Physcial Modifications of Propylene /Ethylene-Propylene-Diene-Monomer Rubber Surfaces. I. Determination of Surface Composition and Surface Order by Fourier Transform Infrared-Attenuated Total Reflectance

The aim of this study was to introduce a new method for determining the surface composition and surface order of PP/EPDM (propylene/ethylene-propylene-diene-monomer rubber) blends, based on surface-enhanced infrared spectroscopy. PP/EPDM blends were characterized by Fourier transfer IR-attentuated total reflectance (FTIR-ATR) using two different internal reflection elements, Ge and KRS-5. These elements provide information at different depths and show differences in relative band intensities. A linear relationship between the ratio of the bands at 2850 and 2920 cm exp -1 and EPDM content was obtained when well-defined compositions of PP and EPDM mixtures were used. Changes in crystallinity were measured by the ratio of the bands at 2959 and 2951 cm exp -1 . For comparison, bands in the lower region of the spectrum and DSC and WAXS measurements were used. It was shown by two calibration methods that FTIR-ATR can provide information on surface composition and surface crystallinity at very low penetration depth. This new method indicates that injection-molded samples show a lower surface order and lower EPDM content at the surface than is seen in bulk.