What are the Types of Antioxidants in Polymers?

According to the mechanism of action, polymer antioxidants are categorized as primary antioxidants (free-radical scavengers), secondary antioxidants (Peroxide scavenger), and metal deactivators (complex-forming or chelating agents).

Primary antioxidants react quickly with free radicals and are therefore called "free radical scavengers". The primary antioxidants for most polymers are hindered phenols.

Secondary antioxidants, including phosphites and thioesters, react with hydroperoxides to produce non-radical products. They are especially useful in synergistic combination with primary antioxidants. Phosphites antioxidants are most effective during processing, protecting the polymer and the primary antioxidant. Thioester antioxidants can be used together with phenolic antioxidants to improve long-term thermal stability.