Multinanolayered PA6/Cloisite and PE/PA6/Cloisite composites: Structure, mechanical and barrier properties

Economic and environmental challenges are driving development towards more efficient and lighter materials. Polyethylene (PE) and polyamide (PA6) are among the most used polymers and their assembly in multilayer make them efficient protective materials. The aim of this work is to design new multilayer composite films based on polyethylene and polyamide with high barrier properties. A coextrusion process with layer multiplier elements (LME) made it possible to carry out 100 μm-thick multilayer films containing 5 up to 1025 layers. Loaded PE/PA6 multilayer films were made by incorporating Cloisite particles (organo-modified montmorillonite – C30B) at 5 wt% into the PA6 layers. For comparison PA6 films with and without fillers were also made by using the same coextrusion process. The structural and thermal properties of all multilayer films were correlated with the water and gas barrier properties. A good dispersion of exfoliated C30B in the PA6 phase was observed even for the thinnest confined layers of PA6 in PE/PA6 multilayers (∼90 nm). We showed the complexity of the multinanolayer structures involving interphases as well as the complexity of the transfer mechanisms. The serial model used for predicting permeability highlighted some significant improvements of the gas barrier properties of confined PA6 layers. The barrier effect on all the multilayer films was, however, limited due to the "on-edge" orientation of the crystalline phases and structural defects induced during the coextrusion process. Despite this, the confinement of nanofillers in PA6 multilayers and in PA6 layers of PE/PA6 multilayers allowed to increase the barrier properties of multilayers.