Effect of Online Plasma Treatment on Fiber Surfaces and Mechanical Properties of Continuous Basalt Fiber-Reinforced Polypropylene Composites

Continuous basalt fiber-reinforced polypropylene (BFRP) composites exhibit excellent mechanical properties, chemical stability, and environmentally friendly characteristics, making them one of the most promising types of composites. However, basalt fibers’ (BFs) smooth and chemically inert surface leads to poor interfacial bonding between the fibers and resin, significantly hindering their rapid development. Most existing fiber surface treatment methods are conducted discontinuously, making them unsuitable for the continuous online production of composites. This study developed an online plasma continuous fiber surface treatment device to integrate fiber surface modification with preparing continuous BFRP composites using the melt impregnation method. Orthogonal experiments were conducted to assess the influence of plasma discharge power, treatment distance, and gas pressure on the effectiveness of fiber surface treatment. Additionally, the working gas type’s impact on basalt fiber (BF) modification was explored. X-ray photoelectron spectroscopy (XPS), Atomic force microscopy (AFM), Scanning electron microscopy (SEM), and mechanical property tests were employed to comprehensively evaluate the surface morphology and chemical composition of the treated fibers, as well as the mechanical properties of the composites. The results revealed that the surface roughness (Ra) of the fibers treated under optimal process parameters increased by 34% compared to the control group. The interlaminar shear strength (ILSS) of the BFRP composites increased by 104%, the tensile strength of standard samples improved by 10.28%, bending strength increased by 9.47%, and impact strength rose by 18.19%, all compared to the control group. These findings indicate that plasma treatment technology can be effectively applied to online fiber modification, significantly enhancing the mechanical properties of the composites.