Lamination of starch/polyesters by thermocompression for food packaging purposes

Multilayer films were obtained by thermocompression to design laminates with better fit food packaging requirements. Films of glycerol-plasticised corn starch, both non-modified and modified by dry heating (DH) or PHBV layers containing 0, 10 or 20% PEG 1000 were combined with amorphous PLA sheets. Combinations of starch-PLA-PHBV tri-layers were also obtained and characterised as to their functional properties for the first time. The surface tension of the different polymer films was determined to estimate the adhesion work ( W a ) of each polymer pair, which was compared to the experimental seal strength ( SS ). The analyses of the functional properties of the mono, bi- and tri-layers revealed a marked reduction in the water vapour permeability of starch films by DH modification while PEG weakened the strength of PHBV films and greatly increased their oxygen permeability. An overall improvement was observed in the functional properties of PLA-starch laminates with respect to the monolayers, although PLA-PHBV combinations and tri-layers did not offer great additional benefits as compared to the individual non-plasticised PHBV films. The interlayer migration of plasticisers, including the water present in starch films, altered the expected tensile and barrier properties of multilayers, which resulted in advanced materials with unique characteristics.