Amine modified polyethylenes, prepared in near critical propane, as adhesion promoting agents in multilayered HDPE/PET films

High density polyethylene [HDPE] grafted with 0.13, 0.04 and 1.04 wt% maleic anhydride (abbr.: PEMA) was modified with an excess of a variety of diamines in near critical propane. The resulting amic acid groups were quatitatively imidized to the corresponding imide (PEMI) in the melt. Increasing the percentage maleic anhydride grafted on the HDPE resulted, upon reaction with the diamines, in an increased gel content, due to crosslinking. Three‐layered films were prepared using HDPE film and polyethylene dterephathalate (PET) film as the outer layers and the PEMAs and PEMIs as the inner layer. Adhesion strengths were measured using a T‐peel test. Increasing the bonding temperature resulted in an improved adhesion. The most optimal system for adhesion proved to be HDPE grafted with 0.40 wt% MA and modified with a pendent secondary amine group. For this system the lowest number of reactive amine groups was lost owing to crosslinking reactions, so the highest concentration of amines is available for interactions with the PET film. The absence of extensive HDPE crosslinking in addition implies a better flow of the adhesive layer during lamination. From contact angle measurements, it was observed for all samples that after delamination of the three‐layered system, PET was present on the PE‐surface and PE was present on the PET‐surface.