Commonly used matting agents are wax matting agent, non-wax matting agent and matting curing agent.
Wax type matting agent is non-reactive, mainly through the miscibility with the film-forming material and other physical effects to produce matting.
Extinction curing agent extinction principle is the use of powder coating formula in two different reaction activity curing agent, a reaction activity is large, fast reaction speed. The other reaction activity is low, the reaction speed is slow, due to the difference in reaction speed and compatibility between the reaction products, resulting in a microscopic rough surface, diffuse reflection of light and achieve extinction.
By adjusting the amount of resin and matting curing agent, it is possible to control the gloss of the coating film, which is more convenient to use.
Because of the organic solvents, film-forming shrinkage, matting is easy, although due to the different resin systems and film thickness of such coatings, the use of matting agents also differ. But the generality is large, mainly to adjust the amount of matting agent and particle size on. Synthetic silica gel with high pore volume is the most effective. In order to prevent the matting agent in the varnish precipitation, wax treatment of silica matting agent is preferred.
Water-based coatings rarely use volatile organic solvents. Drying hydrated silica is not very suitable, because micron-level synthetic silica matting agent is porous material, strong water absorption capacity, poor stability of the base material particles, easy to make the quality of the coating film deterioration. syloid W300, W500, W900 type matting agent of Grace is a hydrogel type silica matting agent, water content of 55%, dry pore volume of 1.2mL/g. Appearance Still liquid white powder. Easy to add, strong wettability, easy dispersion, no water absorption, no bubble generation, particle size release after drying is unchanged. Although the pore volume of W-type matting agent is small, it is a more ideal matting agent for water-based coatings because volatilization will shrink the surface of the coating film when drying, and matting is relatively easy.
When the solid content of the coating exceeds 70%, it is difficult to mattify. For high solids alkyd coatings and polyurethane coatings matting, crude silica matting agent is the most effective. And to a higher dosage.
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