Influence of Polymer Film Surfaces on Adhesion and Permeation Properties of Vacuum Web Coated High Barrier Films and Laminates. Results of a Cooperative Research Project

By laminating vacuum web coated biaxially oriented polypropylene (BOPP) films against BOPP films, high barrier laminates can be achieved possessing an oxygen permentation lower than 2 cmü/m² d bar and a moisture permeation down to 0,01 g/m² d. The key issues along the whole production process to achieve results like these are: The surface properties of the non-coated films, materials and techniques of the coating, as well as the lamination step. In our investigation the influence of the surface properties of the non-coated BOPP films on the functionality - as adhesion and permeation - of coated barrier films and the final high barrier laminates was studied on the one hand by varying the surface of the BOPP basic films and on the other hand by various pretreatments of the different polymer film surfaces. The BOPP homopolymer or copolymer films were either pretreated at the film production by a standard Corona atmosphere plasma or in-situ before the vacuum web coating by an oxygen low pr essure plasma. The topography of the nontreated and pretreated films was analyzed by Atomic Force Microscopy (AFM) and the chemical properties by contact angle measurements as well as X-ray Photoelectron Spectroscopy (XPS). These BOPP films were vacuum web coated with aluminium (AI) or silicon oxide (SiOx) and laminated with a two component system, on lab as well as on industrial scale. Finally, metallized as well as transparent laminates with different surface properties before the coating and laminating were mechanically stressed and the changes in permeation are measured. Hence, typical surface properties of the non-coated films being necessary to get high barrier laminates after coating and lamination could be identified.