Borates Are the Multi-Tool for Fire Safety in Plastics and Polymers

:: Tuesday, May 21, 2019 :: Posted By Maryam Moravej
Polymers and plastics play big roles in modern construction. Plastics and polymers in construction are used throughout our homes and offices, from basement to roof, offering a diverse range of solutions to modern construction challenges.

Like these versatile materials, borates are also multifunctional, offering a variety of benefits that make them the flame retardant of choice for increasing fire safety in plastics and polymers—and helping manufacturers keep costs in check.

Promoting fire safety in polymers, plastics

Building codes, such as the International Building Code (IBC) and International Residential Code (IRC), regulate polymers and plastics in construction—including requirements related to fire safety. Traditionally, plastics manufacturers have used antimony oxide (or other high-cost flame retardants) as a synergist to enhance the fire retardancy of halogen-containing polymers.

However, as manufacturers look for continuous improvement in the performance of their products—and continuous reduction in the cost of producing them—they have sought cost-effective alternatives for improving smoke suppression and fire retardancy in many of the polymers, plastics, and rubbers that are found in modern homes and offices:
  • Foam insulation
  • Roofing membranes
  • Skylights
  • Interior finish and trim
  • Caulks, sealants, and epoxy resins
  • Wiring and cables
  • Electrical connectors and bobbins
  • Circuit breakers and housings
  • Fabric and upholstery
  • Carpet backing
  • Wall coverings
  • Light covers and wall panels
  • Epoxy

Borates, alone or in combination with other substances, provide an improved solution. One of the best substitutes for antimony oxide is zinc borate, which answers manufacturers’ needs for better performance and improved cost. In contrast to antimony oxide, zinc borate is a smoke suppressant in halogen-containing polymers.

In addition to being an economical additive, 20 Mule Team® Borax Firebrake® products have attributes that help manufacturers manage their overall production costs. For example, they have a refractive index that is similar to most polymer systems. That means that when they are added to the polymer formulation, they help retain translucency, enabling low pigment loading while maintaining true color.
The products are also ideal in high processing temperatures required for many modern applications. Firebrake ZB is recommended for temperatures as high as 554°F (290°C). Firebrake 500—an anhydrous form of Firebrake ZB that is stable up to 1112°F (600°C)—is designed for applications that don’t permit water evolution.

How do borates improve fire safety? Let’s count the ways

Borates like those in Firebrake and ammonium pentaborate products provide increased value to manufacturers because they improve fire safety in multiple ways. They display synergistic effects with halogen or a variety of halogen-free systems, such as metal hydroxides, nitrogen and phosphorus compounds, and silicon-based flame retardants.

Borates produce three significant effects that help enhance fire safety in plastics and polymers

Flame retardancy

Firebrake products and ammonium pentaborate work to protect polymers, plastics, and rubbers across a wide spectrum. The products can often be used interchangeably, but each provides specific benefits as well. For example, Firebrake ZB combines the benefits of zinc and boron and can be used with silica, ammonium polyphosphate, or expandable graphite in halogen-free silicone elastomers and thermo-plastic urethanes.

Smoke and afterglow suppression

Firebrake products suppress smoke and retard fire in a multitude of materials used throughout homes and offices, including:
  • Polyetherketone: PEEK—used in electrical cable insulation
  • Polysulfone: PSU—found in electronics, appliances, and plumbing as well as automobile components
  • Fluoropolymer: used in a variety of fabrics and cookware
  • Polyester nylon

Char promotion

Borates promote the formation of char, which helps to reduce the spread and duration of fire and helps to protect wiring and prevent short-circuiting and sparking.
Ammonium pentaborate promotes char formation in epoxies, urethane foam, and thermoplastic polyurethane (TPU—a common adhesive and textile coating). By inhibiting oxidation, ammonium pentaborate solutions can work alone or as part of other formulations.

Firebrake for fire retardancy across industries and applications

The multifunctional nature of fire retardant effects in Firebrake products makes them highly useful in a variety of polymer and plastics applications.

Sealants: Flooring, trim, cables, piping

Firebrake products can be used in sealants to help prevent the spread of fire by providing intumescence. That means that when the sealant is heated in the type of temperatures produced by a fire, it expands into openings between doors, cables, and pipes.

Epoxy: Flooring, trim

Firebrake helps to retard flame and suppress smoke and afterglow in epoxy adhesives—both those that contain halogen and those that do not. Both Firebrake products can replace a portion or all of the antimony trioxide in halogen-containing formulations; Firebrake ZB can suppress smoke formation even when antimony oxide is present. The product displays synergy when used with ammonium polyphosphate, alumina trihydrate, or silica in halogen-free epoxies. 

Polyvinyls and polyesters: Wiring and cables, piping, flooring, roofing, trim

Firebrake helps to protect wires, cables, flooring, roofing membrane, and foamed insulation made from polyvinyl chloride, nylon, epoxy, polyethylene, polypropylene, polyesters, thermoplastic elastomers, and rubbers.

Other plastics: Insulation, carpet, roofing

Firebrake has multifunctional fire-retardant applications in plastic and rubber compounds. For maximum fire-test performance and for film forming and adhesion, the products are available in fine and extra-fine formulations as well as in standard grade. The extra-fine grade has no particles greater than 12 microns (as determined by laser diffraction) and is suitable for more critical flame-retardant applications.

Cost-effective construction

Using materials that meet fire safety standards—not to mention impart benefits such as energy efficiency or resistance to fluctuations in temperature and humidity—is a smart move for builders. Effective products, proven performance, a reliable supply chain, and outstanding customer service all provide value and improve ROI.
Want to learn more? Our experts are available to answer questions and help you find the right borate formulations.



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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