In plastics, ultraviolet rays (UV rays) can lead to a variety of undesirable changes. These include color changes, embrittlement, cracking, and even loss of strength and dimensional stability. To counteract these effects of UV radiation, two main types of UV protection agents are used: light stabilizers and UV absorbers.
Light Stabilizers
Light stabilizers are added as additives to plastics to enhance their resistance to UV rays. They work by preventing or delaying the photochemical breakdown of polymer chains triggered by UV radiation. This occurs through various mechanisms, including:
- Radical scavengers: This type of light stabilizer reacts with the free radicals generated by UV radiation, thus preventing their impact on the polymer.
- Absorption of UV light: Some light stabilizers absorb UV rays and convert them into heat, minimizing their effects on the polymer.
UV Absorbers
UV absorbers absorb UV rays and convert them into harmless heat energy, thereby protecting the polymer from the harmful effects of UV radiation. This type of UV protection agent is often used as a surface-active agent to shield the plastic’s surface from UV rays. There are two types of UV absorbers:
- Organic UV absorbers: This type is frequently used in thermoplastic plastics as they remain stable at higher temperatures. They absorb UV rays through electron transitions in organic molecules.
- Inorganic UV absorbers: This type is typically employed in thermosetting plastics. They absorb UV rays through a compound between metal ions and molecules.
Conclusion
Light stabilizers and UV absorbers employ different mechanisms to protect plastics from the harmful effects of UV radiation. While light stabilizers delay or prevent the photochemical breakdown of polymer chains, UV absorbers absorb UV rays and convert them into harmless heat energy. Both types of UV protection agents are crucial to ensure the durability and integrity of plastic products exposed to UV radiation.
