Amspec KR is a grade of antimony trioxide appropriate for use as a flame retardant synergist used in combination with a halogen compound. Many materials utilize its flame retardant properties including plastics, rubber, paints, paper, textiles and electronics. Antimony trioxide is appropriate for use in polypropylene (PP), polyethylene (PE), ethylene propylene diene M-class rubber (EPDM), polyvinyl chloride (PVC), high impact polystyrene (HIPS), acrylonitrile butadiene styrene (ABS), polyurethanes, phenolics, epoxies, and many others.

Other applications of antimony trioxide include a clarifying agent for glass, an opacifier for porcelain and enamel, and a white pigment.