The formula of Powder coating is mainly as follows: resin and its curing agent, which is the basis of coating film formation; Additives to improve the appearance or performance of the coating; Pigment to give the coating covering and color; The filler mainly plays the role of physical enhancement.
When the commonly used saturated polyester resin, epoxy resin and other materials are above 350 ℃, the carbon oxygen bond will soon break and decompose, which is manifested in the powdering and falling off of the coating. Silicone resin is the first choice for the main resin of high temperature resistant Powder coating because it takes silicone oxygen bond as the main chain and gives silicone resin high oxidation stability due to its high bond energy.
Pigments and fillers are the key to affect the performance of high-temperature resistant coatings. Fillers should have high stability and can react with siloxane functional groups of silicone resin. Therefore, silicate fillers are the first choice, such as mica powder, silicon micro powder, etc. In addition, silicate materials, mainly because their phosphate can react with the metal, so as to ensure the adhesion between the coating and the substrate. In terms of pigments, most conventional pigments can not withstand high temperatures above 500 ℃. Titanium dioxide can be selected for white, iron oxide black, iron manganese black, red, yellow and blue can be selected for black. It is recommended to select wrapped products, and the overall formula will ensure that heavy metals will not exceed the standard.
Production process control of high temperature resistant Powder coating
The production process of high temperature resistant Powder coating is not different from that of ordinary products. The production process is shown in the table below. The process parameters need to be controlled mainly in the melt extrusion stage. Due to the low softening point of silicone resin, it is necessary to control the appropriate extruder temperature to ensure the mixing uniformity in the melt extrusion stage. In the crushing stage, it is necessary to ensure that the particle size division is as narrow as possible, because the coating of high-temperature resistant Powder coating will expand when heated. The better the uniformity of the coating, the lower the possibility of damage caused by expansion.
As a functional coating, high temperature resistant Powder coating mainly focuses on its high temperature resistance performance. The high temperature resistance performance is tested in two ways. One is to determine the temperature test, and use muffle furnace to test the plate surface effect and adhesion after the test plate is baked at a certain temperature for a certain period of time. The second is the practical application test. The coating is applied to the applied workpiece and tested for a certain time in the actual application environment.
Barbecue ovens, braziers and other products, on the one hand, require the coating to have temperature resistance, on the other hand, they also need to have sufficient anti-corrosion effect. After all, consumers do not want to see rust when using. Therefore, the salt spray resistance of high temperature resistant Powder coating is also a key index. In this paper, the effects of the amount of zinc phosphate of different antirust materials on the salt spray resistance of and high temperature resistant Powder coatings are compared. The formula is shown in the table below.