Boron in Polymers and Coatings


Polymers are part of nearly every area of modern life, from the furniture we use to the packaging of goods we buy to the electronics in our pockets. Our homes include a dizzying array of polymers and composite materials that are used for both interior and exterior construction. From wiring and plumbing fixtures to wall panels, siding, roofing, and decking, polymers provide versatile and durable construction materials.

Polymers can ignite and burn easily which is why flame retardant additives are often required to meet safety standards. One of the many commercial applications of borates is fire retardancy. Among all of the boron-containing fire retardants used in polymers, zinc borate has the most commercial importance. U.S. Borax first patented and commercialized a unique form of zinc borate with a molecular formula of, known in the trade as Firebrake® ZB.

Fire retardant plastics and elastomers

Specialized borate compounds, such as zinc borates, are used as fire retardants and smoke suppressant additives in polymers, plastics, and rubber applications. 

20 Mule Team® Borax Firebrake products, Firebrake 500 and Firebrake ZB, are designed as flame retardants for polymers. Although its applications are extensive and varied, Firebrake ZB, for example, is a multipurpose synergist in both halogen-containing and halogen-free polyolefin. It acts not only as a flame retardant and anti-arcing agent, but as a smoke and after glow suppressor and a promotor of char formation. As a fire-retardant synergist, the product completely or partially replaces antimony oxide in the final product. The applications for boron based fire retardant applications are numerous:

Boron as a flame retardant and anti-arcing agent

  • Wire and cable products
  • Electrical connectors and bobbins
  • Circuit breakers and housings
  • Transformer components
  • Appliance components
  • Wall coverings
  • Foam insulation
  • Mechanical parts
  • Conveyor belts
  • Carpet backing
  • Automotive upholstery
  • Roofing membranes
Char: A hard, intumescent (ie, expanded) residue that some polymers produce during combustion. In effect, part of the polymer is transformed into a solid, carbonaceous mass rather than into smoke or flame. Char reduces the duration of a fire, inhibits its spread, provides electrical insulation to protect wiring even after it is burnt, and prevents short-circuiting and sparking.

Why 20 Mule Team Borax?

Why use 20 Mule Team Borax products instead of antimony oxide or competing borates for fire suppression in insulations and polymer products and production?
  • Less product caking
  • Consistent and reliable quality: Customers can use our certificate of authenticity (COA) data in batch formulation, eliminating the need for onsite QA/QC and improving the production process
  • Decades of research and expertise: Exclusive, extensive knowledge regarding boron volatility, borate chemical and physical analysis and troubleshooting, and global regulations

20 Mule Team Borax Products

These 20 Mule Team Borax products are developed for polymer use.

Ammonium Pentaborate

Whether inhibiting heat, flame, or corrosion, the purity of this alkaline salt makes it an excellent choice. Learn More

Borax Decahydrate

From detergents to dyes to adhesives, this mild alkaline salt does it all, particularly excelling as a buffering and fluxing agent. Learn More

Boric Oxide

Pure anhydrous form is ideal where boric acid is required without metals. A powerful tool in the production of specialty glasses, ceramics, enamels, and fluxes. Learn More


These products are unique zinc borates combining the best of zinc and boron oxides that can be used to develop fire-retardant formulations. Learn More

Firebrake 500

This zinc borate is anhydrous—it contains no water of hydration—which makes it highly stable in fire-retardant applications and in polymer systems that require very high processing temperatures. Learn More

Firebrake ZB

This unique zinc borate combines the best of zinc and boron oxides with water release to provide multi-functional benefits in fire-retardant formulations. Learn More


With lower transportation, handling, and storage costs, this concentrated sodium borate is used in glass, fiberglass, cleaning products, and flame retardants. Learn More

Optibor boric acid

From reducing melting temperatures in fiberglass production to inhibiting corrosion in fuel additives, Optibor has a multitude of uses in numerous industries. Learn More


Polybor earns its spot in industrial cleaning compounds, fire retardants, and the manufacture of water-treatment chemicals. Learn More

More About Borates in Polymers and Coatings

Meet the Maestro of Polymer Fire Retardancy
U.S. Borax celebrates the exceptional career of Kelvin Shen. For 50 years, Kelvin has been the go-to expert for polymer manufacturers looking for the right fi... Learn More
Borates in Automobiles
Look closely, and you’ll find a wide range of applications of borates in automobiles. In fact, auto makers find uses for borates in nearly every part an... Learn More
Zinc Borates for Fire Retardancy, Safety, and Performance
Polymer producers face a range of challenges as they strive to find a balance of safety, sustainability, and quality in their products. Firebrake produ... Learn More

U.S. Borax, part of Rio Tinto, is a global leader in the supply and science of borates—naturally-occurring minerals containing boron and other elements. We are 1,000 people serving 500 customers with more than 1,700 delivery locations globally. We supply 30% of the world’s need for refined borates from our world-class mine in Boron, California, about 100 miles northeast of Los Angeles.  Learn more about Rio Tinto.

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