The J-integral method was aPPlied to the amorphous poly (phenylene etherketone ) (PEK-C)

which is a high-Performance POlymer with Tg of 220 ℃ made inthis institutinn. The relationships between reta￣g take at temperature of 200 t withthe yield strength fracture toughness JIC critical plastic yielded zone size AL. andresistance to stable crack extension aJ/d(△a) of PEK-C were investigated. Withincreasing the retaining table at 200 t

a pronounced increases of the fold strengthand aJ/d(△a) occur within first a few hours and then only a slow asymptotic approach to equilibrium properties is observed. However the JIC and △LC decrease slowly with increasing the retaining time at 200℃. The time-dependence of yidlding and frac-ture behavior at the elevated temperature was discussed based on molecular motion.