Tannic acid as biobased flame retardants: A review

One of the pressing issues in the field of fire safety is the sustainable flame retardancy of polymer materials. Bio-based flame retardants are one of the emerging and promising areas of sustainable flame retardants of the last decade. Tannic acid (TA) is a type of naturally occurring plant polyphenols with a broad source and abundant reserves. In recent years, TA based on textile, steel, and other natural and synthetic polymeric materials has shown great potential for flame retardancy. Depending on the method used and the addition of flame retardants to a flame-retardant system based on TA, various flame retardation modes of action and fire-resistance performances are achieved. This paper reviews the physicochemical properties and thermal properties of TA as well as flame retardancy and fire-retardant mechanism of common polymeric matrixes which are chemically treated by flame retardants (mixture of modified TA and existing flame-retardant additives). Different modes of modification of TA and its roles in flame retardation (e.g., hydrogen bond association, metal ion complexation, carbon source and oxidation resistance) are then worked out in some detail. Achievements in this area have increased our knowledge of the application of TA in the field of flame retardancy and have spurred the development of bio-based flame retardants.