This report reviews various compounds that protect polymers against deterioration, Polymers are exposed to many degradative effects of which heat, oxygen, ozone, and ultraviolet light are the most important. The chemical additives that counteract the above effects are antioxidants, antiozonants, and ultraviolet stabilizers.
Antioxidants benefits and side effects. For example, free radicals (also called pro-oxidants, as opposed to anti-oxidants) are used by the immune system to wipe out bacteria that could cause infections. ( 2) When the balance of free radicals and antioxidants gets out of whack, oxidative stress can occur.
Antioxidants. These changes are the result of oxidative degradation caused by free radicals which form through hydrogen abstration or homolytic scission of carbon-carbon bonds when polymers are exposed to heat, oxygen, ozone, or light. These changes can have a dramatic effect on the service life and properties of the polymer.
The amount of antioxidants in supplements may be so high compared with that in the diet that it leads to a toxic effect. Other nutrients may be present in fruits and vegetables that work in sync with antioxidants and are necessary to provide a protective effect.
A comprehensive review of elastomer oxidation and the role of antioxidants and antiozonants is available (Hong, 2004). 9.4.1 Degradation of Rubber Oxidation of elastomers is accelerated by a number of factors including heat, heavy metal contamination, sulfur, light, moisture, swelling in oil and solvents, dynamic fatigue, oxygen, and ozone.
Antioxidants (and antiozonants) react with these radicals to terminate the chain reaction causing oxidation of polar polymer systems; thereby prolonging the serviceability of a rubber article. Antioxidants also react with hydrocarbon radicals when they are formed. In doing so,
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