Overview
Perfluoropolyether (PFPE, English name Perfluom Polyethers) is a special kind of perfluorinated polymer compound, its average molecular weight ranges from 500 to 15,000, and there are only three elements of C, F, and O in the molecule, which has heat resistance. , Oxidation resistance, radiation resistance, corrosion resistance, non-combustibility and other characteristics, widely used in chemical industry, electronics, electrical appliances, machinery, nuclear industry, aerospace fields.
Resolve resolution
According to the different monomers and polymerization methods used, PFPE with different molecular structures of K type, Y type, Z type and D type can be obtained:
1. The first K-type structural formula is: CF3CF2CF2O[CF(CF3)CF2O]nCF(CF3)COF, which is a series of branched chain polymers formed by polymerization of hexafluoropropylene oxide (HFPO) under the catalysis of CsF.
2. The second Y-type structural formula is CF3O(C3F6O)m(CF2O)nCF3, which is a polymer formed by photooxidation of hexafluoropropylene (HFP) under the action of ultraviolet light, and its molecular weight is generally between 1000 and 10000.
3. The third Z-type structural formula is: CF3(C2F4O)m(CF2O)nCF3, which is a linear polymer formed by photooxidation of tetrafluoroethylene (TFE) under ultraviolet light irradiation, and its molecular weight is generally between 1,000 and 100,000. between.
4. The fourth type D structural formula is: C3F7O(CF2CF2CF2O)mC2F5, which is a polymer obtained by directly fluorinating the polymerization product of tetrafluorooxetane.
Characteristic
Perfluoropolyether molecules only contain three elements, C, F, and O. Due to the strong electronegativity of fluorine atoms, most of the carbon chains are shielded by fluorine atoms, and the C-O and C-F bonds are very stable.
The chemical composition and structure of perfluoropolyether determine that perfluoropolyether has excellent physical and chemical properties:
1. Chemical inertness
Perfluoropolyether shows strong chemical inertness to most corrosive chemicals such as acids, alkalis 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. Thermo-oxidative stability
In the absence of an effective catalyst, even in the presence of oxygen, perfluoropolyether is still very stable in the range of 270-300. Its decomposition temperature can reach 350-410°C. The presence of certain catalysts or inhibitors will change the thermal stability limit and degradation rate of perfluoropolyether. 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 straight-chain polyethers have better thermal oxidation resistance than those with branched chain structures. The use of stabilizers (such as aromatic amines, benzimidazole derivatives and selenides) can prevent or improve the impact of metals on perfluoropolyether oils at high temperatures.
3.Viscosity properties
The viscosity index of perfluoropolyether oil is 150-400 (the oil with larger molecular weight has a larger viscosity index), which has great advantages compared with mineral oil.
4.Lubricating properties
Perfluoropolyether oil has low friction coefficient, high load resistance and good lubricity.
5.Vapor Pressure-Temperature Characteristics
The perfluoropolyether oil has a large molecular weight and a low pour point, and the lubricating oil shows a very low vapor pressure from low temperature to high temperature.
6.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 perfluoropolyethers have good compatibility with plastics and artificial rubber.
7.Flame resistance
Flame resistance is an important requirement for perfluoropolyethers to be used in industrial and aerospace lubricants. Compared with other types of lubricants, perfluoropolyethers are more suitable for high temperature and harsh operating environments.
8.Radiation resistance
Perfluoropolyether has better radiation resistance, and has the lowest viscosity growth rate compared with hydrocarbons and silicone oils at the same dose.
