PBAT/corn zein ester blends: Rheology, morphology, and physicochemical properties

The demands for sustainable packaging materials have increased interest in a new class of biomass-derived and biopolymers, such as zein protein, which are renewable, biodegradable, and water-insoluble, with excellent film-forming attributes and appealing barrier properties. However, the lack of mechanical robustness and low thermal stability of zeins impose a major limitation on their direct usage as packaging materials. As a result, extensive modifications, such as plasticization and incorporation of additives, are typically required to overcome the inherent deficiencies. In this study, corn zein was esterified to graft a fatty acid chain (decanoic acid) and blended with poly(butylene adipate-co-terephthalate) (PBAT) at varying weight ratios to produce mZein/PBAT blend films via a melt extrusion process. The blends' phase morphology, rheology, thermal, mechanical and barrier properties were investigated. The fatty acid grafting on zein enabled enhanced interfacial bonding between mZein and PBAT, promoting the compatibility of the two immiscible phases in the blends. Blending modified zein with PBAT yielded balanced stiffness, strength, and elasticity without needing external compatibilizing agents. Furthermore, the oxygen permeability of the blends was shown to reduce by up to 59% compared to neat PBAT, and water vapor barrier performance was improved by 68% compared to neat mZein. These new blended mZein/PBAT films have the potential to provide an eco-friendly material that can be used in consumer bags, packaging films, and agricultural mulch films.