Protective Measures Against Aging Processes

Suitable antioxidants (stabilizers) are used to protect plastics against the effects of air oxygen, heat, and sunlight. The stabilizers exert an inhibitive effect on the aging 

Stabilizers are among the group of additives mixed into polymers during production or in structural component production to cmitrol and adjust their processing or utility properties. Basically, stabilizers can be categorized in groups as follows  

They provide protection during manufacture, molding, and use against the oxidative effect of oxygen and other oxidants. These are for the most part molecules that stop the chain reaction of the auto-oxidation process and are capable of forming highly stable, mesomerically stabilized, radicals. Without further additions, these stabilizers are consumed irreversibly in the course of the reaction. 

These additives significantly improve the efficacy of primary stabilizers on the basis of synergetic effects. Costabilizers reduce the hydroperoxides to take them out of the auto-oxidation process. These stabilizers (e.g. organic phosphites) are also irreversibly consumed depending on stress load levels. 

These stabilizers are used to increase the light resistance of plastics so they can be exposed to outdoor weather conditions during use. Two types of photoprotectants are used UV absorbers and quenchers. 

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The ozone concentration in the troposphere during the daytime is typically about 1 pphm (parts per hundred million parts of air by volume) [20], Values up to 100 pphm were measured in some photochemical smog areas. The molecular mechanism of the ozone aging of diene based elastomers was studied in detail and is well understood [19,21], Products or intermediates different from those arising in autoxidation or photo-oxidation of polymers were identified ozonides (3), zwitterions (4), diperoxides (5), polyperoxides (6), polymeric ozonides (7) and terminal aldehydes (8). Reactivity of aminic antiozonants (AOZ) with these species accounts for the protection of rubbers against atmospheric 03. AOZ must also possess antioxidant properties, because the free radical processes are concerted with ozonation due to the permanent presence of oxygen. 

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