Classification of light stabilizers

1. Light shielding agent: This is a kind of material that can shield or reflect ultraviolet rays, so that light

can not penetrate into the polymer, thus can protect the polymer. Light shielding agents include inorganic

pigments such as carbon black, titanium oxide and organic pigments such as phthalocyanine blue and

phthalocyanine green, among them carbon black has the best shielding effect.

2.Ultraviolet absorbent: It can effectively absorb ultraviolet radiation with wavelength of 290-410 nm, but

rarely absorb visible light. It has good thermal stability and light stability. According to its chemical structure,

it can be divided into o-hydroxybenzophenones, benzotriazoles, salicylates, triazines and substituted

acrylonitriles. It can be used as auxiliary light stabilizer and hindered light stabilizer, especially in polyolefins

or coatings.

3. Quenching agent: It can accept the energy absorbed by the chromophore in plastics and disperse the

energy in the form of heat, fluorescence or phosphorescence, thus protecting the polymer from ultraviolet

damage. It has good stabilization effect on polymers and is mostly used in thin films and fibers. It is mainly

some divalent organic nickel chelates. Organic nickel light stabilizers have good properties, but due to

the toxicity of heavy metal ions, they may be replaced by other non-toxic or low toxic quenchers.

4.Free radical scavengers: These light stabilizers can capture the active free radicals generated in

polymers, thus inhibiting the photooxidation process and achieving the goal of light stabilization. Mainly

hindered amine light stabilizer (HALS). It is the most promising new type of high-efficiency light stabilize

r with an average annual growth rate of 20%-30% in the world.

5. Hydroperoxide decomposer: one of the hindered amine light stabilizers. Hydroperoxide can be produced

during storage and processing, which leads to photooxidation degradation of polymers. Hydroperoxide

decomposer can decompose peroxides, generate stable nitrogen-oxygen free radicals, and further capture

free radicals, thus inhibiting polymer degradation.