Annealing studies on a fully cured epoxy resin: Effect of thermal prehistory, and time and temperature of physical annealing

The dynamic mechanical behavior at about 1 Hz of a fully cured epoxy resin (maximum glass transition temperature, T g ∞ , ca. 170°C) ahs been studied during and after isothermal annealing in terms of the influence of thermal prehistory, time of annealing, and temperature of annealing ( T a ). Annealing temperatures ranged from T g − 15 to T g − 130°C. The rate of isothermal annealing was observed to decrease by a decade for each decade increase of annelaing time when the material was far from equilibrium. Annealing at high temperatures did not measurably affect the mateiral properties during cooling (for T ≪ T a ); similarly the effect of annealing at low temperatures was not measurale during heating (for T ≫ T a ).