Polytetrafluoroethylene (PTFE) is a plastic with excellent comprehensive properties, including good chemical stability, heat resistance, cold resistance, and chemical corrosion resistance. It also has high mechanical properties and has been widely used in various fields such as aerospace, petrochemicals, machinery, electronics, construction, and textiles. However, due to the highly symmetrical structure of polytetrafluoroethylene (PTFE) material, which does not contain active groups, has low surface energy, and is not easily wetted, its application in industrial fields such as medical and health is greatly limited. With the continuous expansion of the application scope of polytetrafluoroethylene (PTFE), researchers at home and abroad have conducted extensive research on the surface modification of PTFE, including chemical treatment, functional monomer polymerization, plasma surface treatment, sputtering, etc. These processing methods can effectively improve its adhesion and wettability, increase surface energy, and thus improve hydrophilicity.

Plasma surface treatment

Plasma is composed of a large number of electrons, ions, and neutral particles. These particles act on the surface of the material, causing changes in its structure, composition, and properties. At present, the main methods for modifying polymer materials include plasma modification, irradiation grafting modification, surface chemical modification, etc. However, due to the unique advantages of plasma technology, such as short time and high efficiency; There are no strict requirements for the materials being processed, and they have universal adaptability; Having a high energy density and the ability to generate active ingredients, it can quickly and efficiently induce physical and chemical changes that cannot or are difficult to achieve under normal conditions; The effect on the surface of the material only involves a few to a few hundred nanometers, and while the surface properties of the material are improved, the matrix properties are not affected; It can endow modified surfaces with various excellent properties, without generating a large amount of by-products and waste, and without environmental pollution. The use of plasma surface treatment technology for surface modification of polytetrafluoroethylene (PTFE) materials has gradually become one of the important methods of modification.

Principle of plasma surface treatment of polytetrafluoroethylene (PTFE)

There are many types of particles in plasma, and their properties are also different. The energy of plasma is generally several to tens of electron volts, which is sufficient to break the molecular bonds in polytetrafluoroethylene (PTFE), causing a series of changes such as etching and cross-linking. This type of reaction generally has the following aspects:

(1) Etching: High energy particles bombard the surface of polytetrafluoroethylene (PTFE) material, causing some bonds to break and the material surface to become uneven, which to some extent helps to improve certain surface properties of PTFE.

(2) Free radicals: During plasma treatment, a large amount of free radicals are generated, which cause etching, cross-linking, and chemical modification of the surface of polytetrafluoroethylene (PTFE).

(3) Crosslinking: Free radicals generated during plasma treatment combine again to form a dense cross-linked layer on the surface, while cracking occurs, ultimately reaching dynamic equilibrium during plasma treatment. The formation of cross-linking layer is beneficial for improving the hydrophilicity and adhesion of polytetrafluoroethylene (PTFE) surface.

(4) Polar groups: When polytetrafluoroethylene (PTFE) treated with gas plasma such as O2, Ar, N2, H2, NH3, etc. comes into contact with air, long-life active free radicals on the polymer surface will introduce oxygen-containing or nitrogen-containing polar groups on its surface. Thereby altering the surface properties of polytetrafluoroethylene (PTFE).

The surface energy of PTFE treated with plasma is actually lower than many common polyolefins, such as polyethylene and polypropylene, and is completely within the wettability range required for many adhesives to form strong bonds.

Plasma surface treatment technology is a modification method that uses ion bombardment or implantation on the surface of polytetrafluoroethylene (PTFE) to break the C-F and C-C bonds, generate a large number of free radicals, and introduce active groups to increase the surface free energy of PTFE and improve its wetting and bonding properties. The advantages of simplicity, speed, dry process, and modification only involving the material surface without affecting the structure and properties of the body are increasingly being valued by people.