Permeation Processes through Vacuum Web Coated Films and Laminates

From the worldwide annual quantity of 15,000 km2 of polymer films that are vacuum web coated with inorganic layers, two third are used by the packaging industry. Although food packagings have the highest share, specialized technical packagings show an increasing fraction. For virtually all applications, the major function of the coatings is the drastic improvement of the barrier of polymers against the permeation of gases, moisture and flavors. Therefore, a proper understanding of the permeation processes is a key issue. On laboratory as well as on industrial scale, the influence of various production parameters on the permeation through coated barrier films and final high barrier laminates was studied by using different inorganic coatings materials and lamination adhesives. The substrate film, biaxially oriented polypropylene (BOPP), was vacuum web coated with aluminium (Al), or silicon oxide (SiOx) and laminated against BOPP films using polyurethane and ORMOCER. From the results, different mechanisms for the permeation of oxygen, moisture and flavor substances through films with an inorganic barrier layer could be identified. In the final laminate, the barrier layer itself as well as substrate surface and adhesive layers adjacent to it determine the permeability and thus the functionality of the product.