Introduction
Antioxidants are important additives used in plastics to prevent thermal and oxidative degradation during processing and long-term use. When plastics are exposed to heat, oxygen, or ultraviolet radiation, polymer chains may degrade, resulting in discoloration, brittleness, and loss of mechanical properties.
To maintain the stability and durability of polymer materials, various types of antioxidants are added to plastic formulations.
Antioxidants used in plastics can generally be classified into several categories based on their chemical structure and function.
1. Phenolic Antioxidants
Phenolic antioxidants are the most widely used antioxidants in plastic materials.
Common examples include:
- Irganox 1010
- Irganox 1076
- BHT (Butylated Hydroxytoluene)
These antioxidants work by scavenging free radicals, which prevents chain reactions that cause polymer degradation.
However, BHT is gradually being used less frequently due to its:
- Low molecular weight
- High volatility
- Tendency to cause yellowing and discoloration in some plastics
2. Phosphite Antioxidants
Phosphite antioxidants are commonly used as secondary or auxiliary antioxidants. They work by decomposing hydroperoxides formed during polymer oxidation, thereby improving the overall antioxidant system.
Common phosphite antioxidants include:
- TNPP (Tris Nonylphenyl Phosphite)
- Irgafos 168
- Ultranox 626
- Mark PEP-36
- Cyanox 2777
These antioxidants are typically used together with phenolic antioxidants to enhance stabilization performance.
3. Sulfur-Based Antioxidants
Sulfur-containing antioxidants are less widely used compared with phenolic and phosphite antioxidants, but they still play a role in certain applications.
Typical products include:
- Sumilizer TP-D
- TM610
- Mark AO-23
- Irganox 1035
- Irganox 1192
- Irganox 1520
These antioxidants can improve the long-term thermal stability of polymers, especially in combination with other antioxidant systems.
4. Metal Ion Passivators
Metal ion passivators are used to prevent polymer degradation caused by trace metal ions that may catalyze oxidation reactions.
The most common type is bis-salicyldiamine compounds.
Representative products include:
- Irganox MD1024
- Nouguard XL-1
These additives are particularly useful in applications where plastics may come into contact with metal surfaces or metal residues.
5. Compound Antioxidants
Compound antioxidant systems have become one of the major development trends in the plastic additives industry.
These systems combine different types of antioxidants to achieve higher stabilization efficiency.
Typical composite antioxidants consist of combinations such as:
- Hindered phenolic antioxidants
- Phosphite antioxidants
- Thioester antioxidants
Some systems also combine hindered phenolic antioxidants with ultraviolet absorbers for enhanced protection.
Representative products include:
- Irganox B series
- Irganox LC
- Irganox LM
- Irganox HP
- Irganox XP
- Ultranox 815A, 817A, 875A, 877A
- Recyclestab 411 and 811 (used for recycled plastics)
These compound antioxidants provide improved processing stability and long-term durability.
6. Polyphenol Antioxidants
Polyphenol antioxidants, such as Wingstay L, are high-activity antioxidants known for their:
- High stabilization efficiency
- Low volatility
- Good thermal stability
These additives are often used in high-performance polymer systems.
7. Natural Antioxidants
Natural antioxidants are gaining attention due to their non-toxic and environmentally friendly properties.
Examples include:
- Vitamin E
- Tocopherols
These natural compounds provide antioxidant protection while meeting increasing demands for sustainable and safe additives.
Conclusion
Antioxidants are essential additives that protect plastics from thermal and oxidative degradation, helping maintain material performance during processing and long-term use.
Different types of antioxidants—such as phenolic antioxidants, phosphites, sulfur antioxidants, metal ion passivators, and compound antioxidant systems—are often used together to achieve optimal stabilization.
With the increasing demand for high-performance and environmentally friendly materials, the development of compound antioxidant systems and natural antioxidants is becoming an important trend in the plastics industry.
