Submitted to: Composites Part A Applied Science and Manufacturing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 16, 2005
Publication Date: March 1, 2006
Citation: Jong, L. 2006. Effect of soy protein concentrate in elastomer composites. Composites Part A Applied Science and Manufacturing. 37(3):438-446. Interpretive Summary: In rubber composite applications, most rubber products are filled with reinforcement materials. From the perspective of renewal materials and environmental reasons, it is desirable to use natural materials that have the same or better functions. Previously, we have used soy protein isolate to increase significantly the strength of rubber composites. In a continuous effort to find new industrial applications for soy products, the structure and function of soy protein concentrate in a rubber composite are characterized to give a better understanding of its utility. Reinforcement mechanism of soy protein concentrate in rubber using carboxylated poly(styrene-butadiene) as composite matrix is characterized by dynamic mechanical method. The result indicates soy protein concentrate is a more cost effective option than soy protein isolate in terms of the composite properties and cost. This development will be of general interest to technologists developing new rubber products and will be beneficial to soybean farmers by creating new markets for soybean products.
Technical Abstract: Soy protein concentrate (SPC) is an abundant renewable material and is more economically favorable then soy protein isolate. SPC contains both soy protein and soy carbohydrate. The aqueous dispersion of SPC is blended with styrene-butadiene latex to form elastomer composites. The inclusion of soy carbohydrate in the soy protein increases the shear elastic modulus in the small strain region as well as improves the recovery behavior in the non-linear region. At small strain, the equilibrium elastic modulus of 30% filled composites at 140 deg C is about 600 times higher than that of the unfilled elastomer, indicating a significant reinforcement effect generated by SPC. Compared with soy protein isolate, the stress softening effect and recovery behavior under dynamic strain indicate the addition of soy carbohydrate may have increased the filler-rubber interaction. The use of SPC in the rubber reinforcement appears to be a more favorable option than soy protein isolate in terms of both economy and performance.