CRYSTALLINITY OF POLY(ARYL ETHER ETHER KETONE) BY VIBRATIONAL SPECTROSCOPY

Medium infrared spectroscopy has been used by several authors to obtain the degree of crystallinity of PEEK films. The IR absorption bands at 947 and 966 cm-1, proposed by Jonas et al. are crystalline-sensitive. They appear as shoulders located in the neighborhood of other very intense absorption bands, and their deconvolution is difficult and sometimes hazardous for samples having a low crystallinity. In this same medium infrared region, designed hereafter as MIR, an additional band at 968 cm-1, appearing as a shoulder, is reported for the first time. The absorbance of these bands at 947 and 965 cm-1 does not approach zero for a density equal to the amorphous density. The analysis of the far infrared (FIR) spectrum of amorphous and partially crystalline PEEK films have indicated two 'crystalline-sensitive'' bands at 218 and 303 cm-1, one ''amorphous-sensitive'' band at 410 cm-1, and an internal band at 272 cm-1. The integrated absorbance of the crystalline and amorphous-sensitive bands have been correlated to the macroscopic density and the crystallinity of the films. The presence of crystalline- and amorphous-sensitive vibrational bands in the FIR spectrum of PEEK allows us to use the method proposed by Hendus et al. These FIR measurements have been interpreted on the basis of a two-phase model, and no experimental evidence has been observed for a third additional phase.