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.

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.

Oxide is usually sold in powder form in multi-walled paper bags. This is similar to the way halogenated flame-retardants are sold. But, a few select companies will sell liquid dispersions that mix the two together in the appropriate ratios for your material and 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.

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.

Because of its color, white, antimony can also be used as a pigment. One industry that utilizes it this way is the porcelain and enamel industry. Here, the antimony is used as an opacifier in very specific instances. As you can see, the uses of antimony are quite varied and many industries utilize this unique chemical compound.