Why do we need to add UV stabilizers and antioxidants to plastic products? Because plastics are affected by oxygen and light in nature, they will undergo a series of reactions, causing the compounds in the plastics to break, degrade and crosslink, leading to the destruction of plastic.
What is UV?
Ultraviolet is generated by excited outer electrons of atoms. It is calculated in units of nanometers (nm), and the wavelength range is 200-400nm. According to the different wavebands, it can be divided into UVA(320-400nm), UVB(280-320nm), and UVC(200-280nm).
|DESCRIPTION||WAVELENGTH RANGE (nm)|
|UVA||320 – 400|
|UVB||280 – 320|
|UVC||100 – 280|
The main source of ultraviolet in nature is the sunlight. Ultraviolet only accounts for 4.6% of the solar spectrum.
When sunlight passes through the atmosphere, the wavelength shorter than 290nm is absorbed by ozone. Therefore, UVC cannot pass through the atmosphere to reach the ground.
Ultraviolet radiation generally depends on conditions such as stratospheric ozone, clouds, altitude, the position of the sun’s height (time of day and time of year), and reflection. Therefore, there are different UV exposures in different geographical locations.
1 kLangley ( KLY ) = 1 kcal/cm2= 41.84 MJ/m2
1 kLangley/year = 1.33 W/m2
Data provided by the Surface Radiation Budget Project at NASA Langley Research Center
UV radiation is measured annually by units of Kilo Langley (Kilo Langley) and maps all over the world are drawn.
We calculate the service duration of plastics according to the radiation value of different regions.
For example: In Australia, the annual UV radiation required for continuous outdoor use of plastic is 200 kcal/cm2 ( 200KLY ), while in France it is 100 kcal/cm2 ( 100KLY ).
The average value in central Western Europe is 100 kcal/cm2 ( 100KLY ).
All of EyouAgro products with UV stabilizers have an indicative value that allows you to understand their service duration under normal conditions. After using in a specific Kly region for a certain period, the retained strength should be at least 50%.
Please note that these values are only an indication, as there are many other conditions that would affect the results, such as cloud cover, atmospheric humidity, snow reflections, and altitude.
UV degradation of plastic
Different types of plastics are sensitive to different wavelengths of UV light. The sensitive wavebands of polypropylene are 290-300nm, 330 and 370nm. The sensitive wavebands of nylon is 290-315nm, and that of PVC homopolymer is 320nm.
|UV Wavelength Sensitivity of Polymers (nm)|
|Material||Activation spectra maxima|
|Styrene Acrylonitrile||290, 310-330|
|Polypropylene||290-300, 330, 370|
|PVC copolymer||330, 370|
Ultraviolet has a strong penetrating ability, about 98% of UVA can penetrate the ozone layer to reach the surface of the earth.
UVA is the main cause of plastic aging. Many synthetic and natural polymers are attacked by UV. Therefore, products or materials made of polymers without UV stabilized will eventually change in color, chalking， or cracking, which will further affect their use. This polymer UV degradation is related to ultraviolet light and is very obvious in materials and equipment exposed to sunlight.
Continuous exposure to UV may be a serious problem. Usually, we need to provide UV stabilizers and antioxidants in the production of plastic products to prevent this phenomenon. This measure is to prevent “photodegradation” which is a chemical process that occurs when UV radiation from artificial light sources or the sunlight destroys chemical bonds in polymers.