It is widely used in shampoo, hair care shampoo, bath and various, skin care cream, paste, milk, lipstick and other nutritional cosmetics and hand soap, detergent, dishwashing detergent, hair dye, leather coat polish, softener, glue, topical ointment, pesticide and other products.
The most primitive photo-aging test is carried out under direct sunlight, such as the Florida 45° angle exposure test used in the United States. Due to the light-absorbing effect of ozone in the earth’s atmosphere, the high-energy ultraviolet rays below 295nm are basically filtered out after the sunlight passes through the atmosphere and reaches the ground. Therefore, the wavelength band where the ground sunlight has a strong effect on the photo-aging of the polymer coating is concentrated at 295~400nm. The shorter, the stronger the photoaging effect on the polymer coating may be. Affected by many factors such as season, time of day, altitude, sasobit sasol wax latitude, weather, air pollution, etc., the ultraviolet intensity of the ground sunlight may change.
The ozone layer absorbs ultraviolet light in the wavelength range below 320nm. With atmospheric pollution, the ozone layer is destroyed and the intensity of short-wave ultraviolet light reaching the ground is increasing year by year. The light aging results obtained by using different light sources may be inconsistent, mainly caused by the incomplete consistency of the wavelength distribution, intensity, environmental humidity, temperature and other conditions of the various light sources.
In addition to the yellowness index, the anti-aging performance of the cured film can also be characterized by investigating the absorption spectrum , gloss, haze, adhesion, mechanical properties, and thermodynamic mechanical behavior of the cured film. Hill has used dynamic The mechanical analysis method tracks the photo-aging process of the light-cured film1. Due to the universality of the photo-oxidation reaction in the photo-aging process, the change in the hydroxyl index or peroxide index in the coating is often taken as a basic parameter reflecting the photo-aging. Different structures of polymers can also characterize the photo-aging behavior according to the changes in the concentration of sensitive groups.
Coating photo-aging behavior and mechanism
The photo-aging of the organic coating is because the coating will absorb the light energy to act on the chemical bonds of the cross-linked network to cause cracking or some form of transformation. A superficial understanding can relate the common chemical bond energy in the coating to the wavelength of visible light. Except for the higher bond energy of OH and C–F bond and the lower corresponding light wavelength, the light wavelength corresponding to other common chemical bond energy falls on In the range of the ground positive spectrum, that is, the sunlight reaching the ground has enough energy to open the above-mentioned chemical bonds in the polymer.
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