Carbon black replacement in natural rubber composites using dry-milled calcium carbonate, soy protein, and biochar

Authors: Peterson, Steven - Steve

Submitted to: Processes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2022
Publication Date: 1/7/2022
Citation: Peterson, S.C. 2022. Carbon black replacement in natural rubber composites using dry-milled calcium carbonate, soy protein, and biochar. Processes. 10(1). Article 123. https://doi.org/10.3390/pr10010123.
DOI: https://doi.org/10.3390/pr10010123

Interpretive Summary: Recently it was discovered that calcium carbonate and soy protein could be used to effectively reinforce natural rubber composites, but the method to do this required the soy protein to be microfluidized (reducing the particle size via high pressure in a liquid mixture), mixed with rubber latex, and freeze dried before it was made into a rubber composite. These steps are costly to scale up. In the current work, ARS researchers in Peoria, Illinois, developed a simplified method using dry-milling of calcium carbonate and soy protein combined with biochar from Paulownia hardwood trees. It was found that 40-50% of the carbon black could be replaced with these renewable composite materials from the simplified process with virtually no loss in strength compared to a 100% carbon black-filled control. This method is much more amenable to current rubber manufacturing infrastructure and can reduce carbon black usage, consequently reducing petroleum dependence and improving "green" production of rubber composites.

Technical Abstract: Recent discoveries have shown that calcium carbonate and soy protein interactions can be used to reinforce rubber composites with improvements on the effective crosslink density and moduli. However, the method to incorporate the soy protein into the rubber matrix may be costly to scale up, since it involves microfluidization and drying steps prior to rubber compounding. In this work, a simpler process involving dry-milled calcium carbonate and soy protein was used to explore filler blends of calcium carbonate, soy protein, biochar, and carbon black. By blending these filler materials in various ratios, rubber composite samples with 40–50% of the carbon black replaced by sustainable alternatives were made. These composites had essentially the same tensile strength, with better toughness and elongation properties relative to the carbon black control. These composites would reduce dependence on petroleum and be more amenable to the rubber composite compounding infrastructure.