Antioxidant Agents

Oxidation inhibitors or also antioxygenes are organic compounds of different compositions which slow down the oxidative degradation of polymers by intervening into the radical chain reaction of the oxidative degradation. One has to differ between primary antioxidants which protect the plastic in the final application and secondary antioxidants which are needed during the processing of plastics. To the first group, also called long-term heat stabilizers, also belong sterically hindered phenols, hydroquinones, organic sulphides, polysulphides, dithiocarbamate, pyrocatechine, aromatic amines as well as their metal complexes. The second group contains phosphites and phosphonates which work as processing stabilizers. Antioxidants use to be radical interceptors which oppose the free radicals during autoxidation. These extract e.g. the atom of the hydroxy group out of the hydroquinones, so that these b

ecome semiquinone radicals. By disproportioning the 2 semiquinone radicals are formed back to 1 quinone and 1 hydroquinone. The original radical is stabilized by the absorption of the H-atom, so that the chain reaction of the oxidation is stopped. The kind and quantity of these additives in our masterbatches depend on the polymer type and its processing conditions as well as on the requirements in the final application.

Ageing

Due to irreversible chemical and physical processes the characteristic material properties such as toughness, transparency, color etc. deteriorate. The most frequent causes are heat, light, energetic radiation, chemicals, weather, ozone or combinations of these parameters.

Ageing Inhibitors

are stabilizers which slow down or inhibit the damaging influence of oxygene, ozone, light, temperature, humidity or heavy metals on plastics. Depending on their function these additives are classified in antioxidants, antiozoniants, light stabilizers which often are effective as radical interceptors.