Aramid fibers have been applied in various fields such as aviation and aerospace due to their excellent properties such as high specific modulus, high specific strength, and fatigue resistance. However, from its structure, it can be seen that it is a highly oriented crystalline micro area, smooth surface, dense lattice, few active points, high crystallinity, weak intermolecular hydrogen bonding, low transverse tensile strength, and easy to fibrotic polyamide fiber material. Due to the steric hindrance effect of the large benzene ring in the main chain, it is difficult for the phthalimide group to react with the atoms or groups of the resin during the preparation of composite materials. The fiber surface exhibits significant chemical inertness, low interfacial bonding energy between fibers and resin, poor adhesion and wettability, and poor interfacial bonding between the two phases, which affects the comprehensive performance of composite materials and limits its wide application in composite materials. Therefore, research on improving the interfacial properties of aramid fiber composite materials is a hot topic in the materials industry both domestically and internationally, and is one of the key technological issues that urgently need to be addressed in the application of aramid fiber composite materials. Modifying the surface of aramid fibers has become an important way to improve the interfacial properties of composite materials.

Plasma is used to clean dirt on the surface of objects. Due to the fact that the medium required for plasma cleaning is generally composed of hydrogen, oxygen, hydrogen, etc., and the products generated after cleaning are mostly non polluting gases such as CO2 and H2O, compared to wet cleaning processes, it eliminates the drying process and wastewater treatment equipment. Therefore, using it for large-scale surface treatment is an economical and environmentally friendly method. Practice has proven that plasma cleaning technology can effectively solve the problem of substandard coating quality caused by release agents. Whether from the perspective of future production processes or the directness of current production problems, it is necessary to introduce advanced cleaning technology such as plasma cleaning to solve the above problems and improve production processes and quality.

Principle of plasma cleaning

Plasma is a partially ionized gas composed of charged particles such as positive ions, negative ions, and free electrons, as well as uncharged neutral particles such as excited molecules and free radicals. In electronic cleaning, low-pressure gas glow plasma is mainly used. Some non polymeric inorganic gases are excited at high frequency and low pressure, producing various active particles containing ions, excited molecules, and free radicals. These active particles can react with surface materials to achieve the purpose of cleaning.

Under the combined action of oxygen atom radicals, excited oxygen molecules, electrons, and ultraviolet radiation in oxygen plasma, the release agent is ultimately oxidized into water and carbon dioxide molecules, which are removed from the surface of the object. The reactive oxygen species in the plasma undergo oxidation reaction with the release agent on the surface of aramid fiber material. Figure 1 is a schematic diagram of the plasma cleaning process.

Principle of plasma cleaning

In response to the problem of substandard coating quality caused by the presence of release agents on aramid fibers, plasma cleaning technology can effectively remove residual release agents on the surface of aramid fibers and improve surface activity, enhance the adhesion performance between the coating and the substrate, and ensure the reliability of aramid fiber surface coating.