Lei Jong

Reinforcement Effect of Soy Protein/Carbohydrate Ratio in Styrene—Butadiene Polymer:

Soy protein and carbohydrate at different ratios were blended with latex to form composites. The variation of protein-to-carbohydrate ratio has a significant 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.

Effect of Shearing on the Reinforcement Properties of Vital Wheat Gluten

An aqueous dispersion of vital wheat gluten and styrenebutadiene rubber was subjected to high-shear mixing in an attempt to reduce the aggregate size and enhance filler—matrix interactions with the goal of improving contributions of the reinforcement to the overall composite properties. Composites were formulated using 10—40% vital wheat gluten by mixing aqueous suspensions of the gluten and rubber, then freeze-drying and compression molding the resulting composite. Rheological experiments indicated that vital wheat gluten reinforced the rubber up to a factor of roughly 30. Subjecting the gluten suspension to high shearing reduced the particle size from approximately 5.2—4.5 µm, and 16 min was the optimum shearing time since shearing the dispersions longer did not result in any additional size reduction. Composites with 10% vital wheat gluten have good potential in applications requiring high elasticity since they were equal to or better than the carbon black control in terms of Young’s modulus, percent elongation, and toughness. Isolated vital wheat gluten was studied in order to determine its relative merit as one of the two reinforcing components of wheat flour (the other being wheat starch), and vital wheat gluten’s reinforcing ability was a factor of 10 weaker than wheat flour, indicating that wheat starch is a much more effective biomaterial filler in terms of rigidity, but vital wheat gluten may be more suitable for applications requiring more elasticity.

Effect of processing methods on the mechanical properties of natural rubber filled with stearic acid-modified soy protein particles

Natural rubber was reinforced with stearic acid-modified soy protein particles prepared using a microfluidizing and ball milling process. Longer ball milling time tends to increase the tensile strength of the rubber composites. Elastic modulus of the composites increased with the increasing filler concentration. The loss modulus and loss tangent indicated an increase in the amount of polymer immobilized by the modified soy protein. The extent of stearic acid modification affected the mechanical properties of the rubber composites. Compared with the unmodified soy protein, the microfluidized and stearic acid-modified soy protein filler improved the mechanical properties of the rubber composites.

Mechanical properties of heterophase polymer blends of cryogenically fractured soy flour composite filler and poly (styrene-butadiene)

Reinforcement effect of cryogenically fractured soy flour composite filler in soft polymer was investigated in this study. Polymer composites were prepared by melt-mixing polymer and soy flour composite fillers in an internal mixer. Soy flour composite fillers were prepared by blending aqueous soy flour dispersion and styrene–butadiene rubber latex to form a mixture, which was then dried and cryogenically ground into powders. Upon cross-linking, the heterophase composite filler was integrated into rubber polymer and exhibited enhanced mechanical properties. Tensile strength, elongation, Young’s modulus, toughness, and tear resistance of the heterophase polymer composites were better than those of the polymer matrix. The composites reinforced by the composite fillers prepared with different polymer matrices showed that the composite filler prepared with styrene–butadiene instead of carboxylated styrene–butadiene matrix produced composites with greater elongation ratio and toughness but smaller Young’s modulus. The study of elongation rate showed that the soy flour composite fillers produced the composites with useful tensile strength, elongation ratio, and toughness at 500 mm/min strain rate. The study also showed that the effect of soy flour/polymer ratio of the composite fillers on the composite mechanical properties was small.