Femtosecond laser surface texturing of polypropylene copolymer for automotive paint applications

Over the past few decades, polymers have progressively replaced metals and metallic alloys in technological applications for which, for example, lightweight, cost-effectiveness, chemical resistance and flexibility for precision-machines components are needed. Furthermore, there is great attention in modifying polymeric surfaces through physical and/or chemical treatments. In this context, the aim of this study is the enhancement of polypropylene specific automotive applications by inducing changes into its surface morphologies. Laser surface texturing technique is of particular interest because of its ability in producing morphological and, consequently, physical and/or chemical modifications on polymer surface. A femtosecond Titanium:Sapphire laser source was employed in order to investigate any variation of surface properties due to the fine tuning of both laser pulse energy and focused laser beam distance from the sample target. The laser treated samples were studied by Scanning Electron Microscopy, ?-Raman spectroscopy and contact angle measurements. The morphological analysis showed that micrometric sized dimple- and groove-like structures were produced after laser irradiation, maintaining mostly unchanged the chemical features of polypropylene surface but changing its wetting properties. These findings have been successfully applied to activate polypropylene surfaces for subsequent painting processes in automotive industry demonstrating that the femtosecond laser surface treatment here studied is an alternative method to the commonly used flame treatments on automotive components improving the paint adhesion to the treated polypropylene surfaces.