Optimization of Processing Conditions for Rice Bran-based Bioplastics Through Extrusion and Injection Molding

Conventional plastics pose environmental threats due to their non-biodegradable nature and their reliability on fossil resources, leading to the exploration of sustainable alternatives. In this sense, biodegradable bioplastics derived from renewable resources offer a promising solution to mitigate ecological impacts. This study focuses on the combination of extrusion and injection molding for the development of rice bran-based bioplastics. Being a by-product from the rice industry rich in starches and proteins, rice bran is an abundant and non-expensive resource that contributes to an enhanced waste management and represents a step forward in integrating the principles of a circular economy. This study delves into the optimization of processing conditions through a Design of Experiment approach. For this purpose, the number of extrusion steps, cylinder and mold temperatures, and injection pressure were investigated. The results showed that two extrusion steps led to a significant increase of approximately 22.8% in Young’s modulus and 37.5% in tensile strength compared to a single extrusion cycle. This enhancement was attributed to the facilitation of starch gelatinization and biopolymer-plasticizer interactions (achieving thermoplastic starch and protein plasticization). Similarly, manipulation of injection temperatures and pressure had notable effects on tensile properties, highlighting the complex interplay between processing parameters. In particular, when using cylinder and mold temperatures of 110 °C and 180 °C, respectively, along with 800 bar, it was possible to achieve a further enhancement in tensile properties, with an increase of 97.1% in Young’s modulus and over 100% in tensile strength. Overall, this research underscores the importance of understanding the relationship between processing conditions and biopolymer interactions for bioplastic production.