Effects Of Air Dielectric Barrier Discharge Plasma On Properties Of Twaron Fiber Surface And Twaron/PPESK Composites Interface

Aramid fibers are widely used in defense and civil fields due to their high strength, high modulus, high temperature-resistance and good corrosion-resistance. But the interfacial adhesion of Aramid fiber reinforced matrix composites is usually poor because of the fibers having high crystallization, high orientation and the relatively smooth and chemically inactive surface. In order to improve the interfacial adhesion between Twaron fibers and PPESK matrix resin, the research work of the dissertation includes:1. Twaron fibers were treated by acetone solvent. The surface of Twaron fibers before and after cleaning with acetone was investigated by X-ray photoelectron spectroscopy (XPS), FT-IR spectra (FTIR) and dynamic contact analysis system (DCAA). The interfacial adhesion properties of the original and the cleaned by acetone Twaron fibers reinforced PPESK composites were analyzed by interlaminar shear strength (ILSS) and scanning electron microscopy (SEM) measurements. It was found that there was the oily finish with a lot of polar functional groups on the original Twaron fiber surface before cleaning by acetone. The oily finish reduced the interfacial adhesion strength of Twaron/PPESK composites, because the oily finish was a weak layer between the fibers and the matrix. Thus, the oily finish should be removed before Twaron fibers were treated by the air DBD plasma.2. Air DBD plasma treatment is a promising technique in fiber surface modification. In this work, Twaron fibers after acetone cleaning were treated by air DBD plasma at various different sample treatment times and discharge power densities:â‘ The fibers were treated when the plasma discharge power density was set at 27.6 W/cm3 with the sample treatment time varying from 6 s to 12 s and 18 s;â‘¡The fibers were treated when the sample treatment time was set at 12 s with the plasma discharge power density changing from 27.6 W/cm3 to 55.2 W/cm3 and 82.8W/cm3. The surface chemical composition, surface roughness and surface free energy of Twaron fibers under different treating conditions were investigated by XPS, atomic force microscopy (AFM) and DCAA, respectively. The results showed that the air DBD plasma treatment can change the chemical and physical structures of Twaron fiber surface and improve the fiber surface free energy. ILSS, water absorption testing and SEM were used to determine the interfacial properties of the Twaron/PPESK composites. The results obtained from these measurements indicated that the air DBD plasma can improve the interfacial adhesion between Twaron fibers and the PPESK resin. The results also showed that when the sample treatment time was 12 s and meanwhile the discharge power density was 55.2 W/cm3, the interfacial bonding strength of Twaron/PPESK composites had the most distinct improvement, accompanied by the ILSS value increasing from 46.0 MPa for the untreated sample to 61.7 MPa with an increment of 34.1%.