Borates in Flame Retardants
Boron is used in all dry powder fire extinguishers, as well as in the preparation of fire retardant emulsion paints. It also imparts fire resistance in paper and cellulose insulation. Its use in gypsum board adds not only fire retardant properties and mold resistance, but also aids the manufacturing process by delaying the beginning of set up of gypsum. This enables efficient mixing and homogenizing, a longer pot-life, and improved product quality.
When mixtures of boric acid and borax are used in wood as a preservative, they have imparted the added benefit of slowing the spread of surface flames if burning occurs. This is attributed to their char-formation, low melting point and glassy film formation, which help to block volatile compounds from reaching the flames. Typically, there is a trade-off in borate product selection between controlling the spread of flames versus reducing the extent of smoldering. Compared to other flame retardants, borates often are a preferred choice due to their low cost and the minimal impact on substrate’s physical properties, depending upon the application.