Coating knowledge: selection of epoxy resin for insulating powder coating of electromagnetic wire

Core tip: in the 21st century, powder coating has become the mainstream of green coating with its advantages of environmental protection, cleaning, zero VOC release, easy assembly line operation, high efficiency and high performance Powder coating plays a more and more important role in the insulating materials used in electronics and motors The products are widely used in various fields such as motors, electronics, high-voltage electrical appliances, automobile industry, aviation machinery, etc However, insulating powder coating is still in its infancy in the field of electromagnetic wire coating, which shows that there are not many brands of products, and the overall performance of insulating powder coating is very different from that of solvent coating represented by polyimide, which restricts the insulating powder to a large extent Application scope and advantages of roller ceramic coating Recommended introduction: the surface of ceramic rubber plate used for roller ceramic coating is cast into durable rubber plate by hundreds of independent small ceramic pieces Each ceramic piece has raised characteristics Under general conveyor belt pressure, thousands of unique cast bumps can produce positive traction, prevent slipping and extend the service life of conveyor belt roller At the same time, the bottom layer adopts high-quality rubber, which has strong elasticity and can play a good impact resistance role The scope of application of roller ceramic coating is one three six 83857180 (the same as V) 1 Roller coating in extremely harsh working environment 2 The belt joint is not suitable for fixing with iron buckle; 3 It is suitable for leather Home of coatings: in the 21st century, powder coating has become the mainstream of green coating with its advantages of environmental protection, cleaning, zero VOC release, easy assembly line operation, high efficiency and high performance Powder coating plays a more and more important role in the insulating materials used in electronics and motors The products are widely used in various fields such as motors, electronics, high-voltage electrical appliances, automobile industry, aviation machinery, etc However, the insulating powder coating is still in the initial stage in the field of electromagnetic wire coating, which shows that there are not many product brands and the overall performance is far behind the solvent coating represented by polyimide, which to a large extent restricts the market promotion and application of insulating powder coating in this field In this paper, the insulating powder coating for electromagnetic wire (aluminum wire) coating which is currently used in the field of electrical machinery is studied The pure epoxy insulating powder coating product is prepared The softening and breakdown temperature can reach more than 150 ℃, which can partially replace the solvent insulating coating As we all know, pure epoxy powder coating has excellent insulation and corrosion resistance, which is closely related to the molecular chain structure of epoxy resin The hydroxyl group in epoxy resin has high polarity, which can form chemical bond with metal surface, so that the adhesion of the resin is excellent; the ether bond in molecular structure provides excellent chemical resistance and corrosion resistance, and its bending is also good; the propane group and benzene core give the epoxy resin heat resistance and Mechanical rigidity; Among them, epoxy group and hydroxyl group have reactivity, which can be cross-linked into a network structure when reacting with specific compounds At present, there are two main types of epoxy resin for powder coating in the market: bisphenol a type and o-cresol type Bisphenol a type epoxy resin, especially E-12 type, is widely used in the field of powder coating, with excellent comprehensive performance However, the epoxy functional groups in the sub chain of bisphenol a type epoxy resin are generally two, and the crosslinking density formed after crosslinking with curing agent However, o-cresol epoxy resin can have many epoxy functional groups, which can form a large cross-linking density after participating in the reaction, thus improving the heat resistance of the film, but also damaging the toughness of the coating to a certain extent The insulating powder coating for electromagnetic wire is different from the powder coating for motor stator and rotor It requires the coating to have excellent flexibility as well as insulation performance (Electrical and thermal properties) During the test, the bisphenol-A epoxy resin with epoxy equivalent of 700-900, the o-cresol-a epoxy resin with epoxy equivalent of 200-300 and the o-cresol-b epoxy resin with epoxy equivalent of 800-900 were used, the micronized dicyandiamide was used as curing agent, the 2-methyl-imidazole (2mi) was used as curing promoter, and the general leveling agent, benzoin, degassing agent and pigment were selected The effect of different types of epoxy resin on the properties of the coating film was compared The effect of epoxy resin type on the properties of powder coating O-cresol-a epoxy resin is too rigid and has poor compatibility with bisphenol-A epoxy resin Although it can greatly improve the heat resistance (softening and breakdown temperature) of the coating, it also seriously damages the flexibility of the coating Therefore, it is not suitable to be used as an insulating powder coating formula with high toughness requirements such as electromagnetic wire Epoxy resin B is a kind of phenolic resin with three functions Its rigidity is relatively small compared with epoxy resin A, but its toughness increases With the decrease of its addition, the coating toughness increases and the softening and breakdown temperature decreases When the ratio of epoxy resin 150 (bisphenol A) / 50, it can meet the toughness requirements of the coating film At this time, the softening and breakdown temperature rises to 142 C Therefore, in this study, bisphenol A epoxy resin E-12 and o-cresol epoxy resin B (E-12 / epoxy resin B = 150 / 50) were chosen as the resin system [focus on WeChat official account "paint net"; 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