Light stabilizer is a kind of can inhibit or reduce light on plastic degradation, increased photostability of plastic material. But most of them can absorb ultraviolet light, so it is also called ultraviolet absorbent. Ultraviolet rays from the sun are the main causes of aging of polymer materials. Although the ultraviolet ray only accounts for about 5% of the energy of sunlight, but is very large, the chemical bond energy sufficient to destroy the polymer, the molecular chain rupture, crosslinking, cause canceration, its mechanical properties at the same time, it is also the colour of change.
  1.Classification of light stabilizer. Although the light stabilizer varieties, such as the mechanism to points, can be divided into four categories: light shielding agent, also known as sunscreens, is a kind of material that can reflect or absorb ultraviolet light, can make plastic products and ultraviolet intermediate shielded, partition, reduce ultraviolet ray projection effect, harm to product internal unaffected by UV, effectively inhibited the light aging. Commonly used to shield agent with carbon black, Zinc Oxide, titanium oxide. The carbon black is the highest efficiency of the light shielding agent; ultraviolet absorbent. This is the most commonly used around the stabilizer, is the main body of light stabilizer. They are a class of strong, can selectively absorb ultraviolet light, and energy conversion, in the form of heat or harmless low-energy radiation, the energy release or consumption of material. The commonly used UV absorber with salicylic acid ester, two benzophenone, the latter is the most widely used maximum yield, wide, absorption wavelength of UV absorber, it almost does not absorb visible light, sleet most resin good biocompatibility; quenching agent, contrary to shield or absorption of ultraviolet ray, the polymer molecule is absorbed, make its are in unstable "excited", in order to prevent further damage to the polymer chain, need to quickly and effectively to excited state molecular "quenching" to return to the lower energy state, thereby protecting the polymer stabilization. Quenching agents commonly used is mainly organic complexes of Ni; free radical trapping agent, it is a kind of novel light stabilizers, which are a class of sterically hindered piperidine derivatives light stabilizer, referred to as the hindered amine to stabilizer. These compounds almost do not absorb ultraviolet light, but can capture free radicals, this free radical polymer absorbing UV light, resulting in decomposition produces auto oxidation reactions, and radical scavenger can capture the free radicals, prevent the chain reaction continues, and the formation of stable compounds. Common free radical trapping agent sebacic acid diester, phosphite ester, three.
  2.The principles of the light stabilizer. In practical application, selection of light stabilizers is often not easily, can look at several points. According to the maximum sensitivity wavelength polymers, used in this wavelength range as possible varieties of high absorption coefficient; must consider other additives, such as antioxidant, heat stabilizer, lubricant, coloring agent on the effect of light stabilizer effectiveness, which should not be reduced light stabilizer effect; some light stabilizer has a certain toxicity, in the stabilizer for what kind of products should be seriously considered plastic products should not be added to food contact.