Stratification processes in thermoplastic olefins monitored by step-scan photoacoustic FT-IR spectroscopy

In this study we utilized step-scan photoacoustic Fourier transform IR (SS-PA-FT-IR) spectroscopy to examine surface/interfacial properties of thermoplastic olefins (TPOs). This approach, combined with 2D FT-IR correlation analysis, allowed us to determine stratification processes in TPOs. These studies showed that the talc and polypropylene (PP) crystalline phase in TPO stratifies within the first 6–30 μm from the surface. Specifically, the PP crystalline phase exists at about 6.5 μm from the surface and its content diminishes at 7.1 μm, followed by reappearance around 11.3 μm, and becomes more prevalent upon approaching the bulk of TPO. Talc concentration levels show a similar pattern of change with depth across the interface, although absolute concentration levels differ from those of crystalline PP. These studies also demonstrated that SS-PA-FT-IR is a powerful tool in surface analysis, in particular for surface/interfacial analysis of multi-component polymeric systems.