Surface depth-profiling of polymer compounds using step-scan photoacousticspectroscopy (S-2 PAS)

Depth-profiling of talc/polypropylene (PP) compounded polymers with 5, 10, 15 and 20% talc weight percents were examined to delineate concentration ef fects on surface stratification. This was achieved by utilizing step-scan p hotoacoustic spectroscopy (S-2 PAS) phase analysis to discriminate molecula r concentration changes for each species across a distance of 9 mu m from t he sample surface. From phase analysis results, it was determined that not only does talc lie 1-2 mu m closer to the surface than PP, but a layering e ffect results from an increase in talc concentration. This layering effect results in depths 0-3 mu m becoming saturated with talc molecules at lower talc concentrations, and layers 3-9 mu m showing evidence of saturation at higher concentrations. At these higher concentrations and greater depths, i t is postulated that PP is displaced by talc molecules giving rise to a bou ndary layer consisting mostly of talc. (C) 2000 Elsevier Science Ltd. All r ights reserved.