The onion principle

A novel approach to increasing the gas barrier of plastics is described that follows a natural principle found in the structure of an onion. The effect is based on raising the numbers of boundary layers that have to be penetrated by permeating substances. In tests the reduction in oxygen permeability of film composites that were entirely comprised of PET could be demonstrated. Large scale implementation in packaging solutions for food products can be achieved via bonding, thermal lamination or coextrusion. However it is vital to ensure that boundary layers are still present. The benefit lies in extending product shelf life with improvements to the recyclability in comparison to multi-layer constructs from various materials.