Antioxidants are essential additives widely used in the thermal processing and utilization of plastics, aiming to mitigate the effects of thermal oxidation and degradation.

Antioxidants play a critical role in protecting plastics during processing and service life by preventing oxidative damage. This extends product durability and enhances overall performance.

Heating plastics can trigger oxidation reactions, causing material damage. When plastics are exposed to heat, oxidation can lead to chain scission, cross-linking, and carbonyl formation, resulting in brittleness, discoloration, and loss of mechanical properties.

Antioxidants counteract these effects by scavenging free radicals formed during oxidation, disrupting the propagation cycle of thermal oxidation. This reduces or prevents material degradation.

Antioxidants are primarily classified into the following types:

1. Primary Antioxidants: These include hindered phenols and amine compounds. They act by directly reacting with free radicals or donating hydrogen atoms to form inert compounds, terminating the peroxide chain reaction to protect plastics.
2. Secondary Antioxidants: Known as "preventive antioxidants," these include phosphite antioxidants. They react with peroxide groups to produce inert, non-free radical compounds, stopping the chain reaction. Secondary antioxidants are often used together with primary antioxidants for synergistic effects.

1. Maintaining Mechanical Properties: Antioxidants help preserve the mechanical strength and flexibility of plastics during high-temperature processing, preventing degradation.
2. Color Preservation: Antioxidants prevent discoloration due to oxidation, ensuring that the plastic retains its original color.
3. Extended Service Life: By mitigating the effects of thermal oxidative degradation, antioxidants prolong the lifespan of plastic products.

As a result, antioxidants provide protection for plastics at various stages, maintaining their performance and appearance throughout their lifecycle.