Plasticized wheat gluten reinforcement with natural fibers: Effect of thermal treatment on the fiber/matrix adhesion

Wheat gluten-based materials reinforced with hemp fiber were prepared at different thermomolding temperature, and their mechanical properties were characterized. Reinforcement, calculated as the ratio between the composite Young’s modulus and the matrix Young’s modulus was shown to decrease when the thermomolding temperature increased from 100 to 130 °C. However, the feature cannot be explained neither by a matrix deplasticization nor a variation in the extent of gluten cross-linking. The effect of the thermomolding temperature on the pressure sensitive adhesives properties of gluten-based matrix was evaluated by the measurement of their rheological properties (elastic and viscous modulus) at various frequencies. Results confirmed that the better adhesives properties were obtained at lower temperature, suggesting that this parameter affects the reinforcement.