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.

When you want to flame retard something the most common additives for doing so is a halogenated compound in combination with a synergist. The halogenated compound alone will provide flammability protection, but the presence of the synergist allows you to use much less halogenated product. You can use approximately half as much halogen if you also use an antimony synergist.

The use of antimony as a flame retardant synergist is very widespread. A wide variety of industries use it including plastics, textiles, paint, rubber, and paper. The most common materials that include a halogenated flame retardant and an antimony synergist are polypropylene (PP), high impact polystyrene (HIPS), polyvinyl chloride (PVC), ethylene propylene diene M-class rubber (EPDM), acrylonitrile butadiene styrene (ABS), polyethylene (PE), polyurethanes, epoxies, and phenolics.

Antimony trioxide is typically sold in multi-walled paper bags in powder form. The halogenated product is usually provided in a similar manner. This method of packaging causes a lot of dusting so there is an alternative. Some companies will make a specialized liquid dispersion using whatever medium you desire with the halogenated product and antimony trioxide in whatever ratio suits your process the best.

Polyethylene terephthalate or PET is manufactured using a catalyst and often that catalyst is antimony trioxide. This polymerization process usually requires a more pure grade of antimony than flame retardant applications. Antimony is used more often than other catalysts because of the excellent cost to performance ratio. There are other options that provide better throughput, but they are much more expensive than antimony trioxide.

PET is used to make water bottles and other liquid containers. Because these liquids can sit in the bottle for a long time before consumption, there are some concerns about materials in the PET migrating into the PET. There have been some studies that show antimony will migrate into bottled water, but the concentrations are well below the level where we should be concerned. In addition, the toxicity of antimony is very low and its presence will not likely cause much harm.

Another, less predominant use for antimony trioxide is as a clarifying agent for glass. The clarifying agent is added during the meltdown process and will help to remove any bubbles, inclusions, or unwanted color from the glass. Clarifying agents are what makes glass clear. The natural impurities in sand will make glass light blue or light green if no clarifying agents are added. Antimony trioxide is a good choice because some of the other common clarifying agents will cause the glass to tint. For example, manganese oxide will eventually react with ultraviolet light to turn the glass purple.

Finally, antimony oxide is a white crystalline powder. Because of its color, some small markets use it as a pigment. One such application is as an opacifier for porcelain and enamel. With uses as varied as the ones described here, antimony trioxide is a very useful product.