Effects of Twaron fiber surface treatment by air dielectric barrier discharge plasma on the interfacial adhesion in fiber reinforced composites

Twaron aramid fiber is treated by air dielectric barrier discharge (DBD) plasma at atmospheric pressure. The relation between the interfacial adhesion in Twaron fiber reinforced thermoplastic poly(phthalazinone ether sulfone ketone) (Twaron/PPESK) composites and this surface treatment has been established and discussed. This paper reports the effectiveness of air DBD plasma treatment on the improvement of interfacial adhesion in Twaron/PPESK composites from two aspects: the oxidation as well as etching modifications of naked (without finish) Twaron fiber surface and the oily finish removal of original Twaron fiber surface, as characterized by means of X-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM) and dynamic contact angle analysis (DCAA). The interlaminar adhesion property is determined by interlaminar shear strength (ILSS) measurement. Results show that the 27.6 W/cm3, 12 s air DBD plasma treatment is responsible for the introduction of reactive functional groups (such as C–O, O=C and O=C–O) and the increase of surface roughness in the case of naked Twaron fiber, and it can also effectively remove the oily finish on the original fiber surface. All these effects induced by the plasma on Twaron fiber surface should account for the noticeable enhancement of the interfacial adhesion between treated fibers and PPESK matrix.