For most plastic products, especially those that are used outdoors, it is inevitable to be vulnerable to negative environmental effects such as ultraviolet (UV) light, oxygen, temperature,… The frequent exposure to those elements leads to the transformation in the chemical structure of polymers, resulting in the degradation of end products’ mechanical properties. UV stabilizers in plastic: What are they and how many types do they have? As one of the most effective solutions to the UV degradation of plastic, UV stabilizers (anti UV additives) are chemically formulated to absorb UV light’s energy, thus minimizing the contact between plastic surface and the UV rays. Normally, UV stabilizers are embedded into polymer combinations during the mixing phase to ensure it will disperses well on products’ surfaces. Interestingly, there are at least 3 types of UV stabilizers in plastic, which differ from each other regarding the mechanism of action. Absorbers Absorbers function by absorbing UV light, which may be absorbed by chromophores and change the harmful UV radiation into harmless infrared radiation or heat. Cost effective they might be, UV absorbers are most suitable for products with short-time exposure only. In the long run, this material is much less efficient. Some popular UV stabilizers of this type are: carbon black (which is the most common one thanks to its black color), rutile titanium oxide (which is effective in the 300 – 400 nm range but work less efficiently in the short wavelength ranging below 315), hydroxybenzophenone, hydroxyphenyl benzotriazole (this type is suitable for neutral or transparent applications but not very useful in thin parts below 100 microns), benzophenones for PVC, benzotriazoles and hydroxyphenyl triazine for polycarbonate, oxanilides for polyamides. Quenchers Another type of UV stabilizers in plastic are quenchers, which are also called light stabilizers. They work by quenching molecules that are over-excited during the UV absorption, and transfer the energy absorbed into heat. Generally, compared to its counterparts, quenchers are considered as the least effective methods of blocking UV radiation. HALS When it comes to the most effective UV stabilizers in plastic, HALS (Hindered amine light stabilizers) will undoubtedly be that one. Unlike its fellows, which work in the absorption phase of polymer, HALS take place in the early of the polymer degradation process. When free radicals are formed, it then traps them, thus preventing them from doing any damages to end-products. However, the chosen HALS must be compatible with the polymer, or else it can cause die build up at the extruder die and inefficient polymer protection. Interested? Find out more here!
