Electrostatic spraying is liquid spraying, also known as fluorocarbon spraying, and it is called curium oil in Hong Kong. High-grade spraying is more expensive and has been used abroad for a long time. In the past two years, aluminum panel curtain walls have been widely used in China. Due to its excellent characteristics, it has been increasingly valued and favored by the construction industry and users. Fluorocarbon spray coating has excellent resistance to fading, blooming, corrosion resistance from atmospheric pollution (acid rain, etc.), strong UV resistance, strong crack resistance and the ability to withstand harsh weather environments. It is beyond the reach of ordinary paints.
1. Fluorocarbon spray raw materials and structure
Fluorocarbon spray paint is based on polyvinylidene fluoride resin nCH2CF2 baked (CH2CF2)n (PVDF) as the base material or with metal Aluminum powder is a paint made of pigments. The chemical structure of fluorocarbon base material is combined with fluorine/carbon bonds. The combination of this short-bond structure with hydrogen ions is considered the most stable and strongest combination. The stability and firmness of the chemical structure make the physical properties of fluorocarbon coatings different from ordinary coatings. In addition to its excellent wear resistance and impact resistance in terms of mechanical properties, it also shows long-term fading resistance and UV resistance, especially in harsh climates and environments. It began to be used in engineering plastics in the early 1960s for wires and cables. In 1965, the American Pennwalt Chemical Company first synthesized polyvinylidene fluoride as a base material and metal particles and aluminum powder into a building finish, also known as metallic paint. Trademarked under Kynar 500. Since then, manufacturers around the world have begun to use Kynar 500 to produce their own fluorocarbon coating topcoats to meet the needs of coating indoor and outdoor aluminum materials in high-end buildings. Its wide range of color choices, beautiful and solemn appearance, and durability have attracted many customers around the world. The grand curtain wall architecture adds to the splendor. Paint manufacturers' guarantees on the service life of coatings began with 10 years, 15 years, and have evolved to 20 years.
American research institutions have conducted tests and comparisons on fluorocarbon coatings, super coatings, and general coatings. Samples of the respective coatings were exposed to the scorching sunshine in Florida, USA, and exposed to the harsh conditions of humid and salty air. After being exposed to the environment for 12 years, it has been actually proven that the stability and durability of fluorocarbon coatings are 30 and 80 percentage points higher than the other two coatings. The fluorocarbon coatings ensure use in various harsh environments.
Many fluorocarbon paint manufacturers around the world generally use Kynar 500 or Hylar 5000 as the base material of neon carbon paint. There are no officially certified manufacturers in China. The main manufacturers that produce fluorocarbon coatings are:
1. British 1CI Company; 2. American PPG Company; 3. American Valspar Company; 4. DNT Singapore (Dainippon Paint Singapore Company); 5. Japan Kawsai (Kansai) Paint Company; 6. Korea chemical company; 7. Taiwan Fengyuan Paint Co., Ltd.;
2. Fluorocarbon spraying technical requirements and standards
Fluorocarbon spraying is a high-end surface coating process, and the quality requirements of the entire process are extremely strict. In addition to the fact that fluorocarbon paint manufacturers need to obtain a quality license to produce Kynar 500-based fluorocarbon paint, the entire surface treatment process of the paint manufacturer, including the pre-treatment process, spraying process and curing process, needs to have strict quality control. , to ensure the quality of aluminum coating. In the fluorocarbon spraying industry, the American Building Manufacturing Association standard AAMA-605.02.90 is currently the main basis. This spraying standard is recognized as the main international standard for inspecting coating quality. The following are the main indicators related to fluorocarbon spraying in the AAMA-605.02.90 standard.
In the AAMA standards, South Florida in the United States is mentioned in many places as the testing standard because the climate there is famous for its humidity, high temperature, and direct sunlight, so it is considered to be for coating quality inspection. Harsh environment.
There are also some inspection standards in the world that are similar to the American AAMA-605.02.90 standard, which are also used to judge the quality of fluorocarbon spraying.
