Migration of low molecular weight moiety at rubber–polyurethane interface: An ATR-IR spectroscopy study

In this study, a novel approach based on ATR-IR spectroscopy consisting in the combined use of two prisms of different nature and refraction index (germanium—about 1 μm depth and zinc selenide—about 3 μm depth) was proposed to study the polyurethane–rubber interface. More precisely, the migration of paraffin wax additive in as-received and MEK cleaned vulcanized styrene–butadiene rubber (SBR)–polyurethane coating interface was monitored. Polyurethane coating with thickness of about 2 μm was applied on the SBR rubber surface and the ATR-IR spectra were recorded in the polyurethane coating. Thus, the ATR-IR spectrum obtained with Ge prism analyzed only the polyurethane coating whereas the ATR-IR spectrum obtained with ZnSe analyzed both the polyurethane coating and the near surface SBR. The results obtained showed that the paraffin wax migrated from the SBR rubber bulk to the rubber–polyurethane interface, then diffused into the polyurethane and finally migrated to the polyurethane surface.