Structure and Barrier Properties of Biodegradable Polyhydroxyalkanoate Films

Abstract

The water vapor sorption and permeation to water and gas molecules of films prepared from industrially available polyhydroxyalkanoates (PHAs) were analyzed in detail. Two film-forming processes were compared through their transport properties. The presence of additives, which can alter the barrier properties of films, was highlighted in some commercial-grade PHAs by investigating the physicochemical properties of these films. The water vapor sorption results were simulated using the appropriate Park model, highlighting the moisture resistance, the entrance of water molecules into films, and the impact of the process used and were then discussed through the analysis of diffusion coefficients. A significant reduction in water permeability was evidenced with the increase of degree of crystallinity of the biopolyesters. Water diffusivity was found to be dependent on water concentration and this was due to the plasticization effect induced by water molecules. In terms of gas permeation, a singular behavior peculiar to these PHA films was revealed showing a potential interest for packaging or biomedical applications.