Surface depth-profiling of polymer compounds using step-scan photoacoustic spectroscopy (S2 PAS)

Depth-profiling of talc/polypropylene (PP) compounded polymers with 5, 10, 15 and 20% talc weight percents were examined to delineate concentration effects on surface stratification. This was achieved by utilizing step-scan photoacoustic spectroscopy (S2 PAS) phase analysis to discriminate molecular concentration changes for each species across a distance of 9 μm from the sample surface. From phase analysis results, it was determined that not only does talc lie 1–2 μm closer to the surface than PP, but a layering effect results from an increase in talc concentration. This layering effect results in depths 0–3 μm becoming saturated with talc molecules at lower talc concentrations, and layers 3–9 μm showing evidence of saturation at higher concentrations. At these higher concentrations and greater depths, it is postulated that PP is displaced by talc molecules giving rise to a boundary layer consisting mostly of talc.