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Polymer fibre surface modification by low temperature plasma has received much attention in recent years. The plasma kinetic behaviour and reactive species distribution can be totally different with the existence of fibre. In this work, a 2D axisymmetric fluid model is established to study the interaction between an atmospheric pressure plasma jet and single fibre with different relative permittivity (εr=1.5 and εr=80, respectively). Dividing of the ionization wave is observed when approaching to the fibre, followed by fully wrapping of fibre surface. Afterwards, the ionization wave travels across the fibre and continues to propagate forward. Significant effects induced by the variation of the fibre’s permittivity are observed. For εr=1.5 fibre, the high electric field region shifts from the south pole (SP, closer to the jet tube) to the north pole (NP, opposite side to the SP), but the high electric field region remains at the SP for εr=80 fibre. This is due to the large potential difference on the εr=1.5 fibre surface. Furthermore, the time averaged surface fluxes of the main ions (He+, N2+ and O2+) and excited species (Hes, N and O) are analysed. It is found that the surface fluxes of εr=80 fibre at the NP is significantly higher than that of εr=1.5 fibre. Therefore, increasing the relative dielectric constant of fibre would increase the main ions and excited species surface fluxes at the NP.

In this study, cold atmospheric pressure plasma jet was adopted to glass fibers surface modification with tetraethyl orthosilicate as a precursor. To enhance the interfacial bonding forces of glass fiber reinforced polypropylene (GFRP) composites, SiOx nanoparticles were polymerized on the fiber surfaces. The effect of two factors (the distance between nozzle and fiber (D) and the treatment time (T)) on the interfacial bonding behavior of GFRP composites was studied. The modified fibers and composites properties, including surface topography, chemical composition, wettability and interfacial mechanical properties, were studied comprehensively. The optimal parameters were obtained at D = 17 mm and T = 12 s. Our results indicated that the interlaminar shear strength of GFRP composites was increased by 30.79% compared to control group. Further studies found that plasma treatment introduced larger surface roughness, surface energy and more oxygen-containing functional groups, which was responsible for the interlaminar shear strength improvement.

Atmospheric pressure cold plasmas have great potential for surface functionalization, and the interaction between the plasmas and fibers is essential to understand the underlying physics. In this Letter, the penetration pattern and mechanism of an atmospheric pressure plasma jet (APPJ) interacting with different spacing fiber scaffolds were studied by both experiment and modeling. The intensified charge coupled device images showed that APPJ induced a radial surface streamer on the windward side of the scaffold and another axial forward streamer on the opposite side. Propagation distance of both the radial and axial streamers diminished as the spacing decreased. Similar trends were predicted by a 2D fluid model. The simulation results indicated that the high electrical field carried by the streamer head in APPJ was allowed to pass through the gap for large spacing scaffold, while it was blocked by high intensity charges at small spacing. Instead, one axial streamer was generated in the latter case. The physical insight on the penetration mechanism of plasma jet interacting with fiber array in this Letter may contribute to improve treatment uniformity of plasma technology.

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