Synergistic Effect of Calcium Carbonate and Biobased Particles for Rubber Reinforcement and Comparison to Silica Reinforced Rubber

Abstract

Silica is a standard commercial filler to reduce rolling resistance of tires. The co-filler of nano-size calcium carbonate and bio-based particles also produce reinforced rubber with similar tensile properties and rolling resistance as silica reinforced rubber. A synergistic effect between calcium carbonate and soy protein nanoparticles was observed to produce reinforced rubber with good tensile properties and low rolling resistance. The protein increases the effective crosslink density and moduli of calcium carbonate reinforced rubber. Stearic acid coated calcium carbonate particles have a greater reinforcement effect than the uncoated calcium carbonate particles. Mechanical properties of the composites can be adjusted through the complimentary effect of these two fillers. The composite that contains 60% protein and 40% coated calcium carbonate has mechanical properties comparable to that of the silica reinforced rubber. The temperature and strain dependent dynamic mechanical properties, as well as the stress relaxation behaviors of these rubbers, reveal synergistic effect between the co-fillers. This development demonstrates an economical method to produce useful reinforced rubbers.