| According to the current development tendency from domestic and foreign motor,electrical appliances, transformer and IT information industry to the high-tech products of“high voltage, high frequency, high efficiency, energy conservation, compact type”, the corecomponent-enameled wire, is required to be composite and high performance. Thus, based onthe aborative choices of insulating varnish used in this study, the nano-SiO2was surfacemodified and then added to the insulating varnish for modification. The “enameled wire ofnano-composite high performance” was trial-produced by the “three coatings” process, andthe conditions and parameters of process and technology were studied preliminarily. The maintasks are listed as follows:(1) Based on the sufficient investigation, the polyester (PE), polyesterimide (PEI) andpolyamideimide (PAI) were chose, and their compatibility was studied. It is found that thecompatibility between PE and PEI, PEI and PAI is good, while the compatibility between PEand PAI is poor.(2) The nano-SiO2was surface modified by KH550using solution method and then themodified nano-SiO2was added to the insulating varnish for modification. The effect ofmodifier content and reaction time on the modification reaction was studied. The FTIR resultsshow that the KH550is grafted on the surface of nano-SiO2via covalent bonds. The TEMresults indicate that the modified nano-SiO2particles are well dispersed in ethanol. The XRDresults display that there is little effect of the modification process on the structure ofnano-SiO2. The modification effect of this method is the best when the modifier content is5%and the reaction time is4-5h.(3) The influence of dispersion methods and modified nano-SiO2contents on themodification effect of the insulating varnish was studied. It is found that the modifiednano-SiO2is well dispersed in the insulating varnish with the method of ultrasonic dispersionand high-speed shear. By comparison, the effect of ultrasonic dispersion is better than that ofhigh-speed shear. There is important influence of the modified nano-SiO2contents on itsdispersion stability. The modified nano-SiO2shows good dispersion with its content≤5%.The dispersion uniformity decreases significantly and the agglomeration phenomenonbecomes worse when the content of modified nano-SiO2≥7%.(4) Three projects and six formulas were designed, and the enameled wire of nano-composite high performance was trial-produced by the “three coatings” process. The effect ofinsulating varnish type, nano-SiO2contents and process on the performance of enameled wirewas studied. Project one: heat resistant PE (level155) was used as primer; the middle layer of paintused PEI (level200) as base paint, the nano paint modified by the modified nano-SiO2(according to the number of trial) as intermediate layer paint; PEI (level200) was used as thesurface paint. Painting numbers:8, the thickness of each painting film was distributedaccording to the maximum film thickness ratio, that is:2primers,20-25%of total paintingfilm,4intermediate layer paints,50-60%of total painting film,2surface paints,20-25%oftotal painting film. The results of project one show that:①there is great influence ofinsulating varnish type on the main performance of enameled wire, and they are PE, PEI andPAI in ascending order of degree.②the influence of nano-SiO2contents: when the contentsincreases from3%to5%, the softening breakdown temperature and breakdown voltage israised about20℃and1000V, respectively.Project two: heat resistant PE (level155) was used as primer, the nano paint modified bythe modified nano-SiO2(according to the number of trial) as primer; the middle layer of paintused PEI (level200) as base paint, the nano paint modified by the modified nano-SiO2(according to the number of trial) as intermediate layer paint; PEI (200℃) was used as thesurface paint. Painting numbers:9, the thickness of each painting film was distributedaccording to the maximum film thickness ratio, that is:3primers,20-25%of total paintingfilm,3intermediate layer paints,50-60%of total painting film,3surface paints,20-25%oftotal painting film. The results of B*-1samples prepared by project two indicate that theperformance of enameled wire is increased more obviously with the further increase ofnano-SiO2contents.Project three: heat resistant PE (level155) was used as primer, the nano paint modifiedby the modified nano-SiO2(according to the number of trial) as primer; the middle layer ofpaint used PEI (level200) as base paint, the nano paint modified by the modified nano-SiO2(according to the number of trial) as intermediate layer paint; PEI (220℃) was used as thesurface paint. Painting numbers:12, the thickness of each painting film was distributedaccording to the maximum film thickness ratio, that is:4primers,20-25%of total paintingfilm,6intermediate layer paints,50-60%of total painting film,2surface paints,20-25%oftotal painting film. The thermal shock, softening breakdown temperature and breakdownvoltage of C*-1samples prepared by project three are qualified and the samples arecorona-resistant. However, the results cannot meet the requirements. |
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