Abstract The replacement of petroleum-based plastics with sustainable, biodegradable alternatives is a key challenge in the transition toward a circular economy. Zein, a maize-derived protein, is a promising candidate for biodegradable thermoplastics, but its limited ductility and processability have hindered wider adoption. This study addresses this gap by exploring the effect of apricot shell flour (ASF) on zein (ZEI) thermoplastic materials plasticized with 25 wt% diethylene glycol (DEG) and processed by extrusion and injection molding. To date, the use of DEG as a plasticizer for zein in thermoplastics and the incorporation of ASF as a synergistic filler–plasticizer in such systems have not been reported, defining the novelty of this work. Mechanical analysis revealed an outstanding ductility. ZEI-DEG exhibited a strain at break of 57.2%, which was increased to 119.2% with 15% ASF, while impact strength rose from 6.4 to 15.9 kJ/m², confirming a synergistic plasticization effect between DEG and ASF. A decrease in glass transition was observed by dynamic mechanical thermal analysis with the incorporation of ASF, probably due to the interaction of uronic acids present in ASF with DEG and zein through hydrogen bonding. Morphology analysis showed good filler dispersion and good compatibility with the zein matrix. Thermogravimetric analysis (TGA) revealed a slight decrease in thermal stability with ASF, but materials remained stable up to 350 °C. Materials exhibited a progressive darkening with dark brown colors, providing a wood-like appearance that is potentially attractive for sustainable wood plastic composite applications such as packaging. The properties of these materials were far higher than the traditionally glycerol-plasticized zein materials. Overall, these findings highlight ASF as a promising bio-based filler that enhances flexibility and toughness of thermoplastic zein while maintaining good thermal behavior and creating aesthetically appealing natural composites. These green materials offer significant potential for biodegradable food packaging, furniture, and interior design products.
Peñafiel-Alvarado et al. (Fri,) studied this question.