Synergistic effect of calcium carbonate and biobased particles for rubber reinforcement and comparison to silica reinforced rubber

Authors: Jong, Lei

Submitted to: Journal of Composites Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/11/2020
Publication Date: 8/13/2020
Citation: Jong, L. 2020. Synergistic effect of calcium carbonate and biobased particles for rubber reinforcement and comparison to silica reinforced rubber. Journal of Composites Science. 4(3). Article 113. https://doi.org/10.3390/jcs4030113.
DOI: https://doi.org/10.3390/jcs4030113

Interpretive Summary: Commercially, calcium carbonate (calcite) particles have been added to rubbers and plastics to improve strength and reduce cost in the industrial production of tires, wire cables, pipes, and flooring for many decades. However, the strength of rubber reinforced with calcium carbonate is relatively low compared to major fillers such as carbon black and silica. We have increased significantly the strength of calcium carbonate reinforced rubber by partially replacing calcium carbonate particles with soybean derived particles. This accomplishment has increased the potential of using more soybeans in new applications and therefore increases the value of soybean and natural rubber, which will have economic benefit to soybean and natural rubber businesses.

Technical 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.