hexyl acrylate–acrylic acid copolymers (LR-1 to LR-4) with different carboxyl functionality were synthesized. The liquid rubbers were characterized by nonaqueous titration, vapor pressure osmometry (VPO) and solubility characteristics. All the liquid rubbers were reacted with the epoxy resin in 10:100 weight ratio using tri-phenyl phosphene (TPP) as a catalyst. The modified epoxy networks were made by reacting the homogeneous, prereacted resin with an ambient temperature curing agent. The effects of functionality of the liquid rubbers and ductility of the matrix, on the mechanical properties of the modified networks were investigated. The results were explained in terms of morphology observed by SEM. There is an optimum functionality which leads to best impact performance.