Development of scratch-resistant and wear-resistant coatings: What are the suitable materials? What are the differences between them?
The traditional method to enhance the mechanical properties of coatings involves increasing the cross-linking density of the thin film. This is achieved through choices in altering the properties/functions of resins, cross-linkers, catalysts, and chemical stoichiometry. The higher the cross-linking density, the higher the hardness, and the better the scratch resistance. However, nanotechnology has paved new pathways for increasing surface hardness.
This concept involves incorporating small amounts of nano-sized aluminum oxide or silica into the coating. Aluminum oxide and silica are minerals with extremely high hardness, with Mohs hardness of 12 and 7-8, respectively. These materials can be used as pre-dispersed additives in liquid form for ease of mixing. Nano-particles existing in the surface layer of the thin film enhance scratch hardness. This can protect the film from damage, friction, abrasion, and minor scratches. Hence, these coatings can maintain gloss for longer periods under actual usage conditions such as in automobiles, wooden furniture, parquet flooring, and UV-cured varnishes, and they are even highly effective in protective layers for mobile phones.
When the particle size is within the conventional micron range, these metal oxides cause light scattering, resulting in opacification of the coating. However, when these particles shrink to the nano-size range of 20-40 nm, they do not scatter light and become as transparent as resin films. The primary contribution of nano-size is transparency to visible light, which helps maintain the transparency of the film.
Although silica is not as hard as alumina, its refractive index is lower, closer to resin, thus better maintaining transparency compared to alumina. However, alumina can be used in lower quantities (1-2%) compared to silica to achieve the same degree of surface hardness. Surface-modified nano-silica can also provide better scratch resistance.
(Further reading:Reduce the material thermal expansion coefficient (Low CTE), solve the warpage problem, the main application description of spherical silica!! ）
Another advantage of this method is that it does not interfere with chemical cross-linking reactions, thus curing speed (and the pot life of 2K systems) is basically unaffected.
We generally offer 30wt% dispersion products with a variety of solvent choices; if you prefer to do dispersion yourself, there are also powder products available to choose from.
#scratchresistant #wearresistant #nanomaterials #nanosilica #nanoalumina #phoneprotector #scratchresistantcoatings #scratchresistantpaint
