Causes of light damage to plastics: For most plastics, the sensitive wavelength that is most likely to cause damage is between 290-400nm. This is the ultraviolet region. The ultraviolet energy can destroy the chemical bonds of polymers, lead to luminescence oxidation or oxidative photodegradation, resulting in the deterioration of physical and mechanical properties. At the same time, the formation of carbonyl decomposition products and chromophores deepens its color change.

Action mechanism of light stabilizer:

(1) Light shielding agent: It can absorb or reflect ultraviolet light, so that the light cannot be directly emitted into the polymer, thus effectively inhibiting light aging. Such as TiO2 and ZnO.

(2) Ultraviolet absorber: It can strongly absorb ultraviolet light and transform its energy into harmless heat energy. Such as benzophenones and benzotriazole.

(3) Quenching agent: It can eliminate the excitation energy from the excited polymer molecule and return it to the low energy state. Mainly metal complexes.

(4) Free radical trapping agent: capture different free radicals to prevent or delay the photodegradation process. Such as hindered amine.

The selection principle of light stabilizer: it can effectively eliminate or weaken the destructive effect of ultraviolet light on the polymer without affecting other properties of the polymer; Good compatibility with polymer, non-volatile, non-migration, and non-extraction by water and solvent; Low absorption of visible light, no coloring, no discoloration; It is similar to the color of polymer, and does not change the color of polymer after adding.