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

A range of thermally annealed isotropic and uniaxially drawn PEEK film s were examined using polarized Fourier transform Raman spectroscopy i n an attempt to obtain useful quantitative correlations with crystalli nity. 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 pre diction of ca. 2.4% crystallinity. Both approaches show potential for measurement of crystallinity in both isotropic and oriented samples us ing just one correlation model. A previously suggested crystallinity i ndex (the ratio of the 1600 and 1610 cm-1 band intensities) failed to give a satisfactory correlation for either sample set. It was also sho wn that the ratio of the 1146 cm-1 band intensities measured with the laser polarized perpendicular and parallel to the draw direction corre lates with the sample birefringence.