Flexibility improvement of epoxy resin by chemical modification

Epoxy resin was chemically modified with carboxyl-terminated poly(ethylene glycol) adipate (CTPEGA) and the modified epoxy networks were made by curing with an ambient-temperature hardener. The modified epoxy networks containing various concentrations of CTPEGA were characterized for their tensile, flexural and impact properties. It was observed that the mechanical strength gradually decreases and the strain increases with increasing CTPEGA concentration. However, the toughness and impact strength gradually increase with increasing CTPEGA concentration, attain a maximum and then decrease. The optimum CTPEGA concentration was found to be 20 phr. Fracture surface analysis by scanning electron microscopy indicates massive plastic deformation in modified networks. (C) 2004 Society of Chemical Industry.