Enhanced Barrier Properties of Renewable Multiphase Polymer Coatings and Films

Abstract

The use of traditional synthetic polymer in the food industries imposes great sustainability issues in conjuncture with plastic waste accumulation and consumers’ health concerns. This drives innovation in bioplastics with acceptable physical properties. However, most single-phase biodegradable and bio-based bioplastics typically have poor moisture or oxygen barrier properties or both than traditional fossil fuel-based plastics, making it a challenging task to replace these plastics. This thesis presents multiple robust approaches to fabricate sustainable food packaging films and coating materials, considering various stratagems to combine different renewable components to enhance barrier properties. The use of multiphase systems, including blends, multilayer assembly, and nanocomposites as well as the employment of novel compatibilization techniques, such as surface modifications and emulsion stabilizations, are evaluated to fabricate the new generation of sustainable multiphase packaging materials. The first part of the thesis is on multilayer film systems made from two poly(lactic acid) (PLA) layers and one center thermoplastic starch (TPS) layer embedded with nano-clay. Maleic anhydride (MA) modification enhanced the interaction between each layer. This multilayer film assembly provided 92.4% improvement in moisture barrier compared to TPS films and 3300% improvement in oxygen barrier properties compared to PLA. The second part of the thesis has focused on fabricating Pickering emulsion-based coatings made from cornstarch and beeswax (BW) stabilized with modified cellulose nanocrystals (CNCs). Different fruits were dip-coated with a formulated edible coating, which displayed magnificent color and freshness preservation by reducing oxygen activities and preventing moisture losses. These preliminary findings show a promising outlook in food packaging and coating applications.