Research On The Application Of Dielectric Barrier Discharge Low Temperature Technique In Surface Modification Of Para-Aramid Fibers

Para-aramid fiber is a compound linear chain macromolecule material which has high crystallization and high orientation. As it has the properties of low density, high strength, good toughness, excellent thermal-resistance, chemical corrosion-resistance and good impact resistance, Para-aramid fiber has been widely used as an reinforce composite material in the fields of aviation, automobile, shipbuilding. However, owing to the smooth surface and chemical inertness, the fiber’ interfacial adhesive performance with the resin is limited and the wettability properties of the fiber are low, which are to disadvantage of its applying to the composite materials. So the surface modification of the Para-aramid fibers becomes a must. The paper is focused on the application of dielectric barrier discharge low temperature technique in surface modification of Para-aramid fibers. The experiments adopt Argon. Argon/Oxygen, Argon/Nitrogen、Helium/Oxygen, and research on the effect of treated power, treated time and flux. In addition, the time effect of the dielectric barrier discharge has been detected in the paper.The first chapter of the paper is a review, and the main experiment parts are from chapter2to chapter5. In the first chapter, the recent researches on the application of dielectric barrier discharge (DBD) technique in surface modification of aramid fibers were summarized, the mechanism, the characteristics and the main domestic devices of the DBD technique were introduced. Besides, the paper has a brief introduction on the wettability and adhesive performance improvement of aramid fiber through DBD plasma surface modification.The Chapter two is focused on the influence of argon dielectric barrier discharge plasma on the adhesive performance and wettability of Para-aramid fibers and three parameters including treated power, exposure time and argon flux were detected. The interfacial shear strength (IFSS) was greatly increased by28%with300W,60s,2L·min-1argon flux plasma treatment. The content of oxygen atom and oxygen-containing polar functional groups were enhanced after the argon plasma treated so as the surface roughness, which contributed to the improvement of surface wettability and the decrease of contact angle with water. However, long-time exposure, exorbitant power or overlarge argon flux could partly destroy the prior effects of the treatment and damage the mechanical properties of fibers to some degree.In chapter there, the effects of different plasmas including Ar, Ar/O2and Ar/N2as well as their flux on the surface modification of aramid fiber are studied. Micro-bond test, contact angle analysis, X-ray photoelectron spectroscopy (XPS) and atomic force microscope (AFM) are utilized to characterize and compare the variations of surface adhesion, wettability, chemical composition, functional groups and surface roughness of treated aramid fibers, respectively. The results indicates that the type of plasmas and their flow rate would both influence the effects of surface modification, which determines whether the surface etching or the activating of functional groups plays dominant role in the surface modification of aramid fibers.In Chapter four, the time effect of dielectric barrier discharge plasma technique is detected. After Ar, Ar/O2, Ar/N2treatment, the adhesive and wettability performance would be worse with the extension of standing time, and the decrease of performance would be most serious with the pure Ar plasma treatment. The polar elements and polar functional groups contents would be decreased after4weeks, and whatever plasma types would contribute to the same trend. Compare to the pure Ar plasma treatment, when the second gases add to the argon, no matter it is O2or N2, would slow down the time effect to some degree especially the N2.In chapter five, it is focused on influence of helium/oxygen dielectric barrier discharge (DBD) plasma on the adhesive performance between fiber and matrix, the wettability property of para-aramid fibers. Compare to Ar, He has the high thermal coefficient, and with the same current and voltage, the helium would produce more heat and high temperature, which would cause better improvement with the surface performance. Three parameters were investigated in this article including treatment power, exposure time and helium/oxygen flux. The optimum experimental condition was300W,90s,3/0.03L· min-1helium/oxygen flux, under which condition the interfacial shear strength (IFSS) between fiber and epoxy was greatly increased, the content of oxygen atom and oxygen-containing polar functional groups as well as the surface roughness were enhanced, which contributed to the decrease of the water contact angle.