THE FRACTURE-BEHAVIOR OF PHENOLPHTHALEIN POLYETHER ETHER KETONE AT ELEVATED-TEMPERATURE FOR LONG TERMS

The fracture behavior of phenolphthalein polyether-ether ketone (PEK-C ) affected by physical aging at 200 degrees C was studied by tensile e xperiments, scanning electron microscopy, and differential scanning ca lorimetry observations. The ductile-brittle fracture transition (DBT) caused by physical aging can be considered as a competition between fr acture mechanisms of crazing and shear yielding. The aging time requir ed for the DBT is found to be around 400 h, based on the morphological studies and tensile experiments. The shear yielding component of the mechanical deformation could erase the aging effect, thus a deaging ph enomenon occurs. We found that the deaging phenomenon has an intrinsic relationship with the extent of aging in the specimen and as a result of the fracture behavior. (C) 1995 John Wiley and Sons, Inc.