Investigation of the “Surface” and “Interphase” Composition of Adhesion Promoter/Thermoplastic Olefin Systems: The Effect of Adhesion Promoter Bake Temperature

The interfacial chemistry of model systems consisting of two adhesion promoting primers and a single Thermoplastic Olefin (TPO) substrate was examined. Two commercial adhesion promoter (AP) materials were applied to a commercially-available TPO material and either flash dried at room temperature or baked at 100°C. The surface composition of the AP films and TPO substrate, and the interfacial compositions of the AP/TPO systems were characterized using x-ray photoelectron spectroscopy (XPS). The AP films studied were based upon a chlorinated polyolefin (CPO). For one adhesion promoter film (AP-1), no chlorine was present at the surface suggesting a nonhomogeneous system. For the second adhesion promoter film (AP-2), the surface composition was about 15% CPO and 85% AP matrix. No changes in AP surface composition were evident for the different bake conditions for either AP. Interfacial compositions of the room temperature flashed materials were found to be very similar for both AP/TPO systems, with CPO being present for each and at similar concentrations. Interfacial compositions for the baked materials were also similar for the two systems, although the level of CPO at the interface increased for both the AP-1 and AP-2 relative to the unbaked materials. The relative increases observed were 46% and 41% for the AP-1 and AP-2 systems, respectively. The increase in the relative concentration of CPO at the interface with bake temperature suggests that there is a stronger interaction between the AP and TPO. The implication of these data is that a baked AP should result in a more robust paint system with respect to AP/TPO adhesion.