Although poly Tetrafluoroethylene products It has excellent characteristics, but its defects (such as reducing the difference in resilience, stress relaxation diamond class "cold flow condition") will endanger the sealing characteristics of PTFE, so the modified material teflon The key to scientific research is to further improve its comprehensive performance. At present, the modified materials of polytetrafluoroethylene are mainly composite with other raw materials and filled with the characteristics of polymer materials teflon The key ways to achieve the goal of modified materials are: surface treatment modified materials, filling modified materials, blending modified materials, etc.
1、 Surface treatment modified material: PTFE has very low surface activity and non sticking characteristics, which limits its composite type with other raw materials. The surface modification material of PTFE raw materials is to better improve the surface activity. The technical properties of common PTFE surface modification materials are as follows:
1. Surface activity technicality
(1) Low temperature plasma activation mode. The plasma technology of argon, helium, hydrogen, nitrogen and other vapors is used to solve PTFE raw materials, so as to improve the activation energy of its surface layer, improve its lubricity and adhesion, and generate a surface active layer that can heat connect the surface layer.
(2) Irradiance activity method. The surface layer is defluorinated according to the irradiance of high energy radiation, thus resulting in the actual effect of bonding with other raw materials.
(3) Arc discharge active mode. After moderate flame treatment, in a certain atmosphere, PTFE will produce a hot connected active layer on its surface;
(4) Potassium acetate activity method. PTFE is infiltrated into molten potassium acetate at a special temperature, and after a certain solution time, an active layer with a certain level of activity effect is generated on its surface.
(5) Special solutions can solve the problem of activity. For example, PTFE can improve its surface activity by heating in a certain preparation of sodium hydroxide solution and dipe based polycyandiamide solution for a certain time. There are also some other active solutions, such as Tesla hollow transformer charging and discharging active method, laser myopia surgery active method, etc.
2. Chemical corrosion of surface modified materials
PTFE can also be modified by etching its surface with some compounds. Common surface corrosives are as follows:
(1) Ammonia solution of sodium metal materials. The interfacial tension of PTFE can be reduced from 108 ° to 52 ° after the aqueous solution with a certain concentration is used to solve PTFE, which can be compounded with epoxy resin adhesive for other raw materials.
(2) Sodium naphthalene tetrahydrofuran aqueous solution. The surface modification material can be completed by solving PTFE with a certain concentration of sodium, naphthalene and tetrahydrofuran aqueous solution. There are also some other corrosion, such as alkaline earth metal amalgam etching, acid alkali etching, five carbon based iron etching, etc.
3. Surface stacking modified materials
Infiltrate PTFE into the colloidal solution of some metal materials, nickel hydroxide, so that the colloidal solution particles are stacked on the surface of PTFE, thereby expanding its wetting angle, so as to improve its surface activity. Some of the above methods are key to the surface modification materials of PTFE plastic film, which have both advantages and disadvantages, The key way to expand the application of PTFE plastic film is to effectively use or find new solutions for surface activity.
2、 Filling modified materials
stay teflon Adding different fillers to make PTFE can reasonably improve its characteristics. Common fillers include carbon fiber materials, glass fiber, bronze powder, high-purity graphite, molybdenum disulfide and some polymer fillers.
(1) , carbon fiber material. Carbon fiber materials can improve the physical properties, temperature resistance and friction coefficient of PTFE. Carbon fiber material filling teflon Its thermal expansion coefficient is small, its thermal conductivity is high, and its compression strength, stress relaxation resistance and wear resistance in water are greatly improved.
(2) , glass fiber. Generally charged to teflon The diameter of glass fiber is 10~13 μ m, the average length is 80 μ m, the height diameter is 5~10, and the charging amount is generally 15%~25%. The addition of glass fiber will make its stress relaxation resistance and cold flow resistance significantly improved, and the wear resistance will also be further improved. However, with the increase of glass fiber composition, its tensile strength, elongation and ductility will slowly decrease, and the friction resistance will slowly expand.
