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, Tg∞, 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 (Ta). Annealing temperatures ranged from Tg − 15 to Tg − 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 ≪ Ta); similarly the effect of annealing at low temperatures was not measurale during heating (for T ≫ Ta).