Introduction
Rubber compounding is a complex process that involves the use of various chemicals to achieve desired properties. One of the essential chemicals used in rubber compounding is antioxidants. Antioxidants are compounds that protect the rubber from oxidation, which can lead to degradation and failure of the rubber product.
Types of Antioxidants
There are two types of antioxidants used in rubber compounding: primary and secondary antioxidants. Primary antioxidants are added to the rubber compound during mixing, while secondary antioxidants are added during processing.
Primary Antioxidants
Primary antioxidants are compounds that react with the free radicals generated during the rubber vulcanization process. These antioxidants prevent the formation of new free radicals and protect the rubber from oxidation. The most commonly used primary antioxidants in rubber compounding are phenolic antioxidants, such as 2,6-di-tert-butyl-4-methylphenol (DBP).
Secondary Antioxidants
Secondary antioxidants are compounds that react with the free radicals generated after vulcanization. These antioxidants scavenge the free radicals and prevent them from attacking the rubber. The most commonly used secondary antioxidants in rubber compounding are amine antioxidants, such as N-phenyl-2-naphthylamine (PNA).
Benefits of Antioxidants
The addition of antioxidants to rubber compounds provides several benefits, including:
- Improved heat and ozone resistance
- Extended service life
- Reduced cracking and degradation
- Improved mechanical properties
Factors Affecting Antioxidant Performance
Several factors can affect the performance of antioxidants in rubber compounds, including:
- Chemical structure of the antioxidant
- Concentration of the antioxidant
- Processing conditions
- Type and amount of other chemicals in the rubber compound
Conclusion
Antioxidants play a vital role in rubber compounding, providing protection against oxidation and extending the service life of rubber products. Understanding the types of antioxidants, their benefits, and the factors that affect their performance is essential in achieving optimal rubber compound properties.
References
1. S.N. Chattopadhyay, Rubber Chemistry and Technology, 92 (2019) 1-28.
2. J. Wypych, Handbook of Polymers, 2nd ed., ChemTec Publishing, 2016.