They are:
1. British BS6496-1984 standard construction aluminum alloy profiles and coating standards for plates.
2. German GSBRAL-RC 631 1994 standard construction aluminum quality inspection standard.
3. Australian AS3715-1989 standard metal coating standard.
4． South Africa SABS-1993 Standard for exterior aluminum coating of buildings.
5． The Swiss construction industry uses the aluminum coating standard 1994.
American Building Manufacturing Association Standard (Extract) AAMA-605.02.90
3. Fluorocarbon spraying equipment and process
Fluorocarbon coating itself Determined by performance, spraying equipment must ensure excellent atomization effect and ensure the uniformity of the spray coating. The distribution of metal particles in fluorocarbon coatings directly affects the appearance of the coating. The coating is uniform and the excellent quality fluorocarbon coating has metallic luster, bright color and obvious three-dimensional effect. However, fluorocarbon spray coatings using inappropriate spray equipment will produce uneven colors, shadows on the surface, or weak coatings. It greatly affects the decorative effect of fluorocarbon. In order to achieve good spraying effect, high-voltage electrostatic electric spray gun is used. The United States, Japan, Germany and other countries produce various types of spray guns of various brands. Each has its own characteristics.
The fluorocarbon spraying process mostly uses multi-layer spraying to give full play to the durability and weather resistance of Kynar 500 metallic paint. Strict quality control is required from the front surface treatment of the aluminum to each spraying process. The final product must meet the American Architectural Manufacturing Association AAMA-605.02.90 standard.
The fluorocarbon spraying process is:
Pre-treatment process: degreasing and decontamination of aluminum → water washing → alkali washing (degreasing) → water washing → pickling → water washing → chromization →Water washing→Pure water washing
Spraying process: spray primer → topcoat → varnish → bake (180-250℃) → quality inspection
Multi-layer spraying process is carried out three times Spray (referred to as three-spray), spray primer, topcoat and varnish and secondary spray (primer, topcoat).
1. The purpose of pre-treatment: before spraying aluminum alloy profiles and plates, the surface of the workpiece must be degreased, decontaminated and chemically treated to produce a chromium film, increase the bonding force and anti-oxidation ability of the coating and the metal surface, and facilitate the extension of the paint. The service life of the membrane.
2． Primer coating: As a primer coating to seal the substrate, its function is to improve the anti-penetration ability of the coating, enhance the protection of the substrate, stabilize the metal surface layer, strengthen the adhesion between the topcoat and the metal surface, and ensure the surface finish. The color uniformity of the paint coating, the thickness of the paint layer is generally 5-10 microns.
3. Topcoat coating: The topcoat coating is a key layer of the spray coating. It provides the decorative color required for the aluminum material, makes the appearance of the aluminum material meet the design requirements, and protects the metal surface from the erosion of the external environment, acid rain, and pollution. , to prevent ultraviolet rays from penetrating. Greatly enhances the anti-aging ability. The topcoat coating is the thickest paint layer in spraying. The thickness of the paint layer is generally 23-30 microns.
4． Varnish coating: The varnish coating is also called varnish coating. Its main purpose is to more effectively enhance the resistance of the paint layer to external erosion, protect the topcoat coating, increase the metallic luster of the topcoat color, and make the appearance more vivid. Glossy and dazzling, the coating thickness is generally 5-10 microns. The total thickness of the three spray coatings is generally 40-60 microns, and can be thickened if required.
5． Curing treatment: The three-spray coating generally requires secondary curing. The aluminum material enters the curing furnace for processing. The curing temperature is generally between 180°C and 250°C, and the curing time is 15-25 minutes. Different fluorocarbon coating manufacturers will base their requirements on coating, providing optimal temperature and time. Some chlorine carbon spraying factories (curium oil factories) also changed the two curings during three sprays to one curing based on their own experience.
6． Quality inspection: Quality inspection shall be in accordance with AAMA-605.02.90 standard.