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Kevlar pulp treated with low-temperature plasma and nano cellulose fibrils (NCFs) have been introduced as reinforcements in the preparation for composite insulating paper with low relative permittivity, dielectric loss, good mechanical properties, and thermal stability. More polar groups of Kevlar fibers could be exposed after plasma treatment. Results showed that the relative permittivity of the composite paper containing 20% Kevlar pulp, 10% NCF, and 70% softwood pulp is decreased by 29.6% and the dielectric loss is decreased by 43.2% at 50 Hz, 25°, compared with the conventional paper formed by pure softwood pulp. The change was due to the introduction of Kevlar pulp with intrinsic low dielectric constant and loss, which decreases the whole polarizability of the paper. The mechanical properties of the composite paper became worse after introducing 20% Kevlar pulp. About 10% NCF can work as a mechanical reinforcement to compensate for the tensile and Yang's modulus loss. Scanning electron microscopy results showed that NCF could fill the void defects and improve the interface bonding of the fibers to enhance the paper mechanical properties. The composite paper also had better insulating and thermal properties than the conventional paper. It has been concluded that the Kevlar pulp/NCF/softwood pulp composite paper has the potential to replace the pure softwood paper for the application of high-voltage ac transformer insulation.

Abstract: Kevlar pulp reinforced epoxy composites were prepared by compression molding. The friction and wear behavior of Kevlar pulp reinforced epoxy composites against stainless steel under dry sliding and water lubricated conditions was comparatively evaluated on an M-2000 friction and wear tester. The effects of Kevlar pulp content on tribological properties of the composites were investigated. The worn surfaces morphologies of neat epoxy and its composites were observed with a scanning electron microscopy (SEM) and the wear mechanisms were discussed. The results show that the incorporation of Kevlar pulp into epoxy contributed to improve the friction and wear behavior considerably. The optimum wear reduction was obtained when the content of Kevlar pulp is 40vol.%. Neat epoxy and its composites sliding against stainless steel register lower friction coefficients and wear rates under water lubricated condition than under dry sliding, owing to the boundary lubricating and cooling effect of distilled water. Adherence, plowing and plastic deformation are dominant under dry sliding, and abrasive wear is dominant under water lubricated condition. [Copyright &y& Elsevier]

Solutions of rare earth modifier (RES) and epoxy chloropropane (ECP) grafting modification method were used for the surface treatment of Kevlar pulp. The surface characteristics of untreated and treated Kevlar pulp were characterized by Fourier transform infrared (FT-IR) spectroscope. The bend strength and block-on-ring wear behavior of Kevlar pulp/epoxy composites were comparatively investigated. The worn surfaces of the composites were examined by scanning electron microscope (SEM). The results show that surface treatment can effectively improve the interfacial adhesion between Kevlar fiber and epoxy matrix. Thus, the bend strength and wear resistance were significantly improved. The RES surface treatment is superior to ECP grafting treatment in promoting interfacial adhesion between Kevlar fiber and epoxy resin. [ABSTRACT FROM AUTHOR]

In this work, the friction and wear properties of Kevlar pulp reinforced epoxy composites against GCr15 steel under dry sliding condition were evaluated on a reciprocating ball-on-block UMT-2MT tribometer. The effects of Kevlar pulp content on tribological properties of the composites were investigated. The worn surface morphologies of neat epoxy and its composites were examined by scanning electron microscopy (SEM) and the wear mechanisms discussed. The results show that the incorporation of Kevlar pulp into epoxy contributed to improve the friction and wear behavior considerably. The maximum wear reduction was obtained when the content of Kevlar pulp is 40 vol%. The friction coefficient of epoxy and its composites increased with load while increase in the sliding frequency induced a reverse effect. Fatigue wear and scuffing were notable for the neat epoxy. The fatigue cracks were greatly abated when the filler content was 40 vol%. The wear grooves appeared on the worn surface at higher filler content. [ABSTRACT FROM AUTHOR]