Boron in Polymers


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:

  • 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


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

More About Borates in Polymers 

Firebrake 500 for Polymers: Multiple Benefits for High-Temperature Processes
Firebrake 500 is an anhydrous zinc borate that’s designed to stand up to high-temperature polymer processes. Polymer manufactures gain multiple b... Learn More
Firebrake ZB: A Modern Choice for Fire Retardancy in Polymers
Fire safety is not just about preventing fire, but ensuring that if a fire happens, people can escape it. 20 Mule Team Borax Firebrake ZB is a flame... Learn More
Borates Are the Multi-Tool for Fire Safety in Plastics and Polymers
Borates provide a multifunctional approach to promoting fire retardancy in the polymers and plastics that are prevalent in today’s homes and business co... 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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