Research on the processing technology of ETFE powder coatings

Abstract:
ETFE (Ethylene-Teflon) co-polypluoride powder coatings have an irreplaceable position in the field of corrosion protection because they can be made into seam-resistant chemicals and high temperature-resistant coatings. This paper briefly summarizes the development status of ETF powder coatings at home and abroad, introduces the product brands of major foreign manufacturers, and the ETTE powder coatings of Shandong Huafluoro company. This paper discusses the two coating processes of electrostitial spraying and rolling coating, and analyzes the technical conditions of the process and the key points of particle size and particle size distribution control in powder preparation
China
. The characteristics of ETF's chemical resistance are introduced, and the chemical resistance of Shandong Huaflue's ETFE products and imported ETFE products at different temperatures is compared.
0 Foreword
Ethylene-Teflon (ETFE) co-polypluoride powder coating formed by the coating film has excellent heat resistance, chemical resistance, weather resistance and electromedicine properties, compared with PTFE, FEP and other anti-corrosion lining materials, more balanced performance, good melting processing, good viscosity of the substrate, corrosion resistance is almost no difference.
ETFE relatively high fluorine content (more than 60%) effectively protects the carbon chain skeleton, provides good durability of the coating, the molecular structure of the rule arrangement gives it a certain crystallization, provides barrier for the coating, resists the penetration of acid and alkali, etc., Figure 1 shows the three-dimensional structure schematic of the ETF.
With the growth of the domestic integrated circuit and liquid crystal plant PECVD (plasma-enhanced chemical vapor deposition) industry, the demand for corrosion protection of the etching process exhaust pipe has increased sharply, while the etching gas has strong corrosion and high permeability, PECVD exhaust gas contains flammable and explosive gas silane, which has obviously driven the demand for ETF powder coatings. ETTE powder coatings are also increasingly used in other chemical tanks, pipes, mixing blades, etc. Good meltability makes ETTE powder coatings easy to use electrostitectrical spraying, rotating molding, fluidized bed impregnation into any shape of seam-free anti-corrosion coating film. At present, the domestic research on the synthesis and processing of ETFs has become a hot spot.
1 domestic and foreign
in 1970, DuPont industrial production of ETFs was successful. At present, ETFE production enterprises have the United States Komu, Japan Asahi Nitro, Japan Dajin and the United States 3M and so on. Among them, the United States Como and the United States 3M company most of the ETF products tend to squeeze out the cable, injection molding parts and extruded film, Komu has a small number of powder coatings, Japan Asahi nitro and Dajin mainly produce powder coatings, and has been serialized, foreign ETFE powder coatings major brands and indicators see Table 1 and Table 2. Domestic Shandong Huafluorochemical Co. , Ltd. has built 500t/a production equipment, products covering for electrostature spraying, rolling lining, cable and other powders and grans, products have formed a series, see Tables 3 and 4.
ETFE flame retardant grade conforms to UL94V-0 standard, because of its excellent flame retardant properties and anti-corrosion characteristics, FM mutual insurance company selected to control the spread of fire smoke pipe anti-corrosion lining material, foreign use is huge. Figure 2 shows the factory smoke pipe lined with ETFE resin material.
ETTE powder coating anti-corrosion in a wide range of domestic and foreign applications, such as exhaust gas treatment tower, distillation tower, waste liquid treatment tower, chemical raw material storage tanks, semiconductor manufacturing pipes.
2 Test Part
2.1 Test Equipment
Spray Gun, EPG-3000, Wagner, Germany;
Kodin-6DJ, Jiningko Electric; Laser particle size spreader, GSL-101BI, Liaoning Instrumentation Research Institute; cryogenic shredder, Jiangyin Zhongkai Pharmaceutical Machinery Co., Ltd.
2.2 ETFE electrostectrectrectrative powder spraying technology
The ETFE electrostectrelectrelectrelectrelectrelectrelectrative spraying construction process is shown in Figure 3.
substrate treatment has rust removal, removal of burrs, as well as welding rods to fill gaps, small holes and so on equal treatment. Degreasing is generally made with high temperature, 400 degrees C to maintain 1h, and then according to the thickness of the required coating to choose the size of sand blasting particles, the larger the general thickness, the thicker the sand particles.
in order to fully protect the substrate from corrosion, the film needs to have a certain thickness, generally 100 to 3000 m, in order to achieve sufficient thickness needs to be achieved through multiple spraying.
In order to ensure the formation of a coating surface smoothness is good and easy to live, particle size needs to be less than 150 m, but if the particle size is too small, there will be poor mobility, easy to block the spray gun and low powder rate, therefore, the particle size is less than 30 m part of the mass score should be less than 1%, but also there is too small particle size, then the number of repeated construction, operation becomes cumbersome, and the film repeatedly heated, due to thermal decomposition and the risk of foaming. Shandong Huafluoro Chemical Co. , Ltd. after many tests, in smoothness, reduce the number of construction, increase the powder rate and so on to get the best balance point, the average particle size control between 70 to 120 m, particle shape close to the spherical, construction 4 times can get a total thickness of at least 0.8mm coating film, the construction process smoothly does not block the gun, coating film finish without defects. Figure 4 shows elbow linings and iron plates sprayed with the brand name EC-01ETFE of Shandong Huafluoro chemical co., Ltd.
