Toughening of Epoxy Resin through Mechanical and Thermal Treatments

Tensile strength of epoxy resin specimens subjected to various mechanical and thermal treatments was studied: The mechanical treatment was imposition of finite tensile strains in either glassy or rubbery state and the thermal treatment was annealing or quenching. Specimens quenched from 180°C (> the glass transition temperature) were the most ductile, whereas specimens strained at 180°C and subsequently quenched were a little less ductile than the specimen quenched only. Fully annealed specimens showed the least ductility. Specimens strained at 140°C (< the glass transition temperature) and quenched were more ductile than the fully annealed specimens, yet less ductile than the specimens strained at 180°C and quenched. The variation in ductility of the specimens was discussed in terms of the degrees of their thermodynamic structural equilibrium and storage of strain energy caused by the mechanical and thermal treatments.