Firebrake 500


Polymer protection for high processing temperatures

As a dehydrated zinc borate, Firebrake® 500 has numerous applications as a fire retardant and can be fed into extruders, calendars, and injection molding equipment.
Firebrake fire protection

Stable Up to  600°C

Firebrake 500 is a dehydrated zinc borate for multi-functional fire retardant applications in a variety of polymers. Because it contains no water of hydration, it is stable up to 1112°F (600°C) and can be used in polymer systems that require very high processing temperatures. The product can be fed to extruders, calendars, or injection molding equipment in the same way as other solid polymer additives.


Firebrake 500 is an anhydrous form of Firebrake ZB that is specially designed for applications in which no water evolution is permitted. The product provides the performance associated with the optimal combination of zinc and boron found in Firebrake ZB. You can use Firebrake 500 as a flame retardant, char promoter, and smoke suppressant in a variety of polymers, including:
  • Nylons
  • Polyetherketones
  • Polysulfones
  • Fluoropolymers
  • Polyesters
Firebrake 500 has a significant beneficial effect on the rate of heat release, a quality that is of special interest in aircraft applications.
Stable up to 600°C, Firebrake 500 can be used in polymer systems with high processing temperatures.



Firebrake 500 has numerous fire retardant applications and can be fed into extruders, calendars, and injection molding equipment.


Store Firebrake 500 in a sealed container because of its tendency to gradually pick up surface moisture in high-humidity environments. This surface moisture is easily removed by heating at about 200°C.

Chemical and Physical Properties

Refractive Index: 1.58

Median Particle Size: ≤12 microns (laser diffraction)

Weight Loss (TGA): 1.5% maximum to 400°C

Stability:  Thermally stable to >600°C; can gradually absorb surface moisture

Molecular weight: 371.62

Specific gravity: 2.6

Appearance: White, crystal like powder

Stability: The product is chemically stable and shows little tendency to cake.

Chemical Composition (Theoretical)

Boric oxide, B2O3: 56.20%

Zinc oxide, ZnO: 43.80%

Containers: Products may be available in bulk, IBCs, or small bags.

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 east of Los Angeles.  Learn more about Rio Tinto

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