In recent years, the reduction of the ozone layer will increase the ultraviolet rays reaching the earth's surface, thereby increasing the incidence of skin cancer. Therefore, the requirements for the development of UV protection agents are becoming stronger. TiO2 particles not only have small particle size (transparent), high activity, strong ability to absorb ultraviolet rays, but also have good decolorizing power, hiding power, non-toxic, odorless, and good dispersibility. These characteristics determine TiO2 has an important position in the field of cosmetics and is widely used in cosmetics, especially sunscreens. TiO2 can be stably and evenly dispersed in cosmetics, using its absorption of ultraviolet rays, so as to achieve the effect of preventing sun aging.
Titanium dioxide, also known as titanium oxide or titania, is the naturally occuring oxide of titanium,chemical formula TiO2. Due to its small particle size and high activity, titanium dioxide particles can reflect and scatter ultraviolet rays as well as absorb ultraviolet rays, thereby having a stronger blocking ability against ultraviolet rays.
According to the different wavelengths, ultraviolet rays are divided into short-wave regions 190-280nm, medium-wave regions 280-320nm, and long-wave regions 320-400nm. Ultraviolet rays in the short-wave region have the highest energy, but are blocked when passing through the ozone layer. Therefore, the ultraviolet rays in the medium-wave and long-wave regions are generally harmful to the human body.
The strong UV resistance of titanium dioxide is due to its high refractive index and high photoactivity. Its anti-ultraviolet ability and its mechanism are related to its particle size.
When the particle size is large, the blocking of ultraviolet rays is mainly based on reflection and scattering, and it is effective for ultraviolet rays in the medium wave region and the long wave region. The sun protection mechanism is a simple covering, which is a general physical sun protection, and the sun protection ability is weak.
As the particle size decreases, light can pass through the surface of the titanium dioxide particles, and the reflection and scattering of ultraviolet rays in the long-wave region are not obvious, while the absorption of ultraviolet rays in the medium-wave region is significantly enhanced. Its sun protection mechanism is to absorb ultraviolet rays, mainly absorbing ultraviolet rays in the mid-wave region.
It can be seen that the sunscreen mechanism of titanium dioxide for different wavelengths of ultraviolet rays is different. The blocking of ultraviolet rays in the long-wave region is mainly based on scattering, and the blocking of ultraviolet rays in the medium-wave region is mainly based on absorption.