Innovative development and characterization of thermoplastic zein-based biopolymers for food packaging via injection molding

This study focuses on the development of biodegradable polymers using zein (ZEI) plasticized with glycerol (GLY) and urea (UREA), with the goal of replacing conventional plastics in food packaging. The optimized combination of glycerol and urea in zein formulations significantly enhances mechanical properties: ZEI-15GLY-10UREA formulation achieves a maximum tensile strength of 21.3 MPa. Elongation at break is higher in blends with lower urea content, reaching 9.1% in ZEI-20GLY-5UREA. Conversely, formulations with higher urea content exhibit reduced elongation and toughness, evident in the decrease to 1.8 kJ/m2 of impact energy in ZEI-25UREA. Samples show Shore D hardness values up to 82.0. Morphological characterization confirms consistent behavior with mechanical properties, indicating that the glycerol and urea combination promotes a more ductile structure. Incorporation of these plasticizers lowers the glass transition temperature of the compounds from 53.8 °C in ZEI-25GLY to between 48 °C and 49 °C in formulations with 5% and 10% urea. All formulations exhibit biodegradation behaviour, with all of them achieving complete degradation in the final weeks. In all cases, there is a clear trend of mass loss during the first 6 weeks, with all formulations losing more than 80% of their initial mass. [Display omitted] •Lower urea content increases elongation at break of zein thermoplastic materials.•Combination of urea and glycerol increases the ductility of zein materials.•15 wt% of glycerol and 10 wt% urea results in better overall properties.•Complete biodegradation is achieved by all urea-glycerol-zein materials.