Submitted to: Proceedings of American Chemical Society National Meeting
Publication Type: Proceedings
Publication Acceptance Date: December 2, 2006
Publication Date: March 25, 2007
Citation: Jong, L., Peterson, S.C. 2007. Effect of ph on the composite modulus of soy protein aggregates and carboxylated styrene-butadiene latex. In: Proceedings of Polymeric Materials: Science and Engineering. American Chemical Society National Meeting, March 25-29, 2007, Chicago, Illinois. 96:476-477. Technical Abstract: Soy protein isolate (SPI) has been reported to have a significant reinforcement effect in styrene-butadiene composites prepared under alkaline condition. SPI is a soy product that remains after soybean oil and soy carbohydrates (both soluble and insoluble) are removed from soybean flakes. SPI is a globular protein and its aggregates are similar to colloidal aggregates. Because SPI is rich in ionic functional groups, it is greatly influenced by the effect of pH, which in turn affects the soy filler-filler and filler-matrix interactions. The effect of pH on the SPI/SB composite modulus is investigated in this study. The results show that the composites prepared at an alkaline pH yield a higher elastic modulus, possibly due to stronger filler-filler and filler-matrix interactions. On the other hand, the moduli of composites prepared at acidic pH are more strongly mediated by the polymer matrix and show a stronger dependence on temperature. For SPI filled composites, the effect of pH on modulus is greater at lower filler concentration. A hydrolyzed and fractionated soy protein isolate (HSPI) was also used to study the pH effect. For HSPI filled composites, the difference between the composite modulus obtained at both alkali and acidic pH is greater than that of SPI filled composites.