Plasma treatment is a modification method that has attracted considerable attention from researchers. Plasma is an ionized mixture containing ions, electrons, free radicals, and excited molecules and atoms, which interacts with the fiber surface to produce highly reactive substances. Depending on the properties of the gas used, free radicals, ions, and metastable substances may be generated, initiating ablation, cross-linking, or oxidation reactions. Typical gases used to generate plasma include air, O2, NH3, N2, and Ar.
During the plasma treatment process, the plasma etches and alters the surface morphology of the fiber, thereby increasing its roughness. Oxidation generates oxygen-containing active functional groups, increasing the activity of the fiber surface. This enhances the physical intercalation and chemical bonding between the fiber and the polymer, strengthening the interfacial adhesion. Using mild plasma to treat materials has two main advantages: first, it can be used in any atmosphere, such as inert, reducing, or oxidizing atmospheres; second, the reaction occurs only on the material surface and does not significantly alter the overall properties. This treatment method is simple to operate, highly efficient, causes minimal damage to the fiber, and requires no subsequent treatment. However, it has a time-sensitive nature; the carbon fibers treated in plasma need to be composited with the polymer matrix as soon as possible.
