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

Abstract

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.

Influence of Low‐Molecular‐Weight Diamines in the Direct Imidation of Poly(propylene)‐Grafted Maleic Anhydride by Melt Reaction

“…This is an indication of the mixed grafting of amide‐imide groups. Maleic anhydride and primary amine can react easily to form amide and imide groups, the former product is a fast reaction, however the imidization process needs the removal of the condensed water to be completed 17, 37. In our study, water side‐products were not removed during the reactive mixing, and consequently, the grafting procedure of diamines did not result in a complete imidized grafting.…”

“…Maleic anhydride and primary amine can react easily to form amide and imide groups, the former product is a fast reaction, however the imidization process needs the removal of the condensed water to be completed. [17,37] In our study, water sideproducts were not removed during the reactive mixing, and consequently, the grafting procedure of diamines did not result in a complete imidized grafting. Due to C --O stretching, the absorption peak at 1 705 cm À1 in all PP-g-NH 2 spectra could have resulted from the overlapping of the absorption peaks of the amide (1 710 cm À1 ) and imide bonds (1 700 cm À1 ).…”

Improvement of adhesion between poly(ethylene terephthalate) and polyethylene

“…However, these polymers are not compatible and do not adhere to each other, because PE does not 408 H. Durgun and G. Bayram have any specific interacting group [2 -7]. Weak interaction at the PET-PE interface results in poor interfacial adhesion and reduces the performance of multilayer films [8].…”

“…De Gooijer et al [8] studied the interfacial adhesion between layers of HDPE and PET using maleic anhydride (MA)-grafted HDPE as the adhesion promoting agent. Bergstrom [9] examined the interaction of PET with silane-modified PE.…”

Surface analysis of aminated polypropylene films as an adhesion promoter to polycarbonate film

“…Primary amines are very attractive groups to be grafted to PP, but monomers containing primary amines are rarely used to make functionalized PP with primary amine (PP‐ g ‐NH 2 ) 13. An alternative method is reacting nucleophilic bifunctional compounds with carboxylic acid or maleic anhydride groups grafted into polymer 14–20. The reaction between these groups produces amide or imide bonds, leaving a polymer with pendant amine group 21.…”