The oxidative degradation of polymers as a result of formation of free radicals by heat, UV light or impurities is retarded to a great extent by the use of antioxidants. Polymers that are not stabilized against oxidation degrade, which is manifested by loss of mechanical properties due to decrease of molecular weight, discoloration and brittleness. Hindered phenols and aromatic amines are the so called primary antioxidants which by donation of reactive hydrogen to the peroxy radicals prevent further radical propagation.
Phostacon organophosphites such as triphenylphosphite (TPP) and trisnonylphenylphosphite (TNPP) belong to the group of secondary antioxidants. Their function is to decompose hydroperoxides to non reactive species and in this way to retard the oxidative degradation of polymers. Primary and secondary antioxidants alone, or in combination, maintain the performance integrity of polymers and improve their color and processing stability.