Epoxy powder coating

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powder coating is a technical product used to decorate metal material substrates and form protective filmsIts advantage is that the liquid powder is suitable for dry coating, suitable for heating to form a continuous, economical filmIt also provides some value in terms of safety and healthIt is characterized by a more uniformtechnology membrane, resulting in more consistency in performanceGood process technology and chemical resistanceeconomy that does not consume solvents and does not require energy and space for flashingUsually applied once, highly automated, with very high efficiency, materials can be recycled in a fairly simple waysafety and health without releasing solvents that pollute the air, reduce the risk of fire or explosion, and work in clean environmentsfirst as a powder organic coating is based on thermoplastic polymers, and later the development of technology extended to thermoset polymer powder coatings, more famous is epoxy resinThe epoxy preparation powder coating has a considerable range of development, suitable for application in various technical and economic sectors, because epoxy resin/ curing agent system can obtain the following properties:curing addition action without volatile spout;they also have some drawbacks:precise tinting is more difficult than liquid pigments, changing colors in the production line is more difficult, and more systems require relatively high oven temperaturesBecause epoxy powder coatings have many good properties, they are used for a wide range of purposes:and school facilities, refrigerators and freezers, washing machines, radios, lampshades, bicycles and motor vehicle racks, car drives, components and bodies, agricultural machinery, and external coatings for pipelines the development of epoxy powder coatings to meet the diverse needs of the industrial sector, new coating preparation techniques, new powder preparation methods and new application techniques, all of which are completely different from liquid coatings the basic requirements of the mixture that make up epoxy resins, curing agents, pigments and additives, and in the preparation of powder coatings, some effect on the physical and chemical properties of the mixture is applied First, the resin system must have the ability to immerse pigments and fillers, allowing for minimal reaction between the resin and the curing agent under temperature and time conditioning Products of uniform quality must be relatively easy to produce powders that require particle size; Static electricity is most commonly used, so powder particles must have the ability to be charged When heated, the powder must melt and flow into a smooth continuous film Wet substrates, cured under baking, and the resulting coating in this production process has the required mechanical resistance in order to meet these performance requirements, the mixture system requires a suitable melting range and melting viscosity, and in the addition system of these resin reinforcers, there must be a suitable range of activity, using the appropriate temperature in each sequence of powder preparation, storage and output, curing baking phase, etc In order for the user to obtain different requirements of powder coatings, this can consist of different epoxy resin/ curing agent/additive systems the molecular weight, epoxy content and softening point range of epoxy epoxy resin softened the main effect on some properties of powder coatings Most generally speaking, the role of molecular weight and softening point growth can be summarized as follows: performance resin molecule increases the role of pigment dispersion is difficult
requires high temperature
storage stability membrane fluidity is reduced
mechanical properties - flexibility / impact-resistant improvement - viscosity due to reduced substrate wetting and reduced - hardness is not affected
the best balance of chemical resistance is small
the best balance should include physical storage stability (i.e., resistant to bonding or clumps), when the epoxy content of the resin is 1000-1400mmol/kg, the membrane fluidity and mechanical properties are improved Solid resins of low and high molecular weight can be used to regulate special properties in special compositions additivesome some powder coating composition need to add flow control agent, which is the leveling agent The amount of the dosage is generally 1-10% of the amount of resin Leveling agents can be added immediately after the preparation of epoxy resins, to make epoxy resins containing leveling agents such as Epikote3003-4F-1, 3003-4F-2, 3003-4F-10, they contain Acronal4F amount of 1, 2, 10% It is also possible to add a certain amount of leveling agent to the product's liquidity requirements when preparing powder coatings curing agent is an essential part of the resin mixture system and has a decisive effect on the performance of powder coatings One of the obvious requirements is the activity of their resin/curing agent systems, which should be very low at normal transport and storage temperatures and high at industrial actual baking temperatures In the powder preparation process should make it stable in order to mix, curing agent at room temperature should be solid The number of curing agents is related to the different requirements of the type and the chemical reaction of the base resin and the cross-linking density of the final film Therefore, different levels of curing agent can be used for product powders with different curing agent ratios The balance between different humidity and various properties, such as price, chemical resistance, mechanical properties, over-baking performance and color retention, is different from a wide range of requirements for industrial users Many types of commonly used curing agents are generally based on the user's conditions of use, product quality requirements, equipment environmental conditions and other conditions through testing to establish pigments and fillers are commonly used in powder coatings First they must be dry, because moisture reduces its leveling and causes the film appearance of the pinhole, second, it must have sufficient heat resistance in order to withstand the expected baking system, third it must be resistant to the chemical properties of the curing agent, and does not interfere with the curing reaction adding the amount of pigment in the powder coating will reduce the flexibility of the membrane, as evidenced by impact strength data, the cone shaft bending and slow penetration test decline The pigment precipitation value level becomes a very important relationship at this time, which is related to the particle size and packaging characteristics of the filler There are two methods for preparation of industrialization: Z-leaf mixing and extruder mixing Their advantages and disadvantages are compared as follows: method advantages and disadvantages note
Z-leaf plate mixing method excellent dispersion in the melting humidity long-term retention in 1 processing slow-curing powder
color regulation easy batch discharge needs to increase the temperature
mixing operation is simple not suitable for fast curing system batch process is now mostly replaced by extrusion method can mix liquid mixtures in the ingredients can remove any humidity long-term cleaning material loss relatively high squeezer mixvery very good mixing investment high applicability
continuous production requires skilled operation
material loss low components need to be initially mixed
at the melting point melting temperature retention time short color adjustment difficulties
Z-leaf plate mixing large Z-leaf plate mixing requirements with heating temperature of up to 180 degrees C capacity, as well as on the road installed an amperization meter to check the shear load The resin melts and adds pigments and fillers at 130-140 degrees C; Add the leveling agent and completely disperse; finally the reinforcement and the touch changer Heat a well-flowed uniform melt, place it in a pan, cool to room temperature, and then crush, grind, and sift the product For different components shearing and dispersion time may change, allowing each component to have the best dispersion, but this mixed yield is low, only a limited curing agent can be used, and the material heating time is generally not used this method The main requirements of the extruder hybrid extruder make the thermoset mixture continuously and completely displaced, and the material is fully exchanged in a relatively short period of time in heating conditions; In addition, different areas are required to have good temperature control, feeding area and screw cooling is simple, in order to clean the barrel body easy to remove, as well as excellent dispersion The process is as follows: resin, crushing, pigment, filler mixing final reinforcement mixture, extrusion, ribbon cooler cooling, grinder coarse grinding, fine grinder grinding, sieve, packaging powder particle size according to different application methods to control: application method particle size micron electrostatic spray1 00
fluidized bed or flocspray 300 static current bed 100 electrostatic spray voltage is 30-80KV, the coating object does not preheat, the curing layer is about 30-60 microns
fluidized bed or flocspray coating object needs to be warmed up powder coatings are formulated in many places, such as general-purpose, fine-art, anti-corrosion, insulated, flame retardant and so on Is the factory in accordance with the requirements of the user developed a special formula, has its own technical characteristics and application skills