Review on application of tannins in dyeing and coating

Tannins are natural biocompatible compounds and are abundantly available in plant sources. Tannins have a polyphenolic structure similar to chemical phenols. Various methods have been reported for the extraction of tannins, and the solid-liquid method with the use of water as a solvent is very common. Tannins also have antioxidant properties, and their health and medical applications are related to this property. The common uses of tannins are leather tanning, livestock and fishery feed, beverage production and wood glue preparation. Nowadays, due to the structure of polyphenol tannins and attention to environmental issues, studies are being conducted to develop its applications. Some of the emerging applications of tannins are corrosion inhibitors, improving the properties of dyed fibers, wood protective coatings, preparation of polyurethane resins, etc. This article introduces tannin, extraction methods, and the most important uses of tannins, as well as the latest published research. In the end, cost and commercialization limitations are examined.