Antioxidants are compounds that inhibit oxidation (usually occurring as autoxidation), a chemical reaction that can produce free radicals. This product polymers from oxidation by controlling changes in molecular weight that lead to loss of physical, mechanical, and optical properties. These types include phenolic antioxidants (AO), primary antioxidants, phosphate antioxidants, thioester antioxidants, amino acid antioxidants, and binary blends, which combine primary (phenolic) antioxidants with secondary (phosphate) antioxidants for optimal stabilization and are available in various forms depending on customer requirements.