Research On The Mica/Chitosan And Mica/Epoxy Resin Hierarchical Composite Insulating Materials

The demand of power has been increasing with the fast development of world economy for which the high voltage motor of large scale plays a more and more important role.The main insulation of current high voltage motor is mica tape insulation.This article takes the stator insulation of high voltage motor as the research object and prepares a mica composite insulating material of high performance through the blending of mica powder and adhesives with the integration of bionic structure for nacre in shell to eliminate the supporting material.This article prepares the mica powder under the best modified conditions for different modifiers through the research on the best modified condition on the surface of mica powder and prepares two kinds of mica composite insulating materials of high performance with chitosan and epoxy resin as the adhesives for the test of the mechanical properties,electrical properties and thermal conductivity.It also analyzes and compares with the specified data of GB/T 5019.12-2017 national standard?hereinafter referred to as the mica tape standard?for mica powder.To solve the problems of low filler level,bad dispersibility for the mica powder in the basal bodies of chitosan and epoxy resin,this article applies the two coupling agents which are JFCG5 and JFCG6 for the surface modification of mica powder respectively.Through the index of pre-evaluation on the effect of modification,it conducts a research on the influence of different modification temperatures,time,and modifier dosages on the effect of modification.The result shows that the modification time of 1h is the best condition for the process with the 1.0%of mica powder as the modifier dosage and 90?as the modification temperature when JFCG5 is applied as the modifier.The modification time of 1.5h is the best condition for the process with the 1.2%of mica powder as the modifier dosage and 90?as the modification temperature when JFCG6 is applied as the modifier.The oil absorption of mica powder decreases for 30.8%and the dispersibility in kerosene increases for 26.9%after modification.Research is conducted for the three different preparation processes of mica and chitosan composite insulating materials with chitosan as the adhesive.The test of mechanical properties,electrical properties,and thermal conductivity has been conducted for the mica chitosan composite insulating materials after the selection of the best preparation process through the analysis on the topography image of section.The result shows that the mica forms a close stacking structure in the chitosan by the observation on the topography image of section in composite insulating materials after the mixture of 5%nano-cellulose and 50%mica powder.Its thermal conductivity reaches 0.71 W/?m·k?which improves for 2.5 times compared with the mica tape products on the market.The thickness of the composite insulating material can be controlled by the film coating process with the thickness of 0.08?0.12mm which is better than 0.15mm defined in the mica tape standard.Its mechanical property reaches122.20 N/10mm which is better than80 N/10mm defined in the mica tape standard.Its breakdown field strength is18.53k V/mm which is better than 15 k V/mm defined in the mica tape standard.Its order of magnitude for the electric volume resistivity of composite insulating materials is10¹⁰?·m which keeps a high insulating property.The stiffness of 17 N/m meets the requirement of the mica tape standard which defines that the stiffness must be smaller than 50 N/m.Research is conducted for the mechanical properties,electrical properties,and thermal conductivity of the composite insulating materials of mica and epoxy resin with epoxy resin as the adhesives.By the observation on the topography image of section in the composite insulating materials,it is discovered that mica is gradually formed with a compact stacking structure in the epoxy resin with the increase of filler level of mica.The thermal conductivity reaches 0.57 W/?m·k?when the content of mica reaches 80%which is improved for 1.9 times compared with the mica tape products on the market.when the filler level of mica reaches 50%,the breakdown field strength is improved and reaches24.64 k V/mm which is better than 15 k V/mm defined in the mica tape standard;the relative dielectric constant of epoxy is between 3?4.After the supplement of mica,the relative dielectric constant of the composite insulating material is between 6?8.Under the environment of low temperature,the loss tangent of the composite insulating material is kept under 2%and the relative dielectric constant and the tangent loss are kept small.The electric volume resistivity of the composite insulating material is generally kept at the magnitude order of 10¹⁴?·m with the preservation of high insulating property.If the tensile strength of the composite insulating material is transformed as yield load,it shall meet the mica tape standard with the yield load being in the scope of 1600?2700N.In summary,the two mica composite insulating materials of high performance prepared in this article meet the basic requirement defined in the standard with the breakthrough in the direction of thermal conductivity and supporting materials for the mica tape.This composite insulating material abandons the supporting materials of mica tape available and improves the thermal conductivity of the mica composite insulating materials,It provides an important value of reference for the research and development of new mica tape products with an important significance for the development of mica tape.