Tannic Acid—A Novel Intumescent Agent for Epoxy Systems

Tannic acid (TA) is a bio-based high molecular weight organic (HMWO), aromatic molecule. Although biologically sourced, TA currently pollutes industrial wastewater streams, and there is an industrial desire to find applications to downcycle this molecule. Epoxy thermosets have revolutionized many industries, but are too flammable to be used in many applications without additives which augment its flame retardancy (FR). Many flame retardants used in epoxy thermosets are synthesized from petroleum-based monomers leading to significant environmental impacts at the industrial scale. Various bio-based modifiers have been developed to improve the FR of the epoxy resin; however, increasing FR of the system without trade-offs with other properties has proven to be challenging. In this work, TA was incorporated into the thermoset. The molecule was found to increase the intumescence of the system without significant changes to the Tg and strength paving the way for biological intumescent agents to be used industrially.