Secondary antioxidants, such as phosphites and thioethers, decompose hydroperoxides into non-radical, non-reactive, and thermally stable products. Therefore, auxiliary antioxidants are also called hydroperoxide decomposers. Phosphites and thioethers antioxidants are widely used hydroperoxide decomposers. Phosphites are most effective at the high temperatures of melt processing operations, while thioethers work best in the solid phase at long-term use temperatures. Secondary antioxidants are used together with primary antioxidants to increase the stability of polymers.
Phosphite Antioxidants are secondary antioxidants that decompose peroxides and hydroperoxides into stable non-radical products. They are extremely effective stabilizers during processing and are often used in combination with primary antioxidant to provide good heat stability, color stability, process stability and weatherability to polymers.
For more than 30 years, TINTOLL has been committed to providing innovative high-performance light stabilizers and antioxidant solutions to meet the growing and changing technical needs of the global plastics market.
TINTOLL's various antioxidants play an important role in inhibiting and delaying the oxidation and degradation of polymeric materials. TINTOLL is available in a variety of physical forms as well as standard and custom blends. The choice of antioxidant depends on factors such as compatibility, color and thermal stability, volatility and stabilizer efficiency.
Secondary antioxidants retard oxidation by preventing the proliferation of alkoxy and hydroxyl radicals by decomposing hydroperoxides to yield nonreactive products. These polymer antioxidants are typically used in a synergistic combination with primary antioxidants.
Organophosphates
Acting as secondary antioxidants, organophosphates reduce hydroperoxides to alcohols, converting themselves to phosphonates. They also provide color stability, inhibiting the discoloration caused by the formation of quinoid reaction products which are formed upon oxidation of phenolics. Tris-nonylphenyl phosphite (TNPP) is the most commonly used organophosphate followed by tris(2,4-di-tert-butylphenyl)phosphite.
Thioesters
Derived from aliphatic esters of B-thio dipropionic acid, thioesters act as secondary antioxidants and also provide high heat stability to a variety of polymers. Thioesters function as secondary antioxidants by destroying hydroperoxides to form stable hexavalent sulfur derivatives.
Thioesters act as synergists when combined with phenolic antioxidants in polyolefins.
Deactivators
Metal deactivators combine with metal ions to limit the potential for chain propagation. Metal deactivators are commonly used in polyolefin inner coverings in wire and cable applications where the plastic comes in contact with the metal.
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