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In modern industry and daily life, coating technology plays a crucial role. Especially in the field of self-cleaning, the application of coatings has greatly improved the cleaning efficiency and durability of object surfaces. This article will delve into the principles and technical details of how the self-cleaning effect of coatings is achieved.
Self-cleaning coatings mainly rely on superhydrophobic or superhydrophilic principles, as well as the novel Smooth Covalently Attached Liquid Surfaces (SCALS) technology.
Superhydrophobic coatings form a micro-nano-scale rough structure that prevents water droplets from spreading on the surface, causing them to form spheres instead. Contaminants in the air cannot be wetted by the water droplets and are therefore easily washed away by rain. This principle is similar to the self-cleaning effect of lotus leaves and is therefore also known as the "lotus effect".
The preparation of superhydrophobic coatings typically involves the use of nanoparticles, such as nano-alumina (Al₂O₃). These nanoparticles form a micro-nano-scale rough structure on the coating surface, making the coating surface superhydrophobic. Meanwhile, the photocatalytic activity of the nanoparticles can decompose organics into easily washable substances, further enhancing the self-cleaning effect.
Contrary to the superhydrophobic principle, superhydrophilic coatings cause water droplets to quickly spread out on the surface, forming a thin water film. This water film can carry away contaminants on the surface, achieving a self-cleaning effect. Superhydrophilic coatings are commonly used on materials such as glass and ceramics to make self-cleaning glass and tiles.
SCALS technology is a novel self-cleaning coating technology developed by researchers at the University of Sydney in Australia. This technology chemically binds oil molecules to solid surfaces, maintaining their liquid properties, thereby creating a surface that resists the attachment of dirt, scale, ice, and bacteria. The liquid-like molecules in SCALS coatings can make contaminants very slippery on the surface, while also improving heat transfer efficiency and preventing the accumulation of scale.
Nanoparticles play a crucial role in self-cleaning coatings. By controlling the size, shape, and distribution of nanoparticles, the self-cleaning performance of the coating can be precisely regulated. For example, in superhydrophobic coatings, the micro-nano-scale rough structure formed by nanoparticles is key to achieving superhydrophobicity.
The chemical composition of self-cleaning coatings has a significant impact on their performance. In SCALS technology, researchers use materials such as organosilicon and polyethylene glycol to manufacture coatings. These materials decompose into harmless byproducts in the environment and are environmentally friendly. Meanwhile, by optimizing the ratio and reaction conditions of these materials, the self-cleaning performance and durability of the coatings can be further improved.
The preparation process also has an important impact on the performance of self-cleaning coatings. For example, in the preparation of superhydrophobic coatings, it is necessary to precisely control the dispersion of nanoparticles and the curing conditions of the coating. In the preparation process of SCALS technology, it is necessary to precisely control the length and attachment density of liquid molecules to ensure that the coating achieves optimal performance.
Self-cleaning coatings have a wide range of applications in multiple fields. For example, in the construction field, self-cleaning glass and tiles can reduce cleaning and maintenance costs; in the transportation field, self-cleaning coatings can reduce the accumulation of dirt on vehicle bodies, improving their aesthetic appeal and durability; in the consumer goods field, self-cleaning coatings can be applied to appliances, furniture, and other products, enhancing their user experience and lifespan.
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