The methods can be divided into two categories: physical extinction and chemical extinction.
7.1 Physical extinction
That is, the inorganic packing method is used to reduce the gloss of the film.
However, because the filler is more than 1/4 higher than the resin density, to achieve the destruction of the film smoothness, rough surface effect, the amount of filler is relatively large, the direct consequence will be the leveling of the coating, mechanical properties greatly reduced, so this method can not reduce the luster is very low.
Physical extinction can also be achieved by adding stearate, wax and metal salt complexes, organometallic compounds, and polymers that are incompatible with the system.
7.2 Chemical extinction
The main methods are adding IPN matting agent, using matting curing agent, mixing different resins or curing agents, etc.
However, there are few extinction agents developed for polyurethane system, which are rarely sold in the domestic market. The extinction agents developed by a domestic research institute can produce 5%~9% gloss coating at least. However, the formula cost of this product is too high, and the resulting film has poor smoothness when the gloss is low.
Extinction curing agent is more used in epoxy powder coatings.
Powder coating powder manufacturer to launch an extinction of polyurethane powder paint special curing agent, it is a kind of grafted compounds, works on the one hand, make with hydroxyl polyester and caprolactam closed reaction of isocyanate, on the other hand make certain epoxy groups and hydroxyl or carboxyl reaction on the curing agent, so that the film gloss fell below 30%, even matt coating can be obtained, However, the reproducibility is poor and easy to be affected by factors such as color and filler.
The extinction effect of the method of mixed curing agent is not obvious, and the domestic polyurethane curing agent mainly depends on import, the variety is few, it is difficult to choose the right variety.