The improvement of the performance of powder coatings by pretreating composite raw materials

Since the 80s of the 20th century, powder coatings have been increasingly recognized by the coating and coating industry as a kind of environmentally friendly coatings. Especially in recent years, the demand for environmental protection and sustainable development has risen rapidly. Whether from government regulations or industry trends, low volatile and non-volatile coatings will become the main direction of the overall development of the coating industry. However, with years of development, many disadvantages of powder coating have always plagued practitioners, the most important of which is the dispersion of materials. Dispersion is an ever-familiar problem in the coatings industry, and powder coatings have poor material dispersion. The main reason is that there is no solvent in the coating, and the extrusion mixing and dispersion is carried out under molten conditions and in a short time. The particle size, viscosity, absorption and other indexes between materials are very different, and it is difficult to achieve adequate wetting, coating and mutual miscibility. Although great improvements have been made in terms of process and system viscosity, there is not much improvement in coating performance. In recent years, some pretreatment composites have appeared, pointing to another way out in this regard, making there are more options for improving the performance of coatings.

Application of surface coating technology

Such raw materials are more common, such as the coating of metal powders, pigments, fillers, etc., and the selection of different coating materials can bring better performance. The outer layer of aluminum powder coated with silica or acrylic acid can effectively improve its oxidation resistance, and the outdoor use of aluminum powder is possible under the multi-layer coating. The latest polyester-coated aluminum powder relies on the outer coating to be more similar to the primer, and avoids the shortcomings of large oil absorption and the difference between the charged and the primer. In the case of only using post-mixing, the amount is increased, and there is no separation between the metal powder and the base powder, and the metal powder effect is good. At the same time, the flash point of aluminum powder after multi-layer coating has also been reduced accordingly, so that the safety of its use has been improved. By coating different organic materials on the surface of the filler, the functional filler can effectively reduce the oil absorption of the filler and adjust the leveling and gloss of the coating after use. The pearlescent coated with stearic acid can get a better shimmering effect in the coating and reduce its dosage. The calcium carbonate coated with different organic compounds also greatly improves the surface state on the premise of improving its stability, and has been applied in many fields. The dispersion of pigments has always been the most important process in the coatings industry. How to effectively destroy the agglomeration between small particles of pigments and make them stably dispersed in the coating system is also the focus of research by pigment and equipment manufacturers. Powder coatings are very different from other types of coatings in this respect, with overly simplistic processes and very large viscosities that make pigment dispersion more macroscopic.

The role of functional material structures

The core of the pearl determines the degree of its scintillation, and there are natural silicon to artificial silicon and then glass pearl, and we can get different changes. Similarly, a change in particle size can improve the dry powder flow of the powder while providing the material function. These are some of the effective applications of physical states in powders. When making high-hardness products, we generally choose two ways: surface hardening and physical hardening. The most common in physical hardening is silicon, and the Mohs hardness of quartz can reach 7.5, but we ignore another high hardness substance, that is, corundum with a hardness of 9 on the Mohs scale, and China's corundum reserves are very large. The main component of corundum is A1203, from the white corundum used in aluminum smelting to the most slag black corundum, and how to effectively improve the dispersion of corundum in the coating is the key to its application. High-temperature calcination of alumina monohydrate with a particle size of less than 5 microns can obtain corundum particles with a porous structure. On the premise of increasing the specific surface area of the particles, the adhesion between the particles and the resin can be improved. The use of a slightly lower viscosity curing system allows for more thorough wetting of the system. When the addition amount of this kind of hardening seasoning reaches 40%, the surface pencil hardness of 5H-6H0 is determined according to the wear resistance of GB/T 1768-2006 paint film, 1kg positive pressure, and the mass loss of 10,000 cycles can be controlled between 100~200mg.