Used primarily as a flame retardant synergist, especially in combination with halogenated compounds. It enhances the fire resistance of plastics, textiles, rubber, and coatings by reducing flammability and slowing the spread of flames. Commonly found in electrical and electronic devices, automotive components, and building materials. Also serves as a catalyst in the production of polyethylene terephthalate (PET) and in the manufacturing of specialty glasses and ceramics.