Can UV light penetrate through plastic or glass?

The wavelength range of ultraviolet light is generally in the range of 10-400nm, which does not belong to the category of visible light, so whether it can penetrate cannot be judged by whether the material is transparent or not. Transparent plastic or glass can block part of the UV light, but the degree of blocking can be very different.

In principle, whether a light can pass through a material depends on whether the energy of this light can be absorbed by the material, each material has its own intrinsic frequency of electrons in the molecules, when the frequency of light and the intrinsic frequency of these electrons are the same, the light energy of this light will cross the energy gap to activate the low-energy state of the electrons to the high-energy state, thus converting the light energy into other forms of energy.

In addition the ability to resist light is also proportional to the concentration and thickness of the light-absorbing material, which can be referred to Beer's Law (Beer's Law).

Compared with visible light, ultraviolet energy is relatively large, so to allow the passage of ultraviolet light is not absorbed, the need for a relatively large energy gap of the material to do. Most of the glass and plastic do not meet this condition, so it is difficult to let ultraviolet light, especially the lower wavelength part of the penetration, generally speaking, the resistance rate is more than 90%.

Ultraviolet light is divided according to wavelength: near ultraviolet (UVA), far ultraviolet (UVB) and ultra-short ultraviolet (UVC). Although ultraviolet light has a penetrating effect on human skin, and the longer the wavelength of ultraviolet light, the greater the danger to human skin, but can not penetrate non-transparent plastic, even transparent plastic or ordinary glass, attenuation is also very large, so ultraviolet lamps must be made of high-purity quartz glass.

The earliest method of adding UV resistance is the coating process, which is simple and crude, by directly coating the surface of the PC resilient board for canopies with UV resistance agents to achieve. Although this adding process can also resist ultraviolet rays, but it is easy to be affected by the outside world, rain and sand washing will make the anti-UV coating loss a lot, and will soon wear out. The result is that the PC resistance board lost protection, a few months will be aging. Therefore, this backward process was also eliminated.

And then, the industry appeared mixed co-extruded add process, this process is in the production of PC endurance board before the PC raw materials and UV raw materials mixed together to achieve the effect of anti-UV. This process than the coating process to extend the life of the plate, but is limited to the principle of mixed co-extrusion, PC raw materials and anti-UV particles are unevenly distributed, both PC performance or anti-UV performance can not be played to the maximum, life expectancy of about 5 years.

In summary: UV can not penetrate any film / glass / paper, is determined by its light wave frequency. Daily test UV aging equipment is: uv light chamber.