Submitted to: Journal of Elastomers and Plastics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/10/2010
Publication Date: 3/1/2011
Citation: Jong, L. 2011. Reinforcement effect of soy protein/carbohydrate ratio in styrene-butadiene polymer. Journal of Elastomers and Plastics. 43(1):99-117. Interpretive Summary: When soy products (including soy protein isolate, defatted soy flour, soy protein concentrate, and soy spent flakes) were incorporated into polymer composites, they showed substantial reinforcement effects. These soy products have a different protein/carbohydrate ratio and were observed to have different reinforcement effects. To further the development, soy protein isolate and soy carbohydrate were combined at different ratios as co-fillers and their effects on the mechanical properties of the composites were measured. The conclusion is that soy co-fillers with a higher protein/carbohydrate ratio have potential to be used as rubber reinforcement. This development will be of general interest for practical applications to technologists developing new rubber products and will be beneficial to soybean farmers by creating new markets for soy products.
Technical Abstract: Soy protein and carbohydrate at different ratios were blended with latex to form composites. The variation of protein to carbohydrate ratio has a sifnificant effect on the composite properties and the results from dynamic mechanical method showed a substantial reinforcement effect. The composites reinforced by the filler with higher protein content had higher moduli than the composites with higher carbohydrate content. Soy carbohydrate also appeared to have ability to immobilize polymer chains compared to soy protein. The fatigue experiments showed that the composites with higher protein content were more elastic than the composites with higher carbohydrate content after repeatedly stressed with dynamic strain cycles. The recovery experiments showed that the moduli of the composites with higher protein content had better long-time recovery after deformation. The analysis of equilibrated residual structure after the stress softening cycles showed that the composites with higher protein content were resilient without yielding until a larger strain was applied, while the composites with higher carbohydrate content had a continuous yielding in their structures as the magnitude of the strain was increased. Overall, the study shows that soy fillers with higher protein/carbohydrate ratio have potential to be used as rubber reinforcement.