Lamination of starch/polyesters by thermocompression for food packaging purposes

Abstract

Multilayer films were obtained by thermocompression to produce laminates that better-fit food packaging requirements. Films of glycerol-plasticised corn starch, both non-modified and modified by dry heating (DH) and PHBV films containing 0, 10 or 20% PEG 1000 were combined in bilayer associations with amorphous PLA sheets. Starch–PLA–PHBV tri-layers were also obtained and characterised as to their functional properties. The surface tension of the different polymer films was determined to estimate each polymer pair's adhesion work, which was not well correlated to the experimental seal strength. DH starch modification markedly reduced (95%) the water vapour permeability (WVP) of starch films while PEG weakened the strength of PHBV films and greatly increased their oxygen permeability (OP). Lamination with PLA reduced (85%) the WVP of non-modified starch while increased the tensile strength (183 and 196%) and decreased the elongation at break (25 and 22%) of the non-modified and DH starch films. Nevertheless, PLA–PHBV laminates and tri-layers did not exhibit significantly improved properties as compared to the non-plasticised PHBV monolayers. The interlayer migration of plasticisers, including the water present in starch films, altered the expected tensile and barrier properties of multilayers.