Study On Adhesive Of Mica Tape For High-Voltage Motors

Nowadays, the developments in power electric technology bring forward new and rigor demands on the performances and reliability of insulation systems. As one of the most importmant components for main insulating materials, the adhesive for mica tape in power electronics is subjected to increased thermal, electrical, ambient, and mechanical stresses since the working voltage, the unit power, the working temperature and the geometrical dimensions of electrical insulation systems have all greatly increased. Therefore, new adhesive materials with improved insulating and mechanical performances are in demands.In this paper, a new kind of adhesive with excellent flexibility, thermal stability, and insulating properties is developed for mica tape based on epoxy resins modified with epoxide-functionalized polysiloxanes.The influences of epoxy resins, curing agent, latent accelerators, and polysiloxanes on curing reaction and performances of the adhesive were investigated by differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), dielectric analysis, and mechanical analysis, etc.In this paper, different grades of bisphenol-A epoxy resins and novolac epoxy resin were employed and optimized in the formulation considering the processability, cost, and heat resistance. Methyl-hexahydrophthalic anhydride (MHHPA) was used as hardener. The influences of different latent accelerators on the epoxy adhesive systems were studied and compared. Epoxide-functionalized polydimethylsiloxanes containing phenyl groups (PEPDMS) were employed to improve the flexibility of the epoxy resin. The influences of PEPDMS on the curing behavior, insulating properties, thermal stability, and mechanical performances were investigated. The results showed that both the impact strength and flexible strength were improved with the incorporation of PEPDMS into epoxy resins which may be due to the presence of flexible siloxane linkages and the stiffening effect of rigid phenyl group. The addition of PEPDMS could also improve the thermal stability of epoxy resin with only slight decrease in the glass transition temperature (Tg). The obtained adhesives also exhibit excellent insulating properties with high breakdown strength, high volume resistivity, and low dielectric loss (tanδ) value at 50Hz and 155℃.