Submitted to: Journal of Applied Polymer Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 4, 2005
Publication Date: May 10, 2005
Citation: Jong, L. 2005. Characterization of defatted soy flour and elastomer composites. Journal of Applied Polymer Science. 98(1):353-361. Interpretive Summary: Defatted soy flour (DSF) is an inexpensive renewable commodity. DSF is a soy product after soybean oil is removed from soybean flakes and is a raw material for the production of soy protein concentrate and isolate. In many rubber related applications, rubber products are filled with reinforcement materials. The focus of the current development is to use a renewable material with the same or better functions than the existing material for rubber reinforcement. Previously, we have used soy protein isolate or soy protein concentrate to increase significantly the strength of rubber composites. The new development is to use low cost DSF in rubber composites, and measure its structure and function for strength enhancement. The reinforcement mechanism of DSF in rubber, using carboxylated poly(styrene-butadiene) as a composite matrix, is characterized by static and dynamic mechanical methods. The results indicate that DSF is a more cost effective option than soy protein isolate or concentrate in terms of both mechanical 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: Defatted soy flour (DSF) is an abundant renewable commodity and is more economically favorable then soy protein isolate or soy protein concentrate. DSF contains soy protein, soy carbohydrate, and soy whey. The aqueous dispersion of DSF was blended with styrene-butadiene latex to form elastomer composites. The inclusion of soy carbohydrate increased the tensile stress in the small strain region, but reduced the elongation at break. The shear elastic modulus of the composites showed an increase in the small strain region, consistent with its stress-strain behavior. The inclusion of soy carbohydrate and soy whey also improved the recovery behavior in the non-linear region. At small strain, the shear elastic modulus of 30% filled composites at 140 deg C was about 500 times higher than that of the unfilled elastomer, indicating a significant reinforcement effect generated by DSF. Compared with soy protein isolate, the stress softening effect and recovery behavior under dynamic strain indicate the addition of soy carbohydrate and soy whey may have increased the filler-rubber interaction. In general, the DSF composites gave better mechanical properties compared with the protein composites.