Permeation of Oxygen and Moisture through Vacuum Web Coated Films

Abstract

Worldwide 15,000 km2 of polymer films are vacuum web coated with inorganic layers per year. Two third of these coatings are used by the packaging industry. Coatings drastically improve the barrier of polymers against the permeation of gases, moisture and flavor. For final packaging applications, coated layers are normally protected by laminating to another film. On laboratory as well as industial scale, the influence of various production parameters on the permeation through coated barrier films and final high barrier laminates was studied by using different types of substrate films, different kinds of pretreatment, different inorganic coating materials anddifferent lamination adhesives. The different substrate films, as biaxially oriented polypropylene (BOPP), polyethylene-terephthalate (PET) and ethylene-tetrafluoroethylene-copolymere (ETFE), were either pretreated at the film production site by a standard Corona atmospheric plasma or in-situ before the vacuum web coating by an oxyge n low pressure plasma. These films were vacuum web coated with aluminium (Al), aluminium oxide (AlOx) or silicon oxide (SiOx) and laminated against BOPP or polyethylene (PE) films using polyurethane and ORMOCER adhesives.Finally, different mechanisms for the permeation of oxygen and moisture through films with an inorganic barrier layer could be identified. Thereby, the barrier layer itself as well as substrate surface and adhesive layers adjacent to it determine the permeability through the final laminate