ATTENUATED TOTAL REFLECTANCE FOURIER-TRANSFORM INFRARED STUDIES OF CRYSTALLINE AMORPHOUS CONTENT ON POLYETHYLENE SURFACES

Intensity ratios of the bands due to CH2 bending and rocking normal vibrations, used as a measure of the surface crystallinity in polyethylene, are examined by attenuated total reflectance Fourier transform infra-red (ATR FTi.r.) spectroscopy. This study shows that the ATR optical dispersions and the orientation of surface crystallites have a substantial effect on the crystallinity measurements. It appears that improper analysis of strong, overlapping i.r. bands in the ATR spectra may generate systematic errors. While the optical effects associated with ATR measurements can be accounted for and corrected by the use of the Kramers-Kronig transform and Fresnel's equation, determination of the crystallinity gradients and orientation of the crystallites requires detailed polarization studies and theoretical considerations.