Effect of processing on the viscoelastic, tensile and optical properties of albumen/starch-based bioplastics

The development of biodegradable materials to be used by the plastic industry has been receiving increasing interest over the last few years. In this work, different blends of albumen protein and starch (potato and corn) have been used as raw materials for bioplastics exhibiting high transparency and a suitable mechanical behaviour. In order to study the effect of processing on the mechanical and optical properties of albumen/starch-based bioplastics, three different procedures were followed: (i) compression-moulding-based manufacture, (ii) extrusion, and (iii) combination of both. Dynamic bending (DMTA) and tensile tests, together with %-transmittance measurements demonstrated that the resulting material properties strongly depend upon the selected procedure and its processing conditions. Thus, compression-moulding after blending the ingredients by kneading was seen to produce much more promising results, concerning material transparency and strength, if compared to extrusion. However, results can further be improved by extruding starch and glycerol before blending with the protein.