MEASUREMENT OF POLY(ARYL ETHER ETHER KETONE) CRYSTALLINITY IN ISOTROPIC AND UNIAXIAL SAMPLES USING FOURIER-TRANSFORM RAMAN-SPECTROSCOPY - A COMPARISON OF UNIVARIATE AND PARTIAL LEAST-SQUARES CALIBRATIONS

A range of thermally annealed isotropic and uniaxially drawn PEEK films were examined using polarized Fourier transform Raman spectroscopy in an attempt to obtain useful quantitative correlations with crystallinity. Both univariate (carbonyl stretching wavenumber measurement) and multivariate (partial least-squares) calibrations were found to give good correlations, in the latter case yielding a standard error of prediction of ca. 2.4% crystallinity. Both approaches show potential for measurement of crystallinity in both isotropic and oriented samples using just one correlation model. A previously suggested crystallinity index (the ratio of the 1600 and 1610 cm-1 band intensities) failed to give a satisfactory correlation for either sample set. It was also shown that the ratio of the 1146 cm-1 band intensities measured with the laser polarized perpendicular and parallel to the draw direction correlates with the sample birefringence.