Oxygen, heat, sunlight and water are present throughout the life cycle of the plastic article. During the manufacturing conditions, polymer chains undergo cleaving by oxidation, chain branching and/or crosslinking, which can lead to a breakdown of the polymer structure. A variety of antioxidants are used to protect the plastic and maintain its molecular integrity.
Two main strategies exist to protect polymers from thermal degradation.
Primary or phenolic antioxidants interfere with chain propagation by terminating the free radical. Phenolic antioxidants act as H-donors, offering to the peroxy radical an easily abstractable hydrogen, avoiding the abstraction of hydrogen from the polymer backbone.
Secondary or phosphite antioxidants, transform hydroperoxides into non-radical, non-reactive, thermally stable products. Secondary antioxidants protect primary antioxidants during processing.
The combination of both antioxidant classes achieves a synergistic effect and is the generally accepted method of stabilization. 3V commercializes primary and secondary antioxidants under the ALVINOX trade name.