Water sorption and water vapour diffusion in food‐grade plastics packaging materials: Effect of a polymeric plasticizer

Abstract

AbstractIt is recognized that packaging has a profound effect on the ultimate quality of food products reaching the consumer. So, the selection of proper packaging materials has become one of the major problems of the food technologist. In the field of flexible packaging one of the most important properties is water vapour/package interaction. Inverse gas chromatography has been used to study water sorption of polyvinylchlor‐ide and poly(vinylidene chloride‐vinylchloride) plasticized with different amounts of a polymeric plasticizer (poly(adipate ester)) at temperatures between 25°C and 50°C. It was found that the specific retention volume of water increases with decreasing temperature and increasing amount of plasticizer into the polymeric mixtures. The effect of temperature on water sorption behaviour is more pronounced compared with that of plasticizer addition. The thermodynamic parameters of water/polymer interaction, namely free energy, entropy, enthalpy and activity coefficient were calculated. Values were interpreted on the basis of an active‐site absorption model. The Van Deemter equation was found to be applicable to these systems and was used to determine diffusion coefficients and activation energies for diffusion. Diffusion coefficient values increase with increasing amounts of plasticizer and this increase is accompanied by a decrease in the activation energy for diffusion.