Submitted to: Journal of Applied Polymer Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 25, 2010
Publication Date: February 15, 2011
Citation: Jong, L. 2011. Aggregate structure and effect of phthalic anhydride modified soy protein on the mechanical properties of styrene-butadiene copolymer. Journal of Applied Polymer Science. 119(4):1992-2001. Interpretive Summary: Our previous developments showed that soy protein isolate as filler increased the strength of rubber composites significantly. In the current development, phtalic anhydride modified soy protein was found to significantly increase the strength of rubber composites and the composites prepared at acidic pH was found to have recovery properties similar to that of carbon black. This development will be of general interest and practical applications to technologists developing new rubber products and will be beneficial to soybean farmers by creating new markets for soy products.
Technical Abstract: The aggregate structure of phthalic anhydride (PA) modified soy protein isolate (SPI) was investigated by estimating its fractal dimension from the equilibrated dynamic strain sweep experiments. The estimated fractal dimensions of the filler aggregates were less than 2, indicating that these particle aggregates have a distorted or broken two-dimensional sheet-like structure. The results also indicated that the aggregate structure has a greater effect on the composite reinforcement than the overall aggregate size. Tensile strength, elongation,Young's modulus, and toughness of hydrolyzed/modified soy composites are comparable to those of carbon black reinforced composites at 10-15% filler fraction. The moduli of PA-modified SPI composites were less sensitive to the pH of the composite preparation compared to the unmodified SPI. The composites prepared at acidic pH, with lower filler fraction, or filled with hydrolyzed/modified SPI are more elastic and less fatigue. The composites of PA-modified SPI had better recovery properties when prepared at acidic instead of alkali pH. PA-modified hydrolyzed SPI composites prepared at acidic pH showed a similar recovery property to that of carbon black reinforced composites, but with greater shear elastic moduli.