Evaluation of Recyclable Multilayer Packaging Designs Utilising Controlled Interlayer Adhesion

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Background: The packaging industry is utilising increased levels of bio-based or recycled plastics and virgin plastic-based packaging is irreplaceable in more demanding applications such as food and pharmaceutical storage where different types of functional plastics are combined in a laminate form to produce multilayered packaging (MLP). Even though MLP are very effective in packaging applications, the typical multilayer format is a barrier to effective recycling, limiting the value and market for the use of recovered materials. Objective: This article investigates two new multilayer packaging design concepts which enable separation of the constituent layers in MLP. In these designs, the typical thermoset based adhesive layer in MLP is replaced by (i) localised adhesion by patterning surface treatments on the layers (no dedicated tie-layer) and (ii) by a water-soluble adhesive layer. Methods: T-peel testing is performed to evaluate the level of adhesion. The feasibility of these designs to enable layer separation was also investigated through representative tests that the simulated typical processes of shredding and washing in recycling streams. Results: The effectiveness of masks to localise surface treatment and thus create regions of higher and lower adhesion was captured in the peel test results for design A. The comparatively low levels of adhesion in design A enabled an easy separation of layers. An excellent adhesive was observed in peel test for design B with water soluble tie layer and the layers were separated by dissolving the tie layer in water. Conclusions: These concepts targeting the interface between MLP layers can be scaled with MLP complexity. Potentially, a combination of the two strategies could yield an optimal solution, where the total surface area of adhered MLP is reduced due to localised adhesion and a distinct water-soluble adhesive layer provides the necessary adhesive strength comparable to current MLP applications. Supplementary Information: The online version contains supplementary material available at 10.1007/s11340-025-01200-2.

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