Torrefied agro-industrial residue as filler in natural rubber compounds

Authors: Torres, Lennard; McCaffrey, Zachariah - Zach; WASHINGTON, WISDOM - Volunteer; Williams, Tina; Wood, Delilah - De; Orts, William; McMahan, Colleen

Submitted to: Journal of Applied Polymer Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2021
Publication Date: 3/11/2021
Citation: Torres, L.F., McCaffrey, Z., Washington, W., Williams, T.G., Wood, D.F., Orts, W.J., McMahan, C.M. 2021. Torrefied agro-industrial residue as filler in natural rubber compounds. Journal of Applied Polymer Science. 138(28). Article e50684. https://doi.org/10.1002/app.50684.
DOI: https://doi.org/10.1002/app.50684

Interpretive Summary: In addition to food production, the agricultural industry produces massive quantities of biomass residues, such as almond shells and twigs, rice hulls and rice straw to name a few. Some of the biomass may be used as animal bedding, cattle feed or as roadside erosion control. However, the supply of biomass is outpacing the demand. Alternative, value-added uses of biomass is needed to supplement farmer income, lower disposal costs and reduce landfill space. Biomass may be used as fillers and as replacements for petroleum-derived products thereby reducing greenhouse gas emissions. In this study, we heat-treated almond shells and rice hulls and compared the properties of the heat-treated biomass as replacements or partial replacement of petroleum-derived carbon black in rubber compounds. Results are promising and show that the heat-treated biomass products have comparable characteristics to carbon black as an additive.

Technical Abstract: This study explored the feasibility of using torrefied biomass as a reinforcing filler in natural rubber compounds. Carbon black was then replaced with the torrefied biomass in elastomer formulations for concentration varying from 0 to 100 percent (60 phr total). Their influence on the curing process, dynamic properties, and mechanical properties was investigated. Results were compared with the properties of vulcanizates containing solely carbon black fillers. Time to cure (t90) for compounds with torrefied biomass fillers increased, while filler-filler interactions ( delta G’) decreased, compared to carbon black controls. At low strains, the tan d values of the torrefied fillers vulcanizates were similar to the controls. Incorporation of torrefied biomass into natural rubber decreased compound tensile strength and modulus but increased elongation. Replacement with torrefied fillers resulted in a weaker filler network in the matrix. Still, results showed that moderate substitution concentrations (~20 phr) could be feasible for some natural rubber applications.