THE CRYSTALLINITY OF POLY(ETHER ETHER KETONE)

Differences have been observed between the enthalpies of crystallization and fusion of quenched 'amorphous' poly(ether ether ketone) (PEEK) which have been attributed to residual crystallinity produced during quenching. Comparison with samples of PEEK crystallized under well defined conditions reveals that these apparent differences arise from changes in the heat capacity of the crystalline solid and the liquid alone and there is no need to invoke abnormal crystalline structure, or the presence of residual crystallinity produced on quenching to explain the apparent differences. Comparison is made of the degree of crystallinity as measured by d.s.c., WAXS and density from which the enthalpy of fusion of totally crystalline PEEK at 437 K was determined to be 122.5 +/- 1.5 J g-1.