Precise and quantitative assessment of automotive coating adhesion using new microgap pull-off test

The quantification of coating adhesion on substrates is an important technology that has recently received much attention in automotive industry because the adhesion characteristics of automotive paints have a great influence on color and appearance of automobiles. Here, we present a robust and precise method for quantifying the coating adhesion of automotive paints on flat substrates using new microgap pull-off test based on the application of a micrometer-thick layer of adhesive to the divided compartments. The influence of water and organic material penetration on the coating adhesion between paint and plastic substrate is investigated in order to quantitatively measure the water resistance and organic compound resistance of automotive paints. When the paint absorbed moisture and organics, they penetrated through the paint surface to interfere with the coating adhesion between the plastic substrate and the paint layer, thereby reducing the initial coating adhesion. In addition, we investigated the effect of chlorinated polyolefin (CPO) content on the coating adhesion between nonpolar plastic substrate and polar paint coating. As the CPO content in polar acrylic paints increased, the coating adhesion of the polar paint to nonpolar plastics was increased due to the compatibilization effect of CPO resin in the coating interface.