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Carbon fiber and its composites are widely used as structural materials due to their excellent mechanical properties. However, the chemical inertness of carbon fibers restricts their further application. In this paper, we implemented that the modification of carbon fiber via coating aramid nanofibers based on pre-treatment of carbon fiber surface by dopamine. At the same time, the effects of modified fibers on the properties of paper-based materials were investigated. It was found that pre-treatment of carbon fiber contributed to the cationization of the surface of carbon fiber, and further assisted the coating of aramid nanofiber by electrostatic adsorption. The surface morphology, chemical composition, hydrophilic property and mechanical properties of carbon fiber paper-based material were characterized by scanning electron microscopy(SEM), fourier transform infrared spectroscopy(FTIR), contact angle tester and tension tester. The results showed that the best coating effect on carbon fiber was achieved when the concentration of aramid nanofiber is 0.2% the best deposition effect when the 0.2% concentration of nano aramid fiber. The carbon fiber paper-based material modified by aramid nanofiber has good hydrophobic properties(CA=112.4°C) and mechanical properties(6.74 MPa). [ABSTRACT FROM AUTHOR]

Aramid nanofiber (ANF) has the characteristics of light weight, insulation, high strength, high temperature resistance, etc., which is widely used in electrical insulation, battery electrodes and other fields. In order to adapt to more demanding environments, it is particularly important to improve the basic mechanical properties. Natural silk fibers have ultimate tensile strength of up to 300～400 MPa, elongation at break of 26% and toughness of 70～78 MJ·m-3.In recent years, studies have proved that silk fibroin (SF) can effectively enhance polyurethane, cellulose, graphene oxide and other substances. ANF was prepared via the splitting of macro aramid fiber, which was further composited with the SF additives obtained by degumming and dissolving the silkworm cocoon to form ANF/SF composite films. The influences of the SF on the micromorphology, chemical structure, mechanical property, thermal stability, wettability, and insulation property of the ANF/SF composites were investigated. The results suggest that SF can densify the microstructures of the ANF films and can effectively improve the interfacial adhesion between the individual nanofibers. For this reason, the mechanical and insulating properties of the prepared composite films are greatly improved. When the amount of SF is 0.6 wt.%,the tensile strength, toughness, and elongation at break of the ANF/SF film are 261.4 MPa, 38.8 MJ·m-3,and 22.7%,respectively, which are 157%,384%,and 241% higher than those of pure ANF film.When the SF content is up to 1.0 wt.%,the dielectric breakdown strength is 61.9 kV·mm-1,which is 153% higher than ANF film. [ABSTRACT FROM AUTHOR]

Abstract With soft-touch, lightweight, excellent temperature resistance and insulating performance, aramid mica paper is widely used in special motors 'transformers and other electrical equipments. In this paper, aramid mica paper was prepared by using white mica, meta-aramid chopped fiber and meta-aramid fibrid as skeleton and bonding components respectively. The effects of aramid fibers ratio, dispersant dosage, mica content and mica particle size on mechanical properties, insulating properties, micro-structure and temperature resistance of paper were studied. The results showed that the optimal process parameters were as follows: the mass ratio of fibrid to chopped fiber was 7:3 the amount of PEO was 0.5wt%, the mass fraction of mica was 50 wt%, and the size of mica was 120~150μm. [ABSTRACT FROM AUTHOR]