Plasma is a macroscopically electrically neutral ionized gas composed of charged particles (positive ions, negative ions, electrons), photons, and neutral particles (atoms, molecules, free radicals, and active groups). Compared with the usual three states of matter (solid, liquid, and gas), plasma has essential differences in both composition and properties. Therefore, plasma is also known as the fourth state of matter. Plasma contains a large number of active particles, such as high-energy electrons, ions, free radicals, excited gas atoms and molecules, as well as photons, whose energy can act on the surface of materials through collisions between neutral particle and ion streams. These particles interact with the material surface, such as etching and cleaning, oxidation grafting, activation, polymerization, etc., in order to improve the surface properties of materials.

What properties can be significantly improved by plasma treatment of surfaces?

Low temperature plasma treatment can effectively improve the surface properties of polymer materials, including wetting, adhesion, dyeing, printability, anti-static, water repellent, oil repellent, and other properties. Among them, the following are the more common ones with significant performance improvement after plasma treatment.

Improve the hydrophilicity of the material surface

The smaller the surface contact angle of an object, the better its wettability. After plasma treatment, the surface wettability of the material is significantly improved due to the introduction of a large number of oxygen-containing functional groups. Normally, after being treated with gas plasma such as Ar, O2, N2, etc., polymer materials will introduce functional groups such as - COO. H, - C==O, - NH2 on the surface to increase surface hydrophilicity.

Improve the adhesion between materials

Many polymer materials such as polymer films and fibers exhibit low adhesion due to their low surface energy, making them difficult to be wetted by solvents. After plasma treatment, polymer materials are prone to introducing polar groups or active sites on their surfaces, increasing surface activity and surface energy, transforming non-polar surfaces into polar surfaces, enhancing the van der Waals forces between the bonding material and the binder, and thus achieving the goal of improving material adhesion.

Improve the biocompatibility of materials

The reaction of organisms to biomedical materials is mainly determined by the chemical composition and molecular structure of the material surface. This also requires the material surface to have a certain degree of biocompatibility. Low temperature plasma technology can effectively introduce new functional groups or change the surface chemical structure of polymer materials, thereby improving the biocompatibility of polymer materials, and has wide applications in the biomedical field.

Improve printing performance

Electrons or ions in the plasma hitting the surface of the substrate can, on the one hand, open up the long molecular chains of the material and produce high-energy functional groups; On the other hand, the impact can cause small pinholes to appear on the surface of the material, and also lead to the dissociation and re dissociation of surface impurities. The ozone released during ionization has strong oxidizing properties, and the attached impurities are oxidized and removed, increasing the surface free energy of the substrate and achieving the goal of improving printing performance.

Improve staining quality

The improvement of hydrophilicity in textiles is extremely beneficial for fabric dyeing, as it can promote the penetration rate and uniformity of the dye solution, and increase the dye uptake rate.

The above is an introduction to which properties can be significantly improved by plasma treatment. Low temperature plasma treatment is easy to operate, safe and pollution-free, with short treatment time and high efficiency. It only modifies the surface of materials without changing their intrinsic properties. Therefore, it has important application value in surface modification of materials such as films and fibers. However, plasma technology still has shortcomings in the process of material surface modification, mainly due to the small number and volume of polar groups introduced on the material surface, which are prone to rearrangement, rotation, or burial below the material surface, rendering the chemical etching obtained on the surface ineffective. That is, plasma treatment has timeliness, which limits its practical application in production.