Reducing biochar particle size with nanosilica and its effect on rubber composite reinforcement

Authors: Peterson, Steven - Steve; Kim, Sanghoon

Submitted to: Journal of Polymers and the Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2019
Publication Date: 11/19/2019
Citation: Peterson, S.C., Kim, S. 2020. Reducing biochar particle size with nanosilica and its effect on rubber composite reinforcement. Journal of Polymers and the Environment. 28:317-322. https://doi.org/10.1007/s10924-019-01604-x.
DOI: https://doi.org/10.1007/s10924-019-01604-x

Interpretive Summary: Biochar is a renewable source of carbon that has been researched as a potential carbon black substitute in rubber composites. In this research we demonstrated a new technique of milling a small amount of silica nanoparticles with biochar in order to reduce the size of the biochar particles. This increases their surface area and makes them much more effective at strengthening rubber composites. An added bonus of this technique is that the silica does not need to be removed from the mixture since it is an effective rubber composite filler as well, so this makes the process more attractive to industry. It was found that by co-milling biochar with only 1% (by weight) nanosilica, 40% of the carbon black could be replaced by biochar in a rubber composite with virtually no loss in tensile strength, and improvements in both elongation and toughness of 31% and 24%, respectively, compared to a 100% carbon black control.

Technical Abstract: Since biochar is a renewable source of carbon, it has been examined as a substitute for carbon black as rubber composite filler. Although biochar can approach carbon black in terms of carbon and ash content, substituting carbon black with biochar typically degrades the mechanical properties of rubber composites because of the much larger particle size of biochar. Biochar is produced from biomass and must be size reduced by "top-down" methods such as milling. Thus, biochar frequently has populations of particles greater than 10 microns in diameter, which greatly reduce reinforcement properties by introducing localized stresses in the rubber composite. In this work we explore using nanosilica as a co-milling material with biochar as a means to reduce its particle size and consequently improve its ability to replace carbon black as rubber composite filler. Biochar co-milled with 1 wt% nanosilica was able to replace 40% of the carbon black filler in a styrene-butadiene rubber composite with virtually no loss in tensile strength. Also, elongation and toughness properties of the optimal biochar substituted composites were improved by over 31 and 24%, respectively.