| Due to the intrinsic features of natural mica and aramid fibers,aramid-mica paper possesses high mechanical properties and excellent dielectric properties,thus being applied in communication defense,transportation and house-hold appliances.Early United States patents have mentioned with the fabrication of aramid-mica papers.Today the Dupont also introduces a new aramid-paper with a large number of mica,and this kind of paper has higher reliability and insulation life.However,there are no domestic aramid-mica products yet.Under the rapid development of China electrical industry including the accelerating railway process and the updating transmission technologies,insulation materials tend to have higher mechanical properties,insulation properties et al.Therefore,it is imminent that making more contribution on the studying of high-performance aramid-mica insulated paper.In this paper,the research on the forming technology of aramid-mica paper was carried out.Firstly,the comparative analysis between meta-aramid fibrids and para-aramid fibrids was completed including its difference of morphology and feature parameters.And the integrated properties of two kinds of aramid-mica paper were also discussed.From the results of research,It was shown that the para-aramid fibrids had better film forms,more easy to disperse and embed tangles fiber and rigid materials such as inorganic particles and m-aramid fiber.The width of p-aramid fiber in 30~60?m accounted for 25.5% in total fiber weight,when the width of m-aramid fiber was just accounted 12.9%,which showed para-aramid fibrids has a larger specific surface area,help to play its mechanical properties.The tensile strength of p-aramid-mica paper had improved 45.1% than m-aramid-mica paper,and also the p-aramid-mica paper had higher thermal stability.Mica particle size and distribution produce influenceon the performance of paper in a certain.The experimental results showed that the aramid-mica paper with wide particle size distribution range of mica had higher tensile strength and electric strength than the aramid-mica paper with homogeneous large diameter mica and small particle size of mica.Secondly,the paper analyzed the properties of aramid-mica paper with different ratio of aramid fiber and mica,and explored the function of different forms of aramid fibers.The two kinds of paper include fibrids-mica paper(F-M)and aramid chopped/fibrids mica paper(A-M)were prepared.Experimental results showed that the maximum tensile strength of A-M paper and F-M paper reached 9.12 N/cm and 9.38 N/cm respectively at the 50% fiber content.When under the same fiber content,the tear strength of the A-M composite paper was greater than the F-M composite paper,but its insulation lower than F-M paper.With the increasing of fiber content,the two composite papers became hydrophobic better and better,and its decomposition thermal temperature gradually decreased,but still kept good thermal stability.Therefore,the microstructure of these aramid-mica composite papers can be summarized that the fibrids could enhance the inter-facial adhesion between different mica flakes,the floc could destroy the adhension because of its performance at low fiber content,and would forming a large number of reinforced floc-frameworks as the addition of fiber were increasing.Finally,the research also studied the modification of mica by dopamine.At first,The experiment test by using AFM,XRD and FT-IR was carried out.The image of AFM showed the morphology of mica after modifying had sags and crests;The FT-IR spectra of the peak at 1629cm-1 increased weakly,which proved the content of dopamine depositing on the mica raised;The XRD showed the distance of mica crystal enlarged a little.Next,the coated mica composite papers were tested.The results showed the paper had best properties when using the 1.5% dopamine,its tensile strength had improved from 16.35N/cm to21.87N/cm and dielectric strength reached 16.04kV/mm.And the coated paper had better adhesion and structure stability. |
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