Effect of Shearing on the Reinforcement Properties of Vital Wheat Gluten

Abstract

An aqueous dispersion of vital wheat gluten and styrenebutadiene rubber was subjected to high-shear mixing in an attempt to reduce the aggregate size and enhance filler—matrix interactions with the goal of improving contributions of the reinforcement to the overall composite properties. Composites were formulated using 10—40% vital wheat gluten by mixing aqueous suspensions of the gluten and rubber, then freeze-drying and compression molding the resulting composite. Rheological experiments indicated that vital wheat gluten reinforced the rubber up to a factor of roughly 30. Subjecting the gluten suspension to high shearing reduced the particle size from approximately 5.2—4.5 µm, and 16 min was the optimum shearing time since shearing the dispersions longer did not result in any additional size reduction. Composites with 10% vital wheat gluten have good potential in applications requiring high elasticity since they were equal to or better than the carbon black control in terms of Young’s modulus, percent elongation, and toughness. Isolated vital wheat gluten was studied in order to determine its relative merit as one of the two reinforcing components of wheat flour (the other being wheat starch), and vital wheat gluten’s reinforcing ability was a factor of 10 weaker than wheat flour, indicating that wheat starch is a much more effective biomaterial filler in terms of rigidity, but vital wheat gluten may be more suitable for applications requiring more elasticity.