Research On The Organic-inorganic Compound And Extra-thick Insulation Coating For Non-oriented Silicon Steel

In order to reduce eddy current losses during alternatingmagnetization and improve magnetism through reducing iron loss,non-oriented silicon steel, which is used widely in electromechanicalmanufacture, will be coated with a layer of insulating coating. With thedevelopment of times, the demand for motor especially the large-scalemotor is increasing. The larger capacity of motor requires the betterinsulation ability, which means the thickness of the coating should beincreased also. The single-face thickness of extra-thick coating is 2-14μm.Nowdays, the extra-thick insulation coating is extensive applied abroad,but the research of it in China is rather little.Firstly, the components and performances of two imported coatingswere studied. Both two coatings are amino-baking coatings and thecontent of inorganic component is more than 45%. The adhesion ofcoating affected by the baking temperature actually is related to thecross-linking. The more densification of the coating is and the smootherof the surface is, the better its hardness. In addition, the thermal aging behaviors have been discussed and the proper temperature range from180℃to 230℃was proposed for evaluating the thermal agingperformance. During the thermal aging, FT-IR revealed that the chemicalbond created by cross-linking reaction does not break, and the rupture oftridzine ring of amino resin is regarded as the main facor to destroy thethree dimensional hydrophobic polymer network.Secondly, the organic resin, inorganic pigment, wetting-dispersingagents, solvents and antifoaming agent were selected by experiments andthen the extra-thick insulation coating was prepared. In this coating, thepolyester resin was selected as the prefilming resin and the highlymethylated melamine as well as the methylated high imino melaminewere selected as the crosslinkers. Research on the film forming principleof the varnish has shown that the highly methylated melamine mainlyparticipated in copolycondensation and the methylated high iminomelamine mainly participated in polymerization. This experiment choseBaSO4 and TiO₂ as the main inorganic pigments. TEM and EDS revealedthat both BaSO4 and TiO₂ are submicron size powders. BaSO4 is coatedwith organic agent and TiO₂ is coated with inorganic material. Thewetting-dispersing agents were made up of block copolymer and smallorganic molecules as well as the inorganic dispersant, which can provideboth steric hindrance stabilization and electrostatic stabilization.At the last, the heat resistance was improved by adding the titanate coupling agent and the hardness as well as the stamping ability wereimproved by adding adhesion promoter. Titanate coupling agentimproved the heat resistance by promoting the compatibility of organicphase and inorganic phase. The adhesion promoter increased theinterlayer adhesion and the adhesion between coating and substrate, thusthe densification of the coating was better and the hardness as well as thestamping ability were improved.The synthetic performances revealed that the independentlydeveloped coating can meet the demands of large-scale motor and can beapplied in the field production.