Boron in Glass and Textile Fiberglass


It’s clear: Glass is a vital component of modern living. You’re likely surrounded by it right now. Mobile device screens, windows, bottles and jars for food and drink, lightbulbs, solar arrays, drinking glasses, cosmetics jars, microwave dishes, test tubes and beakers, coffee pots … the list goes on and on.

Many of these items are formed of borosilicate glass, made with silica and 5-20% boric oxide—specifically, boron trioxide. Borosilicate glass is valued for its resistance to heat, chemicals, shocks, and scratches. Its strength and formability make it an important component of products like Pyrex cookware, laboratory glassware, lighting, solar arrays, and domestic appliances.

Boron is also a vital component in the manufacture of textile fiberglass (also known as continuous strand fiberglass, or simply fiberglass). Produced in a variety of fiber types and forms, the majority of textile fiberglass is used in wind turbine blades and vehicles.

Applications of borosilicate glass and textile fiberglass are plentiful:

  • Display screens in cell phones, tablets, and TVs
  • Ovenware, tableware, and microwave dishes
  • Laboratory glass
  • Pharmaceutical and cosmetics packaging
  • Lighting glass
  • Glass microspheres
  • Boats, cars, trucks, trains, and aircraft

  • Wind turbine blades
  • Printed circuit boards (PCBs)
  • Aerospace applications
  • Fiberglass pipes and tanks
  • Glass beads
  • Glass-to-metal sealing, such as in radio valves
Boric oxide is used in the preparation of boron halides, sodium borohydride, metallic borates, and borate esters and as a catalyst in the conversion and synthesis of many organic compounds

Boric oxide in glass manufacturing

In the glass and textile fiberglass manufacturing process, boric oxide functions as both a flux and network former. It significantly lowers melting temperature and inhibits crystallization of the glass, both of which greatly facilitate processing. Generally, boric oxide lowers viscosity, controls thermal expansion, and inhibits devitrification—increasing durability and chemical resistance and reducing susceptibility to mechanical or thermal shock.

Borates can also positively affect the properties of the final product. For example, borates act as a powerful flux and lower glass batch melting temperatures during fiberglass manufacturing, aiding the fiberizing process and improving durability in use. And when those glass fibers are used in electronics or aerospace applications, borates enable control of dielectric properties—one reason textile fiberglass made with boric oxide is used in the manufacture of printed circuit boards, microelectromechanical systems, and thermal insulation tiles like those on the U.S. space shuttle.

Textile fiberglass

Textile fiberglass comes in several types (A, C, E-CR, D, E, R, or S) and forms (rovings, yarns, chopped strands, milled fibers, or woven and mat textiles). Most (90-95%) textile fiberglass products are E-glass (aka electronic glass). Originally aimed at electrical applications, E-glass is now primarily used to reinforce thermoset and thermoplastic polymer composite structures, known as fiber reinforced plastic (FRP) or glass fiber reinforced plastic (GFRP).

In the textile industry, E-glass used for printed circuit boards and aerospace applications must contain 5-10% boric oxide (B2O3). E-glass for general reinforcement purposes can vary from 0-10% B2O3. Low-dielectric textile glass fibers, used in high-frequency electronics applications, have a higher B2O3 content than E-glass, reducing the dielectric constant.

With a diameter of a few microns and coated in silane (an inorganic compound) to improve compatibility with matrix material, continuous strand textile glass fibers provide a powerful reinforcement for applications including boats, wind turbine blades, pipes, and lightweight composite structural components in cars, trucks, trains, and aircraft.


Boron for textile fiberglass

Borates for heat resistance and infrared absorption

Borates absorb infrared light and radiation. In domestic solar thermal heating systems, borosilicate glass tubes contain a solar collector that captures solar energy. The industrial version, also known as concentrated solar power, uses large-diameter borosilicate glass tubes that carry a heat-transfer fluid onto which mirrors focus sunlight. Evacuated solar collector tubes for solar water heating rely on the tight control of thermal expansion, the ease of formability, and the durability and impact resistance of borosilicate glass. Some concentrated solar power generation stations in hot countries use large arrays of borosilicate collector tubes to gather reflected radiation from parabolic mirrors for the generation of electricity in steam-driven turbines. These tubes require careful matching of glass and metal thermal expansion and extreme durability in the demanding and remote conditions in which they are installed.


Borosilicate glass tubes

Borates for increased strength and chemical resistance

As a component of borosilicate glass, borates improve resistance to thermal shock, increase aqueous durability and mechanical strength, imbue electrical neutrality, and structurally modify the glass to make it resistant to heat and chemicals. Viewing this page on a tablet or mobile phone? Alkali-free borosilicate glass is used in all thin film transistor liquid crystal display (TFT LCD) substrate glass and some types of scratch-resistant, protective outer layers for touchscreens.

In sealed headlights, lamp covers, halogen bulbs, and fluorescent tubes, borosilicate glass provides high electrical resistance, strength, and durability. Ampoules and vials for medicine, as well as vacuum flasks, rely on borates for increased chemical resistance and aqueous durability. Pharmaceutical (or neutral) glass can be engineered so that, in contact with aqueous solutions, it creates the same pH as is found in the human body. And, borosilicate glass maintains optimum brilliance. Along with its low coefficient of thermal expansion, this makes the material suitable for optics such as astronomical reflecting telescopes and eyeglasses.

Borate-containing glass beads are used in plastics as reinforcement-extenders. Hollow microspheres are used to manufacture automotive parts and patching compounds. Their low-density, high-compressive strength, and insulation from heat and sound make them ideal as light-weight fillers for polymeric materials. Cover glass and substrate glass for flat photovoltaic cells have specific quality and performance requirements that sometimes need to be met by specialized borosilicate glasses, including high strength-to-weight ratio, impact resistance, and surface compatibility with electronics materials.

Boric oxide—specifically pure boron trioxide (B2O3)—is needed for the production of certain types of glasses including optical and telescope lenses, medical glasses (ampoules), electronic glasses, and glass-ceramic composites.

20 Mule Team Borax Products 

These 20 Mule Team Borax products are developed for use in the manufacture of glass and textile fiberglass.

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


This hard, glassy, granular product is excellent when forming flux or glass, where it helps to increase yield and reduce energy consumption. 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


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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 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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