The Study On Interfacial Properties Of Aramid Fiber Modified With Air Plasma Method Of Dielectric Barrier Discharge

Aramid fiber is a compound linear chain macromolecule of high crystallization and high orientation, as a reinforce composite, it can have a prospect used extensively in the fields of aviation, automobile, shipbuilding and exploiture of special type res because of high strength, high modulus, high temperature-resistance, good corrosion-resistance and good impact resistance. As the special structure of Aramid fiber, it is difficult to adhere to resin because of a lower hydrophilicity. For exerting the outstanding mechanical performances, we take a surface modification on aramid fiber to enhance the fiber-matrix interfacial adhesive strength.The common methods of surface modification on aramid fiber are chemical and physical methods, such as chemical etching, chemical surface grafting, plasma treatment,γ-radial radicalization, coating method and so on. In these methods, cold plasma treatment is small to environmental impact, excitateding the reaction which is difficult to occur in routine condition and only impacting the low surface layer not affecting the basic fiber properties. The plasma treatment is a technique which is etching and cleaning the surface layer of fiber, and then adhering to polar group. As one of the plasma treatment, dielectric barrier discharge(DBD) can achieve atmospheric discharge and continuous treatment, it is used widely and possible to carry out the industry production.This article introduces the surface modification of aramid fiber by DBD plasma, choosing the different discharge power and treatment time as the reaction condition. The surface of aramid fiber is observed by scanning electron microscopy(SEM), hydrophilicity measurements and X-ray photoelectron spectroscopy(XPS). The tensile properties of aramid fiber are examined by a tensile tester and verify the data by means of statistics, fiber pull-out test is used to evaluate the influence of the plasma treatment on the interfacial properties.By means of a series of experiments and analysis, we can get the conclusions as follow:(1) The SEM indicates that the fiber surface is smooth before the treatment and becomes more rough, have more surface area and enhance the mechanical binding strength between fiber and matrix; surface chemical modification induced by air plasma treatment were determined by XPS analysis, confirming the surface grafting of oxygenous species during the treatment. In the hydrophilicity measurements, aramid fiber after treatment can better adhere to water molecules with hydrogen bond, and the aramid surface after cold plasma treatment can be formed exiguous grooves and become more rough to keep the water molecules easier into capillary holes.(2) In the initial stage of discharge, the surface of aramid fiber is grafted on oxygenous species by air plasma treatment, then, the surface becomes more rough along with the treatment time; finally, the oxygenous species will be shedded when the treatment time is longer, and the surface is more and more rough.(3) After the plasma treatment, the tensile strength, initial modulus and elongation at rapture of the fibers are basically invariable with the time of treatment; and the interfacial shear strength increases after plasma treatment, the results show that a mass of oxygenous species are interactional with the matrixes, and the rough surfaces enhance the binding force, bringing on the interfacial shear strength increases obviously.