ON CRYSTALLIZATION, MORPHOLOGY AND RADIATION EFFECTS IN POLY(ETHER ETHER KETONE)

The effects of high energy electron radiation on poly(ether ether keto ne) (PEEK) have been investigated by differential scanning calorimetry (d.s.c.), transmission electron microscopy (TEM) and solvent extracti on. It has been shown by extraction that irradiation results in the fo rmation of crosslinks which affect the crystallization and reorganizat ion kinetics and disrupt crystal structures. The d.s.c. behaviour is d escribed in terms of two regimes: up to similar to 66 MGy the observed effects principally result from changes in the amorphous regions, whe reas at higher doses crystal destruction appears to become increasingl y important such that by 260 MGy only a small residual melting peak is observed. This characteristic radiation response can be employed as a n expedient to prevent molecular reorganization without extensively di srupting the lamellar population. In this way the d.s.c. behaviour of PEEK has been studied in the absence of complications caused by anneal ing. It is shown that although some reorganization does normally occur , the high temperature melting endotherm is not purely an artifact of the experimental procedure. TEM examination reveals well-defined lamel lar morphologies, even in specimens that have been irradiated to such a level that little or no d.s.c. endotherm remains. Despite the absenc e of a distinct d.s.c. melting transition, the morphology of such samp les changes dramatically on heating to above their nominal melting tem perature.