What are the PTFE surface treatment methods?

Chemical treatment chemical treatment of fluorine-containing materials, mainly through the chemical reaction of the etching solution with PTFE, tearing off some of the fluorine atoms on the surface of the material, leaving a carbonized layer and some polar groups on the surface. Infrared spectroscopy shows that in PTFE The introduction of polar groups such as hydroxyl groups, carbonyl groups and unsaturated bonds on the surface can increase the surface energy, reduce the contact angle, improve the wettability, and change from difficult to sticky. This is the current surface treatment method. The effect is better, and it is also the more common method. However, there are some disadvantages: the surface of the adherend is darkened or blackened, the surface resistance is lowered under high temperature environment, and the bonding performance is greatly reduced under long-term exposure to light. These disadvantages make The application of this method is greatly limited. Generally, sodium naphthalene tetrahydrofuran is used as an etching solution, and sodium biphenyldioxane, sodium naphthalene glycol dimethyl ether or the like can also be used as an etching solution. In addition, the method cannot be used for PTFE as needed. The surface is selectively modified to have a certain degree of blindness, which is very disadvantageous in practical applications.
The high-temperature melting method changes the crystal morphology of the PTFE surface at a high temperature, and embeds some materials with high surface energy and easy adhesion, such as SiO2, Al powder, etc., after cooling, a layer of viscous material is formed on the surface of the PTFE. Modified layer. Since the molecules of the easy-adhesive substance have entered the surface layer of the PTFE micropowder , the bonding strength is very high. The advantage of this method is weather resistance, heat and humidity resistance is remarkable compared with other methods, and is suitable for long-term outdoor use. It is a toxic substance, perfluoroisobutylene, which is released during high temperature sintering and is not easy to maintain shape.
The PTFE micropowder is placed in a polymerizable monomer such as styrene, fumaric acid or methacrylate, and the monomer is chemically graft polymerized on the surface of the PTFE by 60Co radiation, thereby forming a layer on the surface of the PTFE to be easily adhered. Grafted polymer. After grafting, the surface becomes rough, the bonding surface area is increased, and the bonding strength is improved. The advantage of this method is simple operation, short processing time and high speed, but the modified PTFE surface is lost. Some have a smooth feel and luster, and the 60Co radiation source is more harmful to the human body.
Low-temperature plasma refers to an ionized gas generated by low-pressure discharge (glow, corona, high-frequency, microwave). Under the action of an electric field, free electrons in a gas obtain energy from an electric field into high-energy electrons, which are high-energy electrons and gases. In the atom, the collision of molecules, if the energy of the electron is greater than the excitation energy of the molecule or atom, it can generate the excitation molecule and the excitation atom, the radical, the ion and the radiation with different energy. The active particle in the low temperature plasma has the energy Close or exceed the bond energy of a carbon-carbon bond or other carbon-containing bond, and thus can chemically or physically interact with the gas or solid surface of the introduction system. If a reactive oxygen plasma is used, it can occur with the polymer surface. Chemical reaction introduces a large number of oxygen-containing groups, which makes the surface molecular chain polar, surface tension is obviously improved, and surface activity changes. Even if non-reactive Ar plasma is used, it can be caused by surface crosslinking and etching. Surface physical changes significantly improve the contact angle and surface energy of the polymer surface.
The use of ArF as a laser for the treatment of PTFE is a new method adopted abroad. Its basic principle is to irradiate a substance with a laser. On the one hand, it can react with the surface of the PTFE to introduce a substance that is easy to bond; On the one hand, the surface of the PTFE can form free radicals, and the monomer can form a graft copolymer with it to achieve the purpose of improving the bonding strength. According to the reaction type, it can be divided into a group reaction and a graft reaction.