Boron in fire retardancy

Mitigate flame risk without compromising quality

When it comes to fire retardant additives, there’s no shortage of options available today. That means you can spend hours testing to find the right formulation—one that’s safe, works with your process, and exceeds flammability requirement standards. A faulty formulation can be costly. It can cause damage to your equipment and may keep your product from reaching the market.

Many materials producers choose boron as a key fire-retardant additive. Why? Because borates possess strong synergistic effects when used with other flame retardants and are effective at enhancing formulation performance. Compared to other additives such as antimony trioxide, borates are a cost-effective, naturally occurring choice.


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How boron-based flame retardants work

Boron-based flame retardants are used in many polymer and cellulosic based products where flammability poses a serious threat.

Borates: The smart choice for fire retardancy

If a fire ignites, borates form a carbonaceous char and provide a protective vitreous layer that strengthens and stabilizes the char. In the case of polymers, this vitreous protective layer acts as an insulator, slows pyrolysis, and creates a barrier to hinder the release of additional gases that can fuel combustion.

  • Inhibit flame combustion

  • Promote char formation

  • Suppress smoke formation and afterglow

  • Are halogen-free

  • Function well with other chemicals

  • Reduce production issues

  • Uphold physical and mechanical properties of products

Above and beyond typical fire protection

For certain products, borates impart benefits that go beyond the traditional scope of fire-retardant additives, including these properties:

  • Anti-tracking

  • Anti-arcing

  • Corrosion resistance

  • UV protection

  • IR absorption

  • Adhesion promotion

Why work with U.S. Borax on your fire-retardant application?

For 150 years, we’ve been a world leader in refined borates. We pioneered the use of zinc borate as a fire retardant with the introduction of our Firebrake® family of products more than 50 years ago.

Purity and consistency—for greatest efficacy

You can expect us to deliver high quality products that meet narrow specifications. We know that even the slightest impurities in flame retardant additives can reduce the product performance and create processing issues. And, because consistency is key in manufacturing processes, we ensure particle size and distribution remains within tight thresholds from batch to batch.

Expertise you can rely on

Our technical team can equip you with the latest knowledge on using borates for fire retardancy and make formulation recommendations that fit your unique processes. We can also help guide you through any regulatory concerns you may have, such as the European Chemical Agency’s Substance of Very High Concern Candidate List.

Polymers and coatings: High thermal stability for problem free processing

Polymers burn and ignite easily. Because they are so susceptible, regulators introduced standards to improve safety and reduce the flammability threat from these materials. Our Firebrake products can help you meet your testing requirements.

Our zinc borates have high thermal stability, making them suitable for water-sensitive polymer processing. Extrusion requires high temperatures to melt and shape polymers. Some fire retardants start decomposing and releasing water below the melting temperature, which can cause defects such as bubbles or blisters. However, Firebrake ZB is stable up to 290°C and won’t lose water until it reaches that point. Our Firebrake 500 product is anhydrous and stable up to 600°C.

Borate-based fire retardant additives for almost every type of polymer system​

  • PVC

  • Polyolefins (polypropylene, polyethylene, EVA)

  • Polyamides (PA6, PA66, PA12)

  • Polystyrene

  • Polyester

  • Epoxy

  • Phenolic

  • Polyurethane

  • Polycarbonate

  • Unsaturated polyester

  • Silicone rubber

  • Neoprene

  • EPDM rubber

  • SBR

  • Coatings (acrylic, epoxy, polyurethane)

  • WPCs (HDPE/PP/PVC with natural fibers)

Learn more about which materials use borates, application methods, and formulation factors to consider. Get the brochure →

Borates for fire retardancy in cellulosic materials

For decades, cellulosic materials manufacturers have applied borate-based fire retardant additives to their products—most notably cellulose insulation. Borates are proven effective at combating these materials’ propensity for combustion.

Borate flame retardants combat the two ways cellulosic materials combust:

  1. Primary mode – where visible flames are present

  2. Secondary mode – where flames are absent (glowing or smoldering)

20 Mule Team Borax Products

Recommended for fire retardancy in polymers and coatings

Firebrake ZB logo

For polymers that demand maximum performance as well as film forming and adhesion, this versatile zinc borate is available in fine and extra-fine grades.

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Firebrake 500 logo

Stable up to 1112°F (600°C), this anhydrous zinc borate can be used in polymer systems that require very high processing temperatures.

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Ammonium pentaborate from U.S. Borax logo

A highly refined borate is Ideal for polymer processes in which alkali metals can’t be used.

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Recommended for fire retardancy in cellulose materials

Optibor logo

Used alone or in combination with other fire-retardancy additives, Optibor yields reliable fire test performance.

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Neobor logo

In combination with U.S. Borax boric acid, this concentrated sodium borate is highly effective at reducing flammability of cellulosic materials.

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Polybor logo

In solution form, this DOT can be applied by spray or dipping for effective treatment of cellulose insulation, cotton batting, paper, and fabric.

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U.S. Borax is a member of:

PINFA North America logo

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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 650 customers with more than 1,800 delivery locations globally. We supply around 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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