Technology Of Producing High Performance Mica Paper Composite And Research Of Its Enhancement Mechanism

As insulation material mica is used in kinds of electrical and motor industry, showing superior performance. With the exhausting of large mica resource, mica papers made of mica flakes become main mica insulations because of its uniform width, small ripple dielectric strength and high initial voltage of corona. Mica papers are made from mica flakes using paper making machine. They are formed by static electricity and Van der Waals force which are too small to provide enough strength to directly use without any binders and reinforcement materials. However, the adding of binders and reinforcement materials reduces contents of mica in the material, so as to the insulation property. For the purpose of maintaining the insulation properties and improving mechanical strength, high strength composite material is made by mica and other material. Aramid fiber has extremely high strength and excellent insulation performance. The composite of mica and aramid fiber can improve strength of material.In this paper,8% of aramid fibers are added to mica pulp to make aramid mica paper. The strength of interface bonding is improved by proper mica material, pulp making methods, mica surface modification, aramid fiber dispersing and modification, so as to the strength of composite. Properities of aramid/mica paper with 8% of aramid fibers contents are similar to products of Dupont which 50% of aramid fibers were added. Process of producing can be simplified by manufacturing of this kind of composite without process of gluing and reinforcement. Through the experiments best conditions of process parameters are determined, conclusions as follows are obtained:1. Calcinations chemical pulp making method is chosen as the better pulp making method by the properties of mica paper and aramid mica paper made of those pulps. Particle size of mica pulp is discussed to get the conclusion that wide particle size range is better for the property improvement of composite material.2. Avoiding ions, SS and alkaline water which can effect the strength of aramid/mica paper is the basement to produce high performance paper. Kinds of modifiers are used to the modification of mica. Among those modifiers polyacrylamide and starch have excellent modification effects. Starch if better than polyacrylamide and cationic starch get the best. Aramid mica paper made of mica flakes modified by starch modifier is 277.5% times better than that without any modification. The best conditions of adding modifier are 10kg/t dosage,16% concentration of pulp,30min modification time. The adding of modifier has no effects to the dielectric property of composite material. 3. Among the modification methods of aramid fiber ultrasonic modification has benefit to the improvement of surface activity and micro fibrosis. Meanwhile, complementary with silane coupling agent modification, surface force of fibers and strength of materials are improved. Composite paper made of modified aramid fibers and mica flakes have a tensile strength of 28.56N/cm compares with 23.97N/cm, 19.1% high than without any modification of aramid fibers. PEO combining with dodecylbenzenesulfonic acid sodium is benefit for the dispersing of aramid fibers which can improve the uniformity and softness of composite material.4. Pulp mixing process is better than the other two processes for the paper making of composite material, and best process parameters are determined.5. Hot press process is also discussed so as to get the best process parameters. After hot press tensile strength, dielectric strength, fold resistance degree, density and softness of aramid mica paper are tested and compared with NOMEX 418 including mechanical strength, high temperature resistance, insulation property and stability. Among those properties, aramid mica paper has better tensile strength and dielectric strength, same high temperature resistance and stability, just a little poor in volume resistivity and dissipation factor.6. The enhancement mechanism of aramid mica paper compound is discussed. The modification of mica flakes and aramid fibers can improve interface bonding performance, plasticity and overall performance.The producing of aramid/mica paper is important to mica insulation material. Firstly, the emergence of aramid mica paper ends the situation of without concerned high performance products. Secondly, aramid/mica paper can reach a high strength which can be usded directly without any other reinforcement material. Improvement of mica contents can extense application time of material and improve security. With proper process mica insulation can form easily. Thirdly, the use of aramid fiber is useful to get thinner insulation which can be used in smaller electrical equipments. Finally, small amount of aramid fiber contents is benefit to cut the costs. It is significance to enlarge the category of mica insulation productions.