Injection molding versus extrusion in the manufacturing of soy protein‐based bioplastics with zinc incorporated.

Bioplastics are mostly processed by injection molding. However, more continuous techniques are still being tested, such as extrusion, which allow them to be produced at a lower cost. In this way, the principal objective of this work was to develop soy protein‐based bioplastics with zinc sulphate (fertilizer) incorporated by extrusion, using different plasticizers (glycerol and water) and temperatures (95, 115, and 135°C). In addition, the same parameters were used to produce bioplastics by injection molding in order to compare both processing techniques. Thus, the main novelty of this work was the evaluation of extrusion as a substitute for injection molding in the production of these bioplastics, trying to improve their scalability to the industrial sector. For this, the bioplastics were evaluated through their physico‐chemical and mechanical properties, as well as functional properties for horticulture and microstructure. Results showed that glycerol allows obtaining better mechanical resistance but quickly zinc release. Nevertheless, these properties can be modified by the processing parameters, getting better mechanical resistance and slower zinc release at higher temperatures. In addition, results highlight the high potential of extrusion for the development of bioplastics, which can lead to a reduction in operating costs during industrial processing. [ABSTRACT FROM AUTHOR]