The Many Applications of Antimony Oxide

Antimony trioxide is the main derivative of antimony metal. The metal is mined most often in China, Bolivia, Russia, and South Africa. The oxide derivative can be used in many different industries including the flame retardant industry as a synergist, the plastic manufacturing industry as a catalyst, the glass industry as a clarifying agent, and in porcelain and enamel as an opacifier or white pigment.

A flame retardant synergist is exactly what it sounds like. The synergist works in synergy with a halogenated flame retardant. The synergist allows for the user to add much less flame retardant than they normally would half to do. You can get the same amount of protection from flammability from about half as much halogenated product if you add a small amount of synergist.

The antimony/halogen combination is used to flame retard a great variety of materials. You will find antimony used in the plastics, textiles, rubber, paper, and paint industries. Specific materials that use an antimony synergist include but are not limited to high impact polystyrene (HIPS), polyvinyl chloride (PVC), polypropylene (PP), acrylonitrile butadiene styrene (ABS), polyethylene (PE), propylene diene M-class rubber (EPDM), epoxies, phenolics, and polyurethanes.

Since halogenated compounds are usually sold in multi-walled paper bags then the antimony trioxide is typically sold that way as well. If you use very large quantities then you can also buy the synergist in large tote bags. If you do not want to deal with powders, some specialty flame retardant companies will provide a liquid dispersion with the halogenated compound and antimony trioxide in the appropriate ratios mixed with whatever liquid is appropriate for your process.

The polymerization of polyethylene terephthalate or PET requires a catalyst and one of the best choices for that job is high purity antimony trioxide. This manufacturing practice requires a more pure grade of antimony trioxide than flame-retardants. While there are other catalysts that are more efficient; antimony is still the best choice because of its optimal cost/performance ratio.

The most prevalent use of PET is in the manufacture of water bottles and other liquid containers. Many studies have shown that the toxicity of antimony trioxide is very low, but there are still some concerns about the possible migration of antimony into the liquids held in PET bottles. While the migration does happen, the concentration of antimony present is well below the threshold for concern.

A third use for antimony is as a clarifying agent for glass. A clarifying agent is just what it sounds like; it clears up glass during the manufacturing process. The antimony trioxide is added during the meltdown phase and will help to remove any bubbles or inclusions as well as ensure clear glass as the final product. Sand has natural impurities when left untreated would give you light blue or green glass. Antimony trioxide is a good choice because some other common clarifying agents will give you clear glass to start with, but will degrade with time. For example, manganese dioxide used to be used frequently, but scientists found that over time the manganese reacts with the ultraviolet light from the sun and turns the glass purple.

Antimony trioxide is a white crystalline powder. Because of its color, one last application is as a pigment or opacifier for porcelain and enamel. This is a very small part of the market share for antimony trioxide, but you can see how varied the industries that use antimony can be.