Barrier properties of biodegradable composite films based on kappa-carrageenan/pectin blends and mica flakes

In this work, the enhancement of the barrier properties to water vapour and gases (CO2 and O2) of a polymeric matrix composed by kappa-carrageenan and pectin (66.7% kappa-carrageenan), with the inclusion of mica flakes, was studied. The effect of the films mica content on the water vapour permeability (WVP) was dependent on the driving force applied. A higher WVP reduction (of about 40% for a mica content of 10%, mass of mica per mass of dry polymer), was observed when the films were more homogenously hydrated throughout their thickness. A significant decrease was also observed for both CO2 and O2 permeabilities (73% and 27%, respectively), in conditions where the films were plasticized with water (25% of water, dry basis), for which there is a depletion of the good barrier properties characteristic of dry polysaccharide films. In addition, the composition of 10% of mica flakes in the polymer matrix represented a critical volume fraction of inorganic particles, above which there was a decrease of the films barrier properties, for all components tested.