In order to study the manufacture of low-temperature curing epoxy powder coatings, the powder coating coating temperature can be lowered so that it can be coated on the surface of heat-sensitive materials. The selection of synthetic resins, curing agents, pigments, fillers, and additives was discussed, and the formula composition was screened by experiments.
The formula of low-temperature curing epoxy powder coating was determined, the process route was determined, and its performance was analyzed and tested. The results show that the curing temperature of low-temperature curing epoxy powder coatings can be reduced to 110 ℃. It is possible to paint powder coating on the surface of heat-sensitive materials.
Powder coatings and coatings are favored by people because of their resource-saving, energy-saving, pollution-free, high-efficiency, and easy-to-realize automated production advantages. The output has grown rapidly and has become one of the development directions of the coating industry.
The curing conditions of general powder coatings are mostly at a temperature of 150 to 180 ℃, and some are as high as 200 ℃, and the time is 20 to 30 minutes. There are disadvantages of higher baking temperature and longer time.
The higher baking temperature brings considerable difficulties to the coating of non-heat-resistant substrates such as plastics, wood, and solder metal parts, which restricts the expansion of the application range of powder coatings. The baking time is long, the production cycle of the product is long, and the production efficiency is low.
How to effectively reduce the curing temperature and curing time of powder coatings has always been a concern in the powder coating industry. From the perspective of energy saving, cost reduction, efficiency improvement, and expansion of the application range of powder coatings, the development of low-temperature curing powder coatings is of great significance.
The low temperature curing of powder coatings is achieved by increasing the reactivity of the resin and the curing agent. In this experiment, suitable accelerators were selected to realize the low-temperature curing of powder coatings.
Epoxy resins have reactive epoxy groups, and the reactivity of the groups varies with the molecular weight of the resin and the structure of the resin. The resin for powder coatings has the following characteristics: the molecular weight of the resin is small, but the glass transition temperature is higher than 50 ℃, the resin is brittle, it is easy to be mechanically crushed to obtain the required particle size at room temperature, and the powder is not easy to agglomerate at room temperature. The resin has a low melt viscosity at the curing temperature of the powder coating, and is easy to level to obtain a relatively thin and smooth coating film. There are many kinds of resins. By mixing resins with different melting points, viscosity and epoxy value, the resins with the required technical indicators can be adjusted and made into powder coatings with different needs.