In cooperation with the Leibniz Institute of Polymer Research and FILK (research institute of leather and plastic sheeting), we investigated the causes of weakening of paint adhesion on PP materials in connection with the additives contained in the plastic. In the process, different cleaning and activation processes were considered as well as their effect on the quantities of the additives on the plastics surface.
Polypropylene (PP)-based plastics are widely used in the automotive industry, among others, for reasons of weight reduction. For decorative applications, high-quality coatings are applied to PP add-on parts. Despite high production standards, adhesion problems occur time and again. It is known that the efficiency of typical cleaning and activation processes (powerwash, CO2 snow blasting, flame treatment, plasma treatment and fluorination) has a major impact on paint adhesion. In the past, little or no research had been carried out on the influence of plastic additives, which can migrate to the surface after a pre-treatment process. We used our expertise in chemical analysis to determine the critical quantities and compositions of additives on the surface of the material. In practical tests by means of steam jet testing and combining high mechanical stress with elevated temperatures, we evaluated the adhesion of coatings on samples pretreated in different ways after pre-damaging a small area with a cross-cut. By correlating the quality of adhesion with the analytically determined quantity and composition of the additives on the substrate surface, we were able to derive optimization measures for pre-treating the PP moulded parts.
German Federation of Industrial Research Associations AiF (through Forschungsgesellschaft für Pigmente und Lacke e.V. FPL / Federal Ministry for Economic Affairs and Energy (BMWi))
Dr. rer. nat. Katharina Weber, Dr. rer. nat. Volker Wegmann
Abteilung Beschichtungssystem- und Lackiertechnik Gruppe Analytik und Stoffprüfungen