Properties of perfluoropolyether greases Perfluoropolyethers are low molecular weight fluoropolymers, and their viscosity is closely related to molecular structure and average molecular weight. Higher molecular weight PFPEs have low volatility, wide liquid temperature ranges, and excellent viscosity-temperature characteristics. Perfluoropolyether molecules only contain three elements, C, F, and O. Due to the strong electronegativity of fluorine atoms, most of the carbon chain is shielded by fluorine atoms. Compared with hydrocarbon polyethers, it has high density and surface tension. Low volatility, good viscous flow, non-flammability, good dielectric properties, good lubricity, etc., and can be well compatible with plastics, rubber, and metals.
The chemical composition and structure of perfluoropolyether determine that perfluoropolyether has excellent chemical properties, and because the chemical structures of various perfluoropolyethers are relatively close, they also have similar chemical properties. 1) Chemically inert Perfluoropolyethers show strong chemical inertness to most corrosive chemicals such as acids, bases and oxidants, but some nucleophiles (such as ammonia), active metals (such as Na, K, Al, etc.) and Lewis acids It can decompose perfluoropolyether and reduce its thermal stability.
2) Thermal oxidation stability In the absence of effective catalysts, even in the presence of oxygen, perfluoropolyethers are stable in the range of 270-300. Its decomposition temperature can reach 350-410. The presence of certain catalysts or inhibitors will change the thermal stability limit and degradation rate of perfluoropolyethers. In the presence of oxygen and some metals (or metal oxides, fluorides), the degradation temperature of perfluoropolyether generally drops by about 50%. At the same time, generally linear polyethers have better thermal oxidation resistance than those with branched structures. The use of stabilizers (such as aromatic amines, benzimidazole derivatives and selenides) can prevent or improve the effect of metals on perfluoropolyether oils at high temperatures.
3) Compatibility Perfluoropolyether is compatible with many substances, such as oxidants (hydrogen peroxide, liquid oxygen, etc.), hydrocarbon fuels, unsymmetrical dimethylhydrazine, diethyltriamine, etc. Y-type and Z-type perfluoropolyether have good compatibility with plastics and artificial rubber.
4) Fire resistance Flame resistance is an important condition for perfluoropolyethers to be suitable for industrial and aviation lubricants. Compared with other types of lubricants, perfluoropolyethers are more suitable for high temperature and harsh operating environments.
5) Radiation resistance Perfluoropolyether has better radiation resistance, and at the same dose, the viscosity growth rate is the lowest compared with hydrocarbons and silicone oils.
Application field Perfluoropolyether materials are mainly used in special lubricants, industrial fluids, functional chemicals, etc. The specific application areas are: 1) Aerospace industry PFPE is suitable for lubricating and lubricating power systems and mechanical systems exposed to space such as engines, propeller bearings, rudder adjusters, power wheels, scanning mirrors, gear pumps, pressure gauges, metal joints and threaded fasteners, etc. seal.
2) Nuclear Industry Perfluoropolyether is suitable for bearing lubrication of ultracentrifuges in nuclear industry facilities, and is the only material that can resist the corrosion of uranium hexafluoride under 130.
3) Electronic and electrical industry Perfluoropolyethers are suitable for the lubrication of mechanical vacuum pumps in various semiconductor chip production processes such as plasma etching, chemical vapor deposition and ion implantation, and as lubricants on hard disks, magnetic disks and other magnetic recording media in electronic instruments .
4) Chemical industry Perfluoropolyether can be used as the working fluid medium of various vacuum pumps (such as rotary pumps, turbomolecular pumps, vapor diffusion pumps) (especially in the presence of corrosive gases), and also used for contact with liquid oxygen, oxygen, corrosion and Lubricating material for compressors and valves for oxidizing gases.
5) Other industries Perfluoropolyether is also widely used in oxygen production industry, electromechanical industry, mold, automobile industry and mechanical lubrication under high temperature, high load and high corrosion under various extreme working conditions.
