Polycarbonate sheet will yellow, theoretically all plastic sheet will yellow, but through special modification or add specific additives and other methods, can make some plastic anti-yellowing performance significantly improve, extend the time of yellowing. Polycarbonate sheet yellowing this is mainly because of its molecular structure in the ultraviolet radiation, high temperature, high humidity environment prone to photo-oxidation, degradation and hydrolysis reactions, the production of improper processing technology such as temperature control is not good, raw materials mixing uneven will also leave hidden problems, coupled with the use of contact with chemicals, cleaning and maintenance of improper factors will lead to the phenomenon of yellowing of polycarbonate sheet.
Reasons for the yellowing of polycarbonate sheet
Aging factors: polycarbonate plate long-term exposure to the outdoor environment, by the continuous irradiation of ultraviolet radiation, the molecular structure will gradually change, triggering the photo-oxidation reaction, which leads to the yellowing of the plate. Generally speaking, the longer the use of time, the greater the possibility of yellowing, the more obvious the degree. For example, some of the outdoor polycarbonate canopies that have been used for many years, there may be a more obvious yellowing phenomenon.
Temperature factors: If the polycarbonate plate is in a high temperature environment for a long time, or experience frequent temperature changes, it may accelerate its internal molecular chain breakage and degradation, which in turn leads to yellowing. For example, polycarbonate sheets used in some high-temperature industrial environments are more likely to yellow than those used in room temperature environments.
The influence of chemical substances: polycarbonate plate contact with certain chemical substances, such as organic solvents, acids and alkali substances, etc., may be a chemical reaction that destroys its molecular structure, causing yellowing. For example, if the cleaner containing organic solvents directly wipe the polycarbonate plate, it may lead to yellowing of the surface of the plate.
Processing problems: In the production and processing of polycarbonate sheets, if the process is not properly controlled, such as uneven mixing of raw materials, processing temperature is too high or too long, etc., it may cause stress or defects inside the sheet, and these factors will also affect the stability of the sheet, making it more prone to yellowing in the process of use.
How to mitigate the yellowing of polycarbonate sheets
Producers: use superior quality and good stability of polycarbonate raw materials and additives during production, ensure that the quality and additive quantity of ultraviolet absorbers, antioxidants and other additives meet the standards, and enhance the anti-yellowing ability of the sheet from the source. At the same time in the polycarbonate plate surface supply a layer of anti-uv coating can also effectively alleviate yellowing.
Customers: regularly remove the surface of the dust, stains, etc., avoid the use of corrosive cleaning agents, so as not to damage the surface of the plate. You can regularly apply UV and antioxidant protectants to the polycarbonate sheet, and you can also coat the surface of the sheet to improve the weather resistance and anti-yellowing properties of the sheet.
What properties are affected by the yellowing of polycarbonate sheets
The optical properties of polycarbonate sheet will decline
Reduced light transmittance: polycarbonate sheet originally has a high light transmittance, can be comparable with glass, but after yellowing, its light transmittance will be significantly reduced, so that the light through the light becomes dim, uneven, affecting the lighting effect. For sunroom polycarbonate plate yellowing, indoor lighting will become less bright and transparent than before.
Colour distortion: yellowing will lead to changes in the refraction and scattering of light by the polycarbonate sheet, causing the colour of the light transmitted to deviate and affecting the visual effect. If it is used in the display or lighting field, it may make the colour of the displayed items or the lighting environment distorted and unable to present the real colour.
The mechanical properties of polycarbonate sheets will weaken
Reduced tensile strength: After yellowing polycarbonate sheets, changes in their internal structure will reduce their tensile strength and make them more susceptible to deformation when subjected to tensile forces. If used in structures that need to withstand tensile force, such as the support structure of some buildings or hanging parts, there may be potential safety hazards.
Changes in hardness: The hardness of polycarbonate sheets may also be affected, either by hardening or softening. Hardening can make the sheet brittle and fragile, while softening can cause it to become less resistant to abrasion and compression, and prone to scratches and dents.
The chemical properties of polycarbonate sheets can deteriorate
Weathering deterioration: The yellowing of polycarbonate sheets is often the result of aging due to long-term exposure to the environment and the influence of ultraviolet light, oxygen, temperature and other factors. After yellowing, its weather resistance will further deteriorate, more vulnerable to external environmental factors, accelerate the aging process, shorten the service life.
Reduced chemical stability: changes in the molecular structure may make the chemical stability of polycarbonate sheets reduce the tolerance of acids, alkalis, organic solvents and other chemical substances weakened, more prone to chemical reactions, thereby further damaging the performance of the sheets.
How to remove yellow spots on polycarbonate sheet?
Physical method
- Choose ordinary white toothpaste, squeeze the toothpaste on the yellow spots and gently wipe with a soft damp cloth or sponge.
- Mix baking soda and water in the ratio of 1:2 to make a paste. Apply the paste to the yellow spots on the polycarbonate sheet and gently wipe it with a soft cloth or brush, then rinse it with water. Baking soda can effectively remove some yellow spots and dirt.
- If the yellow spots are stubborn, choose the right thickness of sandpaper for sanding. Generally use coarse sandpaper to initially sand the yellow spot area, and then switch to fine sandpaper for fine sanding, so that the surface of the plate to restore smooth.
Chemical method
- Use a cotton ball or soft cloth dipped in an appropriate amount of alcohol, gently wipe the yellow spots on the polycarbonate plate. Alcohol can dissolve some oil and organic stains, for the yellow spots caused by grease or other organic matter attached to have a better cleaning effect.
- Dilute white vinegar and wipe the yellow spots with a soft cloth dipped in the solution. The acidic component in white vinegar can break down some of the dirt and yellow spots.
- Purchase a cleaner specifically designed for polycarbonate panel cleaning and follow the instructions.