Biocomposites Developed Using Protein-Based Materials as Matrix
Unlike the familiar approach of using natural fibers or agricultural residues as reinforcement and synthetic polymers as matrix, attempts have been made to use matrix from renewable resources with various types of reinforcement [13Mon]. In one such attempt, wheat gluten was used as the matrix and wheat straw ground to various lengths was used as reinforcement. Wheat straw lengths obtained were 2 mm, 0.2 mm, and less than 0.2 μm. The ground wheat straw was mixed with wheat gluten with the addition of glycerol (30 %) as plasticizer, and the mixture was compression molded at 120 °C for 5 min. Some of the properties of the composites obtained are given in Table 69.1. As seen from the table, increasing the fiber content increased the strength and modulus but decreased the elongation. Similarly, impact- and ball-milled fibers provided better tensile properties than the cut-milled fibers at similar levels of fiber loading [13Mon]. Although composites made using wheat gluten and wheat straws have good tensile properties, the wheat gluten and plasticizer are highly hydrophilic and absorb considerable amounts of water. Such composites are expected to have poor stability at high humidities or under aqueous environments and therefore not useful for practical applications.