Study On A Moisture-proof Insulating Composite Coating Caterial Work In High Temperature

Thermal-couple is a kind of high-temperature inspective sensor widely used in electronic industry, whose inspective temperature range is 0℃～1000℃or higher. The seal situation of thermal-couple will influence many of this characters.The armoured thermo-couple used in this experiment has 4 chromel-nisiloy bars in a stainless steel tube, and the insulator between outer tube and the bars is MgO. A high performance insulating coating material used at the end of the thermo-couple is studied in this paper. The thermo-couple sealed by the coating material can work for long time under 95ï¼…relative humidity at 40℃and can keep the resistance upon 1 MΩwhen the temperature suddenly increase to 400℃. However, traditional organic silicon doesn't have such performance.A organic-inorganic composite was studied in this thesis. The organic component adopted methyl phenyl silicone, which had a better high-temperature resistance. The low melting point sealing glass was used as inorganic component. An certain amount of clay and talcum were introduced to modify the coating property. The coating material has a low shaping temperature, a high heat resistance temperature, and can combine well with both stainless steel tube and MgO filler.Through investigating the glass filler's electronic performance, expansion coefficient, softening temperature and sintering temperature, the effect of the lead oxide glass system (PbO-ZnO-B₂O₃-SiO₂) and the phosphate glass system (P₂O₅-ZnO-BaO) as inorganic filler on the coating performance was systematically studied. It was found that the coating performance with the lead oxide glass was obviously better than that of the coating with phosphate glass. The PbO-ZnO-B₂O₃-SiO₂ system glass was chosen as the filler of the coating composite. The result shows that the solidification temperature of the sample B-13 is 220℃, and its surface resistance maintains 10×10⁷MΩat 500℃.The best quantity of the introduced glass filler was discussed in the thesis, the effects of the glass filler granularity and the coat thickness on the surface resistance and the high-temperature resistance, and got the best coat recipe: B-13-1, comprise with(wtï¼…): glsss filler(D₅₀=0.94μm) 30, organic silicon30, impregnant 30, clay 4.0and french chalk6.0. The thermal-couple check bar sealed with B-13-1 coat can be checked under 40℃and 95ï¼…relative humidity for 40 hours, and the isolating property was still good.