MECHANICAL PROPERTIES AND MOISTURE SENSITIVITY OF VIRGIN AND RECYCLED SOY PROTEIN-CORNSTARCH PLASTICS

摘要

Bio-based materials such as soy protein-cornstarch plastics offer advantages in sustainability compared to fossil fuel-based resins. However, to be competitive with current commodity resins, the mechanical behavior and water resistance of these bio-based materials must be improved. Five formulations of soy protein-cornstarch plastics were compounded and injection molded. The effects of soy protein-to-cornstarch ratio, addition of sodium sulfite, addition of a titanate coupling agent, recycling and ambient relative humidity on tensile properties were evaluated. Material with a soy protein-to-cornstarch ratio of 2:3 showed the best overall tensile properties, with tensile strength of 4.8 MPa, modulus of 154 MPa and elongation at break of 120%. Titanate coupling agent also improved tensile properties. Recycling led to slightly decreased tensile performance. Higher relative humidity led to gel formation and substantial decreases in strength, modulus and elongation.