Light stabilizers is polymer products of additives, such as plastic, rubber, paint and ynthetic fibers. It has functions of shielding or absorbing UV energy, quenching of singlet oxygen, making hydrogen peroxide breaks down into non-active substances and so on. It makes polymer exclude or slow the possibility of photochemical reaction, block or delay light aging process under light irradiation. Therefore to reach the purpose of extending the life of polymer products.
The mechanism of light stabilizers can be divided into the following categories:
1 Light Shield Agent
This is a class of substances covered or reflected ultraviolet and make light cannot penetrate inside the polymer, thus it plays a role in protecting polymers. There are carbon black and titanium dioxide of inorganic pigments light shield agent, phthalocyanine blue and phthalocyanine green of organic pigments light shield agent in OKCHEM, but carbon black works best.
2 The UV Absorber
It can effectively absorb the ultraviolet wavelength of 290~410nm, but rarely absorb visible light, which itself has a good thermal and light stability. According to its chemical structure, it can be divided into O-diphenyl methyl ketone, benzo-triazole class, salicylic acid esters, triazine and replacing acrylonitrile class. As an auxiliary light stabilizer used with hindered light stabilizer together, especially in polyolefin or paint.
3 Free Radical Scavenger
These light stabilizers can capture activity free radical generated in the polymer, thus inhibiting oxidation processes to reach the goal of light stabilizer. It mainly hindered amine light stabilizers (HALS). It is the most promising new type of high efficiency light stabilizer. Its annual average growth rate is 20%~30% in the international.
4 Quenching Agents
It can accept energy absorbed by plastic chromophore, and spread the energy in the form of heat, fluorescent or phosphorescen, so as to protect the polymer from damaging of ultraviolet rays. It has a good effect on the stability of polymer and used in films and fibers.
5 Hydroperoxides Decomposers
It is a kind of hindered amine light stabilizers. During storage and processing, polymer to produce hydroperoxides. This results in oxidative degradation of polymer optical. Hydrogen peroxide decomposers that breaks down peroxides, generate stable nitrogen-oxygen free radicals, and further capture of free radicals, thus inhibiting degradation of polymers.
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