Selection of epoxy resin for insulating powder coa

Selection of epoxy resin for insulating powder coatings for electromagnetic wires

since the beginning of the 21st century, powder coatings have become the mainstream of green coatings together with water-based coatings because of their advantages of environmental protection, cleanliness, zero VOC release, easy assembly line operation, high efficiency and high performance. Powder coating plays a more and more important role in the insulation materials for electronics and motors. Products are widely used in various fields such as motors, electronics, high-voltage electrical appliances, automotive industry, aviation machinery and so on. However, the insulating powder coating is still in its infancy in the field of electromagnetic wire coating, which shows that there are few product brands and there is a big gap between the overall performance and the solvent based coating represented by polyimide, which restricts the market promotion and application of insulating powder coating in this field to a great extent

this paper mainly studies the insulating powder coating for electromagnetic wire (aluminum wire) coating, which is currently used in the field of motor. The pure epoxy insulating powder coating product is prepared, and the softening and breakdown temperature can reach more than 150 ℃, which can realize the partial replacement of solvent based insulating coating

as we all know, pure epoxy powder coating can produce lighter pallets at a faster speed and then stop data processing. It 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 bonds with the metal surface, so that the adhesion of the resin is particularly good; The ether bond in the molecular structure provides excellent chemical resistance and corrosion resistance, and its bending property is also very good; Propane group and benzene core endow epoxy resin with heat resistance and mechanical rigidity; Among them, epoxy group and hydroxyl group have reactivity, which can be crosslinked into a like structure by reacting with specific compounds

at present, the epoxy resins commonly used in the market for powder coatings mainly include bisphenol A and o-cresol. Bisphenol A epoxy resins, especially E-12 bisphenol A epoxy resins, are more widely used in the field of powder coatings, with excellent comprehensive performance, but there are generally two epoxy functional groups in the molecular chain of bisphenol a epoxy resins, and the crosslinking density formed after crosslinking reaction with curing agent is limited, The o-cresol epoxy resin can have multiple epoxy functional groups, which can form a large cross-linking density after participating in the reaction, so as to improve the heat resistance of the coating, but also damage 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 that the coating film not only have insulating properties (Electrical and thermal properties), but also have excellent flexibility

during the test, bisphenol A epoxy resin with epoxy equivalent of 700 ~ 900, o-cresol epoxy resin with epoxy equivalent of 200 ~ 300 and o-cresol epoxy resin with epoxy equivalent of 800 ~ 900 were used, micronized dicyandiamide was used as curing agent, 2-methyl-imidazole (2mi) was used as curing accelerator, general leveling agent, benzoin, degassing agent and pigment were selected, and no filler was added, The effects of different epoxy resin types on the film properties were compared

the data shows that o-cresol epoxy resin A is too rigid and has poor compatibility with bisphenol A epoxy resin. Although it can greatly improve the heat resistance of the coating (softening and breakdown temperature), it also seriously damages the flexibility of the coating, so it is not suitable to be used in the insulation powder coating formula with high toughness requirements such as electromagnetic wires

epoxy resin B is a trifunctional novolac epoxy resin. Its rigidity is relatively small compared with epoxy resin A, but its toughness increases. With the decrease of its addition, the toughness of the coating increases and the softening breakdown temperature decreases. With the ratio of bisphenol A epoxy resin 150 (bisphenol A)/50, it can meet the toughness requirements of the coating. At this time, the breakdown temperature of softening and developing rail welding material processing technology rises to 142 ℃. Therefore, in this study, it is decided to adopt the resin system with bisphenol A epoxy resin E-12 and o-cresol epoxy resin B (e-12/epoxy resin b=150/50) as the formula

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