EVALUATION OF X-RAY-EXCITED VALENCE-BAND MEASUREMENTS FOR THE DETERMINATION OF THE SURFACE-COMPOSITION OF MODEL THERMOPLASTIC OLEFINS

In this study we evaluate the utility of using x-ray-excited valence b and measurements for the determination of the surface composition of s imple model thermoplastic olefin systems composed of binary blends of semicrystalline polypropylene (PP) and an amorphous ethylene-propylene copolymer (Eco-P). Blend compositions included combinations of high-a nd low-molecular-weight (MW) PP and E-co-P composed of 60 wt.% PP/40 w t.% E-co-P and 80 wt.% PP/20 wt.% E-co-P blends. Results demonstrate t hat experimental valence band spectra for the polyolefin blends can be approximated by a linear combination of the pure-component valence ba nd spectra. Bulk compositions determined from spectra recorded from cr yomicrotomed cross-sections were found to be consistent with the bulk component wt%. The surface compositions of the binary blends were all found to be enriched in PP. Measurements taken from the 60/40 wt.% ble nds were 10-20% higher in PP concentration than the bulk compositions, and were found to vary depending on the MCV combination of the compon ents. No MW dependence was observed for the 80/20 wt.% blends, apparen tly due to a near saturation of the surface with PP. The development o f methods for assessing the surface composition of these types of mate rials may prove useful in monitoring changes in composition with mater ial formulation and process conditions. Information of this nature cou ld be helpful in permitting an evaluation of potential influences of c omposition on adhesion. (C) 1997 by John Wiley & Sons, Ltd.