Phosphite Antioxidant 168

About This Product

Antioxidant 168, tris(2,4-di-tert-butylphenyl) phosphite, CAS 31570-04-4, is a white powder or granule and the most widely used phosphite secondary antioxidant. Its role is different from that of a hindered phenol. A primary antioxidant stops radicals that already exist; a secondary antioxidant removes the hydroperoxides that would otherwise decompose into two new radicals each, cutting off the branching step that makes autoxidation accelerate. The phosphite is oxidised to a phosphate in doing so. Used together, the two classes are markedly more effective than either alone, which is why phenol-phosphite blends are standard in polyolefin stabilisation packages. Phosphite is particularly valuable during melt processing, where it protects colour and melt-flow stability through repeated extrusion. Declared applications are the same polyolefin resins, ABS, polyurethane, polyformaldehyde, synthetic rubber and petroleum products as the phenolic grades.