| Abstract: | Soy spent flakes (SSF) is a plentiful renewable material from the waste stream of commercial soy protein extraction. SSF contains mostly soy carbohydrate and a small fraction of soy protein. Dry SSF is a rigid material and has a shear elastic modulus of ～4 GPa. Aqueous dispersions of SSF were blended with styrene‐butadiene (SB) latex to form rubber composites. Soy carbohydrate increased the tensile stress in the small strain region, but also decreased the elongation at break. The shear elastic modulus of the composites showed an increase in the small strain region, consistent with the stress–strain behavior. The SSF composites showed a slightly better modulus recovery than the protein composite after eight cycles of strain sweep. In the small strain region, the shear elastic modulus of 30 % filled composites at 140 °C was about 160 times greater than that of the unfilled elastomer, showing a significant reinforcement effect caused by SSF. Compared with soy protein isolate, the recovery behavior after eight cycles of dynamic strain suggests that SSF composites have a slightly stronger filler–rubber interaction. In general, SSF composites gave a slightly higher composite strength compared with the protein composites, but at a much lower cost. Published in 2005 by John Wiley & Sons, Ltd. |
