The effect of interfacial interaction contribution to the mechanical properties of automotive topcoats

The studies described herein, relate to the nature of interactions in assembled coatings containing an alumina filler that has been coated with different chemical agents. The continuous medium is an automotive acrylic-melamine topcoat. The approach taken involved ultimate tensile strength evaluations and rheology studies. In general, it was found that there is a strong correlation between the ultimate tensile properties and both the alumina loading level and the nature of the surface treatment given to the alumina particles. Functionalization of the alumina with agents, to give apolar characteristics resulted in deterioration of the composite. Alumina particles with polar surface treatments gave an interaction with the matrix that improved the mechanical performance of the system. This improvement was attributed to the role of the Lewis acid–base interactions. The rheological studies and subsequent calculations show that, at the dispersion stage, the apparent thickness of adsorbed polymer layer varied with the nature of the surface of alumina. The adsorbed layer had an intermediate thickness for the dispersions containing the polar alumina. This thickness for the systems containing apolar alumina and untreated alumina was the greatest and the least, respectively.