*Article* **Lauric Acid Treatments to Oxidized and Control Biochars and Their Effects on Rubber Composite Tensile Properties**

**Steven C. Peterson \* and A. J. Thomas**

USDA, Agricultural Research Service, National Center for Agricultural Utilization Research, Plant Polymer Research, 1815 N University, Peoria, IL 61604, USA

**\*** Correspondence: steve.peterson@usda.gov

**Abstract:** Biochar is a renewable source of carbon that can partially replace carbon black as filler in rubber composites. Since the carbon content of biochar is less pure than carbon black, improvements and modifications must be made to biochar to make it a viable co-filler. In this work, two methods to change the surface chemistry of biochar were employed: (1) gas treatment at 300 ◦C with either air or carbon dioxide, and (2) coating with lauric acid. Both methods are amenable to the current rubber processing industry. After biochar was treated with these methods, it was used as co-filler in rubber composite samples. Gas treatment with either air or carbon dioxide was found to increase stiffness in the final composites. Although lauric acid coating of biochar by itself did not have a significant effect on tensile properties, biochar that was first treated with carbon dioxide and then coated with lauric acid showed a 19% increase in tensile strength and a 48% increase in toughness. Gas treatment and lauric acid coating of biochar provide relatively simple processing techniques to improve the stiffness and tensile strength of biochar as rubber composite filler.

**Keywords:** biochar; surface treatment; lauric acid; rubber composite

**Citation:** Peterson, S.C.; Thomas, A.J. Lauric Acid Treatments to Oxidized and Control Biochars and Their Effects on Rubber Composite Tensile Properties. *C* **2022**, *8*, 58. https:// doi.org/10.3390/c8040058

Academic Editors: Indra Pulidindi, Pankaj Sharma and Aharon Gedanken

Received: 29 September 2022 Accepted: 27 October 2022 Published: 29 October 2022

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