How to resist photochemical degradation with the help of UV absorbers and light stabilizers?

As the name suggests, the main function of UV absorbers is to absorb UV energy. These compounds usually have a specific molecular structure and can efficiently capture specific wavelengths of UV light, especially short-wave UV light (UVA and UVB) that are harmful to humans and materials. Once these high-energy photons are absorbed, the electrons in the UV absorber molecules will be excited to a high-energy state, and then quickly release the energy harmlessly into the surrounding environment in the form of heat energy through internal conversion or intersystem crossing. This process effectively prevents UV energy from directly acting on components such as resins and pigments in the coating film, thereby avoiding the occurrence of photochemical degradation.

In the formulation of powder coatings, the selection of UV absorbers is crucial. An ideal UV absorber should have high absorption efficiency, good thermal stability and compatibility with the coating system. Common UV absorbers include benzotriazoles, benzophenones, triazines, etc., each of which has different absorption wavelength ranges and light stability performance. Formulators need to make reasonable combinations according to specific application requirements to achieve the best UV protection effect.

Unlike UV absorbers, light stabilizers protect coatings from photochemical degradation mainly by scattering or reflecting UV energy and capturing and stabilizing free radicals excited by UV. Such compounds usually contain large side chain structures that can effectively scatter UV photons and reduce their chances of directly acting on the coating. Light stabilizers can also slow down the aging of coatings by capturing free radicals generated by UV excitation and preventing free radical chain reactions.

The role of light stabilizers in powder coatings cannot be ignored either. They can not only enhance the UV resistance of coatings, but also improve the heat resistance, weather resistance and chemical stability of coatings. Common light stabilizers include hindered amines (HALS), benzoxazoles and benzophenone-triazole complexes. These compounds have their own characteristics. Some are good at scattering UV rays, while others are good at capturing free radicals. Formulators need to carefully select and adjust the type and amount of light stabilizers according to the expected performance and use environment of the coating.

In powder coatings for outdoor metal furniture, UV absorbers and light stabilizers do not exist in isolation, but work together to build a powerful light protection network. UV absorbers are responsible for absorbing and converting UV energy, reducing the chance of it directly acting on the coating film; while light stabilizers further consolidate the protective barrier of the coating film by scattering UV rays and capturing free radicals. This synergy not only improves the UV resistance of the coating, but also enhances the overall weather resistance of the coating film, allowing outdoor metal furniture to maintain long-term beauty and durability even in extreme environments.

Effectively integrating UV absorbers and light stabilizers into powder coating formulas requires sophisticated formula design and rigorous application practice. Formulators need to fully understand the performance characteristics of various UV absorbers and light stabilizers, and select appropriate compounds and their proportions based on the expected performance and use environment of the coating. Laboratory tests, such as accelerated aging tests and xenon lamp aging tests, are required to evaluate the UV resistance and weather resistance of the coating to ensure that the formula meets the design requirements. In the actual production process, the quality of raw materials, processing temperature and spraying process must be strictly controlled to ensure the stability and consistency of coating performance.

In terms of application practice, outdoor metal furniture manufacturers need to select appropriate powder coating formulas and spraying processes according to the material, shape and use environment of the furniture. For example, for furniture that needs to withstand high-intensity ultraviolet radiation, a coating formula containing high-efficiency anti-ultraviolet absorbers and light stabilizers should be selected; for furniture with complex shapes or that needs to maintain fine textures, appropriate spraying techniques such as electrostatic spraying or thermal spraying are required to ensure that the coating is evenly covered and fully cured.