Coppiced biochars as partial replacement of carbon black filler in polybutadiene/natural rubber composites

Authors: Peterson, Steven - Steve

Submitted to: Journal of Composites Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2020
Publication Date: 9/30/2020
Citation: Peterson, S.C. 2020. Coppiced biochars as partial replacement of carbon black filler in polybutadiene/natural rubber composites. Journal of Composites Science. 4(4):147-157. https://doi.org/10.3390/jcs4040147.
DOI: https://doi.org/10.3390/jcs4040147

Interpretive Summary: Carbon black is made from natural gas and is often used to reinforce rubber. One of the advantages of carbon black is its very small particle size (larger particles initiate failure points in the rubber). Up to 40% of a rubber car tire can be carbon black and replacing it with a biobased renewable material would make tire production much greener. In this research, 30% of the total amount of carbon black in a rubber composite was replaced with biochar made from renewable Paulownia and poplar hardwood trees with no loss of strength and improved elongation and toughness properties. This is important because sustainable, renewable sources of carbon need to be developed to reduce our dependence on fossil fuels. Biochars were made from two hardwood tree species that are fast-growing, non-competitive with food, and can grow over the majority of North America. These biochars were able to act as drop-in replacements for 30% of the carbon black required to make a rubber composite which is often used in vehicle tires. This research will be important to consumers who care about ecological issues and used by the tire industry. This work will benefit biomass growers and the environment.

Technical Abstract: Although carbon black has been the dominant filler material for rubber composites for over a century, it is a finite, fossil fuel-based product that is sensitive to geopolitical issues and economics. It is imperative that renewable sources of carbon be studied to replace this material in order to reduce dependence on petroleum. Biochar is the solid material left over after the anaerobic treatment of biomass at high temperature. In this work, two biochars made from coppiced hardwoods, Paulownia elongata and Populus tremuloides were used to partially replace carbon black in rubber composites using a 50/50 blend of polybutadiene and natural rubber. Rubber composite samples using these biochars were able to replace 30% of the carbon black with virtually no loss in tensile strength, and improved elongation and toughness compared to the 100% carbon black control.