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Application of low friction performance of PTFE gasket
PTFE gaskets are not recommended for lubrication due to the potential issues caused by friction in certain equipment. For example, in environments where lubricants may be dissolved by solvents, or in industries like paper, pharmaceuticals, food, and textiles, it is crucial to avoid any contamination from lubricants. This makes PTFE an ideal choice for mechanical components that require oil-free operation under direct load. The material’s extremely low friction coefficient sets it apart as one of the most suitable materials for such applications.
PTFE gaskets are known for their excellent overall performance, including high-temperature resistance, corrosion resistance, non-stick properties, self-lubrication, and outstanding electrical insulation. By incorporating fillers that can withstand the sintering temperature of PTFE, its mechanical properties can be significantly enhanced while maintaining its other advantageous characteristics. Common fillers include glass fiber, metal, metal oxides, graphite, molybdenum disulfide, carbon fiber, polyimide, and EKONOL. These additions can increase wear resistance and the limiting PV value by up to 1000 times.
The depolymerization of polytetrafluoroethylene into tetrafluoroethylene requires only 171.38 kJ per mole of energy, making it a relatively stable compound under pyrolysis conditions. At temperatures of 260°C, 370°C, and 420°C, the weight loss rates of Teflon gaskets were recorded as 1 × 10â»â´, 4 × 10â»Â³, and 9 × 10â»Â², respectively. This indicates that PTFE can be used reliably at 260°C for extended periods. However, during thermal decomposition, toxic byproducts such as fluorophosgene and perfluoroisobutylene may form, so proper safety precautions must be taken to prevent contact with open flames.
PTFE gaskets find wide application in bearings for chemical equipment, papermaking machinery, agricultural tools, piston rings, machine tool guides, and guide rings. They are also extensively used in civil engineering projects such as bridges, tunnels, steel roof trusses, and large-scale infrastructure. Additionally, they serve as support slides for storage tanks, bridge supports, and swivel joints.
The chemical stability of PTFE gaskets makes them suitable for use in stuffing boxes, pipe thread sealing tapes, ropes, packings, microporous diaphragms, filter plates, linings, membranes, liquid level floaters, and experimental instruments. They are also used in communication satellites, coaxial transmission lines, ultra-high-frequency communication systems, micro-motor windings, control cables in thermal power plants, and insulation for double-water-cooled pipes and electrolytic cells.
Due to its low friction coefficient, PTFE is non-stick and easy to handle. To improve wear resistance and creep resistance, filled PTFE is commonly used in manufacturing mechanical parts such as sealed bearings, piston rings, rollers, and intake heads.
PTFE gaskets have a low dielectric constant and dielectric loss across a wide frequency range, along with high breakdown voltage, volume resistivity, and arc resistance. It is produced through the radical polymerization of tetrafluoroethylene. Industrial production typically involves stirring in water to manage heat and control temperature, with polymerization occurring between 40°C and 80°C under pressures ranging from 3 to 26 kgf/cm². Inorganic persulfates, organic peroxides, or redox initiation systems may be used as initiators.
Aramid packing is another type of sealing material, suitable for sealing machinery, pumps, valves, pipes, and containers used in fluid conveyance. It offers excellent lubricity, wear resistance, high strength, good chemical resistance, high resilience, low cold flow, and ease of disassembly. It is particularly ideal for dynamic sealing applications involving solid particle media.
Technical parameters for aramid packing include a temperature range of -100°C to +300°C, a pressure rating of 35 MPa, and a pH range of 2 to 13.
Oil-containing PTFE packing is specially treated with low-friction PTFE wire, making it suitable for dynamic sealing in pumps. However, it is generally not recommended for high-speed pump applications. Standard sizes range from 3×3 mm to 50×50 mm, with custom options available upon request. Its technical parameters include a pressure of 10 MPa, a temperature limit of 260°C, a pH range of 0–14, and a linear speed of 10 m/s.
Expanded graphite packing is woven from flexible graphite wire, offering excellent self-lubrication, thermal conductivity, a low friction coefficient, strong versatility, flexibility, and high strength. It provides good protection for the shaft and can be reinforced with carbon or glass fibers based on specific requirements.
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