The effect of plasticizers on properties of thermoplastic rice protein processed by extrusion and injection molding

The manufacturing of rice protein (RP) thermoplastic materials by combining it with urea, glycerol, sorbitol and xylitol by extrusion and injection molding techniques are studied in this work. Very promising protein-based sustainable polymeric materials are obtained, with tensile strength superior to 17 MPa in the case of samples plasticized with urea, which allows to obtain very rigid materials. On the other hand, the combination of RP and urea with glycerol, sorbitol or xylitol gives rise to materials with elongation at breaks superior to 40%. This means a wide range of properties depending on the combination of plasticizers used. Urea crystals finely embedded in the RP matrix are observed by microscopy analysis, which are confirmed by the presence of a melting peak in DSC at approximately 127 ºC. Chemical analysis also revealed the predominance of these urea crystals through chemical analysis. Dynamic-mechanical thermal analysis (DMTA) also showed the glass transition temperature (T g ) of the materials to be between 28 and 60 ºC, being the sample with glycerol the one with the lowest value. All materials were observed to be completely biodegradable at 3-4 weeks, gaining increasing environmentally friendly value. The plenty availability of rice protein makes these materials very attractive for producing environmentally friendly materials with great potential in the food industry. • Urea allows to obtain rigid rice protein thermoplastic materials. • Addition of alcohol-based plasticizers improves the ductility of rice protein materials. • Urea-rice protein thermoplastic materials prove to be completely biodegradable. • Urea crystals are maintained in the rice protein thermoplastic polymers’ structure.