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 promoting char formation and reducing flammable gas release during combustion. Commonly found in electrical appliances, construction materials, and automotive components where fire safety is critical. Also serves as a catalyst in the production of polyethylene terephthalate (PET) plastic and in certain glass and ceramic applications for improving clarity and stability.