Hydrated zinc borates and their industrial use

Abstract

Zinc borates are important chemical products having industrial applications as functional additives in polymers, bio-composites, paints and ceramics. Of the thirteen well documented hydrated binary zinc borates, Zn[B3O4(OH)3] (2ZnO•3B2O3•3H2O) is manufactured in the largest quantity and is known as an article of commerce as 2ZnO•3B2O3•3.5H2O. Other hydrated zinc borates in commercial use include 4ZnO•B2O3•H2O, 3ZnO•3B2O3•5H2O and 2ZnO•3B2O3•7H2O. The history, chemistry, and applications of these and other hydrated zinc borate phases are briefly reviewed, and outstanding problems in the field are highlighted.