ETTE electrostectrulation spraying construction is complex, it needs to be sprayed 4 to 5 times to reach the maximum film thickness of 1mm, by adding carbon fiber, fiberglass, etc. to increase the thickness and reduce the shrinkage when curing.
ETFE special-shaped parts spraying, no seams, high adhesion, good bonding durability, add carbon fiber by 5 to 7 spray film thickness of up to 1mm.
In the case of particularly high demand adhesion, can increase the primer, it is reported that the current imported primer generally choose ordinary modified ETFE and polyimide resin or epoxy resin and other composite use to improve adhesion, composite resin should choose melting point or Vika softening point temperature, heat resistance and other melting processing conditions and ETF matching powder resin.
2.3 ETFE rolling coating processing technology
roll coating lining is characterized only for the shape of the more irregular inner surface, film thickness of up to 2 to 5mm, suitable for heavy corrosion, can more effectively prevent the penetration of corrosive liquids and gases.
the basic process of rolling the ETF is shown in Figure 5.
Because the coating is mainly indirectly transmitted heat from the outside through the work piece, and the powder coating is thicker, in order to help heat transmission, the accumulation density is large, the particle size is large, the particle shape is similar to spherical, the particle size is less than 30 m part less than 1%, so that the powder fluidity is good, the particle size is too large to indicate the smoothness of the molding material is not good, so preferably particle size 150 to 300 m. In addition, ETFE powder melting completely depends on the rotation of its own mass in the work piece internal surface even leveling, so the melting index needs to be as large as possible, but the melting index is too large and will be due to the molecular mass decline resulting in reduced performance, so preferably melt index 15 to 35g/10min. Warm-up, melting, cooling temperature and time conditions vary depending on the choice of processing components, furnaces and cooling conditions. For processing lining thicknesses of 2.3mm, the selection conditions are as follows:
warm-up: 250C, 5min;
the melting temperature can vary within a certain range, for example, slightly increase the temperature, can shorten the time, reduce the temperature needs to be appropriately extended time. Table 5 shows the temperature and time conditions for rolling coating.
the spindle and subaxial speed used for ROTAT rotary molding is the same as that used for other conventional polymer rotary molding. Box components, twigs, cylindrical tube parts, expansion sections, etc. use spindle 8r/min, sub-axis 9r/min, sphere or spheroid using spindle 8r/min, sub-axis 10r/min. Using the above rotation conditions, the powder can be dispersed evenly and melted into a lining of equal thickness.
Shandong Huafluorochemical Co., Ltd.'s ETTE powder coating by rotating molding in the distillation tower section surface lining anti-corrosion layer, through the thickness test thickness ≥2.5mm, through the electric spark detector test no pinhole defects, and adhesion and surface finish excellent, has been in normal operation of the device to play an anti-corrosion role, the use of two months without damage. Figure 6 is the anti-corrosion lining of Shandong Huafluoro chemical co., Ltd. rolling-coated distilled tata section, and Figure 7 is the roll-molded seal head of Shandong Huafluoro chemical industry Co., Ltd.
3 ETFE anticorrosity features
ETFE is inert to most chemical media, and Table 6 shows the effects of several common chemicals on ETFE stretching performance. As can be seen from Table 6, ETFE is well resistant to inorganic acids, alkalis and organic solvents. In addition to strong oxidizing acids, such as strong nitric acid, organic amines, sulfonates, etc. at high temperatures or near boiling point temperatures can lead to the destruction of the ETF coating. Table 6 is the data of an imported ETFE and Shandong Huafluoro chemical company ETFE into a 1mm thick micro-dumbbell sample test, in which the fracture elongation rate changes by less than 15%, does not affect normal use.
4 Conclusion
In addition to electrostectrectral spraying and rolling coating, it is also possible to form a seam-free coating film on the surface of the work piece by fluidized bed impregnation, but it is rarely used at present. The market is widely used in Dajin, Asahi nitro and Komu ETTE powder coating, coating process is generally electrostitectrical spraying and rolling coating method. Domestic ETFE has several are being tested in the market, but most of the existence of cracking phenomenon, impurities, poor processing, durability and corrosion resistance is insufficient, some use for a period of time cracking, and surface finish, texture and imported products there is a certain gap. Shandong Huafluoroelastic Co., Ltd.'s products have excellent corrosion resistance, showing the same high temperature corrosion resistance as imported products.
because of the poor dispersion of ETF resin pigments, most of the ETF powder coatings are colorless and poorly covered after melting into a film. In addition, the addition of primers can improve adhesion, but there is no research, patents or products in this area reported. This is also an area where researchers will need to continue their efforts in the future. In addition, domestic ETTE powder coatings also need to pass FM certification to be approved by Huawei, Samsung, TCL and other end customers.
with the continuous deepening of domestic research work, domestic ETFEs will certainly catch up with the level of developed countries, and form their own characteristics. Shandong Huafluor chemical co., Ltd. is still continuously improving and research and development of new ETTE powder coatings, and continuously improve processing and use performance, while further expanding its use.
Wen/Yu Meixiang, Guo Xigang, Wang Yanping and Shandong Huafluoroelastics Co., Ltd.
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