217 / 2018-09-20 19:48:31

Preparation and Properties of Nano-Cellulose Modified Natural Ester Liquids

thermal properties, dielectric properties, nano cellulose,natural ester liquids

Nanotechnology is widely used in improving the thermal conductivity and insulation properties of materials. Vegetable insulating oil, as dielectric liquid, with high burning point and renewable, has been widely applied in power distribution transformer. However, the poor heat dissipation of vegetable insulating oil reduces the service life of transformers and restricts its application in higher voltage level. Nanotechnology is widely used in improving the thermal conductivity and insulation properties of materials. The development of nano vegetable insulating oil is not only an extension of the research and application, but also a new research topic in nano dielectric. The dielectric and breakdown performance of plant insulating oil are two important indicator to characterize its insulation performance, which directly affects the safety and reliability of transformers. Its dielectric properties include dielectric constant, electrical conductivity and dielectric loss factor, reflecting the dielectric polarization, insulation resistance and internal energy loss of the liquid dielectric under the electric field. At present, the research direction of nano insulating oil still exist many problems, include two key issues: (1) Whether the nanoparticles can give consideration to the insulation performance and improve the heat dissipation performance of vegetable insulating oil. (2) The molecule structure of vegetable insulating oil is different from mineral oil, its dielectric conductivity, high dielectric loss, lack of study on the mechanism of the influence of nanoparticles on the electrical conductivity and dielectric loss factor problem. This paper introduced the preparation method of nano cellulose modified plant insulating oil, plant insulating oils with different concentrations of nano cellulose were prepared and the influence of nano cellulose on electrical and thermal performance of plant oil were investigated. Nano cellulose was prepared by chemical modification method which modified nano cellulose extracted from raw pulp by silanization modification and dispersed in insulation oil and compared with the sample prepared with nano cellulose which were not modified. Characterize nanoparticle dispersion by ZETA potential. The result shows that nano cellulose after chemical modification can be uniformly dispersed in plant insulating oil and that the sample been modified has a much better dispersion stability than the unmodified sample. The DC breakdown voltage ,dielectric constant, dielectric loss and volume resistivity of plant insulation oil with different concentration of nano cellulose were tested, and so was the thermal conductivity. The result shows that low proportion of nanodoping can effectly increase breakdown voltage, relative dielectric constant rise slightly after doping, electrical conductivity of nano insulating oil decreases as the doping concentration increases and the dielectric loss factors of vegetable insulating oil increases slightly after doping. The thermal conductivity test result shows that the doping of nano cellulose can improve the thermal conductivity of vegetable insulation oil, and as temperature increases the thermal conductivity decrease slightly from 25℃ to 90 ℃. After all, the above research provide a new idea and experimental basis for the preparation of nano cellulose modified vegetable insulation oil with both excellent insulation and heat dissipation properties. And the above research work will provide theoretical support and experimental basis for the preparation of nano vegetable insulating oil with excellent electrical performance, low dielectric loss, and improved thermal performance.