Exploitable results ENHANCED WETTABILITY AND ADHESION OF POLYMER FILM SURFACES BY ELECTRICAL DISCHARGES IN SILANE GAS MIXTURES UNDER ATMOSPHERIC PRESSURE; HIDYNE The HIDYNE project had focused on a new surface treatment of polyolefin films and more particularly of Bi-Oriented Polypropylene films (BOPP) with the objective to obtain high and permanent surface tension levels for improved wettability and adhesion. The new treatment consists on the replacement of air, in the electrical discharge area, by a gaseous mixture based on nitrogen and small amounts on silane with an oxidising gas, at one atmosphere pressure. The process is then suitable for continuously running converting lines. In terms of surface modification the use of a nitrogen/silane/oxidant mixture leads to the deposit of a thin silica, SiO2, layer onto the film surface as evidenced by ESCA and AFM measurements. This silica layer is highly wettable and surface tensions of up to 72 mN/m were obtained for BOPP with excellent stability over time (more than 12 months stability was measured). The modified surface is composed by siloxane, Si-O-Si, and silanol Si-OH groups, which confer to it an amphiphilic character, allowing efficient wetting by both solvent based and water based ink or lacquer formulations. This silica modified surface is washable, i.e. the silica layer is not removed when washing the film with water. This was verified by ESCA and AFM measurements before and after washing. In addition, the presence of silanol functions induces easy hydrogen bonding formation with water molecules, thus conferring to the treated material anti-fog behaviour. The silanol functions are chemically reactive forming either hydrogen or covalent bonds with various functionalised resins. This leads to excellent ink and lacquer adhesion with nitrocellulosic, vinyl butyral, isocyanate and acrylic resins containing formulations. Despite the high surface tension levels obtained, friction coefficient is low (it corresponds to that of silica) and blocking, upon winding the film, does not occur. Finally, the thin layer silica deposit does not affect neither the optical, nor the mechanical properties of the treated substrate. In order to run the process an adequate treating station was designed and built. This station is composed by the main corona treater and electrical generators , a gas handling/mixing manifold, gas supply means, an off-gases treating unit, and a control/command unit, which allows easy operation of the whole system by means of a personal computer (PC). The treating station can be installed in-line or off-line, according to user requirements and it can run of up to 250m/min. Typical converting operations concerned by this new surface treatment process are lacquer lamination extrusion lamination, extrusion coating, printing, lacquering and metallisation. High product quality, flexibility, productivity increase, cost decrease and more respect to the environment are the main, direct impacts when adopting this silica surface coating technology Searching for OpenAIRE data... There was an error trying to search data from OpenAIRE No results available
