The effect of radiant energy on pigments. The effect of electromagnetic energy on pigments is not as severe as that on vehicles.
The dispersion prepared with untreated anatase titanium dioxide and any organic binder has severe chalking effect. This is because titanium dioxide is photoreduced to a lower oxidation level. This process is caused by the oxidation of the surrounding linking material by the highly reactive nascent oxygen released after the action of ultraviolet rays. Titanium dioxide can be re-oxidized to its original state by oxygen in the atmosphere, but the deterioration of the link material can no longer be restored, resulting in rapid pulverization.
Since the rutile titanium dioxide with relatively high density has a tendency to absorb ultraviolet rays, although it still has a photoreduction effect, it provides a certain protective effect on the linking material. The effect of titanium dioxide on ultraviolet rays can be greatly reduced after surface treatment (such as with aqueous salts of aluminum and silicon). Assuming that the photosensitivity of titanium dioxide occurs at a certain position on the surface of the particle, after surface treatment, due to the occupation of these positions, the photochemical reduction caused by ultraviolet light is prevented, thereby greatly eliminating the oxidation of the linking material. and recession.
Pure zinc sulfide pigment has a tendency to yellow due to photochemical activity in the binder system, so adding a certain amount of cobalt can greatly improve its light resistance when manufacturing zinc sulfide pigment.
Luminescent pigments absorb radiant energy and then emit this energy after converting it to a longer wavelength. Since most luminescent pigments can be activated by near-ultraviolet and visible violet wavelengths, the wavelengths can emit a full-color spectrum. What produces brightness when activated is called fluorescence. The luminance that remains after the activation is stopped is called phosphorescence. Inorganic fluorescent pigments (phosphors) used in industry are generally zinc sulfide or zinc cadmium sulfide. Inorganic phosphorescent pigments are generally zinc cadmium sulfide or calcium strontium sulfide type and so on.
The above situations illustrate the relationship between electromagnetic energy and pigments.
