Permeation of Oxygen, Water Vapor and Aroma Substances through Vacuum Web Coated Films
Due to the demand of the packaging industry for cost effective high barrier packaging materials, the amount of vacuum web coated films grows annually by 6 to 8 %. In spite of the high application rate of these films, little is known about the relevant permeation mechanisms. In terms of a quantitative prediction, the mechanism of the oxygen permeation is well understood, but not enough for the water vapor and especially not for the aroma permeability. For all different substances the barrier properties of the final laminate result from the synergetic effect between the vacuum web coated barrier layer and the polymer layers next to it. For a systematic investigation, BOPP films were vacuum web coated with Aluminum and silicon oxide on industrial scale. In the next step, the different films were laminated against BOPP by applying different types of polyurethane adhesive. The permeabilities of oxygen, water vapor and aroma substances through the non-coated, vacuum web coated and laminated films were measured. Comparing these results with the AFM (atomic force microscopy) analysis of the barrier layers, the most critical steps along the production chain can be identified for producing laminates that show a higher barrier against the different permeating substances.