Infrared and Raman Analysis of In-Plane Microtomed Thermoplastic Olefins

The distribution of chemical composition of as-molded thermoplastic elastomers: polyolefinic (TEOs), commonly called TPO, has been studied. Fifty in-plane sections, each 10 μm thick, were microtomed from the surface to a depth of 510 μm into the sample. These sections were studied by transmission infrared to compare the level of polypropylene (PP) and polyethylene (PE) at the surface and throughout the 510 μm thickness. No compositional differences were observed. These same sections were studied by optical microscopy. Birefringent spherulites were observed beginning about 100 μm into the sample. Deeper into the sample, these spherulites became larger, approaching 20 μm. Infrared microscopy was used to analyze several 20 μm by 20 μm spots on these sections. Still no compositional difference could be found. A Raman microprobe using a 2 μm diameter sampling spot was also used to analyze these sections. Once again no compositional differences in the amount of PP and PE were observed at the surface as compared to 500 μm into the sample.