Factors affecting adhesion to polyolefins

Factors affecting the adhesion of paint to polyolefins have been studied. These include solvent pre-treatment, types of primer and their method of interaction, flame treatment and the addition of a surface migratory additive to the polyolefin. Surface analysis techniques X-ray photoelectron spectroscopy (XPS), attenuated total reflection infra-red spectroscopy (FTIR-ATR) and contact angle measurements were used along with electron microscopy, diffusion measurements and a lap shear test. Sol vent treatments were found to affect the topography of surface, as determined by atomic force microscopy, this causes a reduction in the receding contact angle of water indicating a reduced tendency for the coating to de-wet. This gives a greater joint strength. In the case of chlorinated polyolefin primers it has been shown that chain entanglement at the polymer/primer interface is an important factor determining the joint strength and can account for up to 50% of the strength in the systems studied. Chemical interaction between the polyolefin and the paint produced after flame treatment of the polyolefin improves adhesion. Factors determining migration of additives to the polymer surface have been studied. Surface migratory material has been identified but formation of weak boundary layers can lead to little or no improvement in adhesion properties. Further work is needed in this area.