Bi-layer materials based on thermoplastic corn starch, polylactic acid and modified polypropylene

Currently, the development of environmentally friendly materials with suitable properties for industrial use has become of great importance. In this work, bilayer materials were developed by assembling thermoplastic- corn starch monolayers (TPS) combined with semi-crystalline polylactic acid (PLAs) monolayers and maleic anhydride grafted polypropylene (PP_MA). The presence of a potassium sorbate solution was evaluated as interface material. Structural properties (FTIR and SEM), interactions with water (water vapor transmission rate, solubility in water and moisture content) and biodegradation of the materials were evaluated. The study showed that potassium sorbate promotes physical and chemical interactions between the monolayers studied. Furthermore, using a PLAs or PP_MA monolayer greatly solves the water vapor permeability and sensitivity to liquid water that starch-based materials present. This result is interesting since the addition of an adhesive material to assemble the low chemical affinity monolayers would be avoided. The developed materials exhibit great potential for application as packaging in the food industry.

Keywords: bilayer films, interfacial agent, physicochemical properties, biodegradation.