Why is the stability of perfluoropolyether lubricating grease so good?
July 26, 2023
Characteristics of perfluoropolyether lubricating grease Perfluoropolyether belongs to low molecular weight fluoropolymer, and their viscosity has a great relationship with molecular structure and average molecular weight. PFPE with larger molecular weight has low volatility, a wide liquid temperature range, and excellent viscosity temperature characteristics. The perfluoropolyether molecule contains only three elements, C, F and O. Due to the strong Electronegativity of the fluorine atom, most of the carbon chain is shielded by the fluorine atom. Compared with the hydrocarbon polyether, the perfluoropolyether has the advantages of high density, low surface tension, low volatility, good viscosity, incombustibility, good dielectric properties, good lubrication, etc., and is well compatible with plastics, rubber, and metals. The chemical composition and structure of perfluoropolyether determine that perfluoropolyether has excellent chemical properties. At the same time, due to the close chemical structures of various perfluoropolyether, they also have similar chemical properties.
1) Chemical inertness Perfluoropolyether exhibits strong chemical inertness towards most corrosive chemicals such as acids, bases, and oxidants. However, some nucleophilic reagents (such as ammonia), active metals (such as Na, K, Al, etc.), and Lewis acid can cause the decomposition of perfluoropolyether, reducing its thermal stability. 2) Thermal oxidation stability In the absence of an effective catalyst, perfluoropolyether remains stable in the range of 270-300 even in the presence of oxygen. Its decomposition temperature can reach 350-410. The presence of certain catalysts or inhibitors can alter the thermal stability limit and degradation rate of perfluoropolyether. When there is oxygen and some metals (or metal oxides, fluorides) present, the degradation temperature of perfluoropolyether generally decreases by about 50. Meanwhile, straight chain polyethers generally have better thermal oxidation resistance than those with branched chain structures. The use of stabilizers (such as aromatic amines, Benzimidazole derivatives and Selenide) can prevent or improve the impact of metals on perfluoropolyether oil at high temperatures. 3) Compatibility Perfluoropolyether is compatible with many substances, such as oxidants (hydrogen peroxide, liquid oxygen, etc.), hydrocarbon fuels, Unsymmetrical dimethylhydrazine, diethyl triamine, etc. Y-type and Z-type perfluoropolyether structures have good compatibility with plastics and artificial rubber. 4) Flame resistance Flame resistance is an important condition for perfluoropolyether to be suitable for industrial and aviation lubricants. Compared with other types of lubricants, perfluoropolyether is more suitable for high-temperature and harsh operating environments. 5) Radiation resistance Perfluoropolyether has good radiation resistance and has the lowest viscosity growth rate compared to hydrocarbons and silicone oil at the same dosage. Application area Perfluoropolyether materials are mainly used in special lubricants, industrial fluids, functional chemicals, etc. The specific application fields include: 1) Aerospace Industry Perfluoropolyether is suitable for lubrication and sealing of power systems and mechanical systems exposed to space, such as engines, thruster bearings, rudder adjusters, power wheels, scanning mirrors, gear pumps, pressure gauges, metal joints, and threaded fasteners. 2) Nuclear industry Perfluoropolyether is suitable for bearing lubrication of ultracentrifuges in nuclear industry facilities, and is the only material that can resist Uranium hexafluoride corrosion at 130 ℃.
3) Electronic and Electrical Industry
Perfluoropolyether is suitable for lubrication of mechanical vacuum pumps in various semiconductor integrated block production processes such as plasma etching, chemical vapor deposition, and ion value injection. It can also be used as a lubricant on hard drives, magnetic disks, and other magnetic recording media in electronic instruments.
4) Chemical industry
Perfluoropolyether can be used as a working fluid medium for various vacuum pumps (such as rotary pumps, turbomolecular pumps, steam diffusion pumps), especially in environments with corrosive gases, and as a lubricating material for compressors and valves in contact with liquid oxygen, oxygen, corrosive and oxidizing gases.
5) Other industries
Perfluoropolyether is also widely used in the fields of oxygen production, electromechanical industry, mold, automotive industry, and mechanical lubrication under various extreme operating conditions of high temperature, high load, and high corrosion.
