Attenuated total reflectance Fourier transform infra-red studies of crystalline-amorphous content on polyethylene surfaces

Abstract Intensity ratios of the bands due to CH 2 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 FT i.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.