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What are the characteristics of polyfluoroethylene propylene (FEP)

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What are the characteristics of polyfluoroethylene propylene (FEP)

  • Categories:Industry news
  • Author:PFA tube lady
  • Origin:PFA tube lady
  • Time of issue:2019-08-26 10:04
  • Views:

What are the characteristics of polyfluoroethylene propylene (FEP)

  • Categories:Industry news
  • Author:PFA tube lady
  • Origin:PFA tube lady
  • Time of issue:2019-08-26 10:04
  • Views:

  What are the characteristics of polyfluoroethylene propylene (FEP)

  English name: FEP (Fluorinated ethylene propylene)

  FEP is a copolymer of tetrafluoroethylene and hexafluoropropylene. The content of hexafluoropropylene is about 15%. It is a modified material of polytetrafluoroethylene. Full name: fluorinated ethylene propylene copolymer (perfluoroethylene propylene copolymer), abbreviated as polyperfluoroethylene propylene, also abbreviated as F46.

  FEP has a crystalline melting point of 580°F and a density of 2.15g/CC (grams per cubic centimeter). It is a soft plastic with lower tensile strength, wear resistance and creep resistance than many engineering plastics. It is chemically inert and has a low dielectric constant, about 2.1, over a wide temperature and frequency range. The material does not ignite and can prevent the spread of flames. It has excellent weather resistance, low friction coefficient, and can be used from low temperatures to 392°F. The material can be made into granular products for extrusion and molding, used as powder for fluidized bed and electrostatic coating, and can also be made into water dispersion. Semi-finished products include films and plates. Rod and single fiber.

  FEPs distributed in the US market include the Teflon brand of DUIPont, the Neoflo brand of Daikin, and the IHoustaflow brand of Hoechst Celanese. Its main purpose is to make the inner layer of pipes and chemical equipment, the surface of the drum, and various wires and cables, such as aircraft hook wires, booster cables, alarm cables, flat cables and oil well logging cables. FEP film has been used as a thin coating for solar collectors.

  F46 resin not only has similar characteristics to PTFE, but also has good processing properties of thermoplastics. Therefore, it makes up for the deficiencies of the difficult processing of PTFE, making it a material to replace PTFE, and is widely used in the production of wires and cables for electronic equipment transmission wires used under high temperature and high frequency, connecting wires inside electronic computers, Insulation layer of aerospace wires and special purpose installation wires, oil pump cables and winding wires of submersible motors.

  According to processing needs, F46 can be divided into three types: pellets, dispersions and paints. Among them, the pellets can be used for molding, extrusion and injection molding according to their melt index; the dispersion is used for dipping and sintering; the paint is used for spraying.

  1. Structural characteristics of polyperfluoroethylene propylene

  F46 resin, like polytetrafluoroethylene, is also a fully fluorinated structure. The difference is that part of the fluorine atoms in the main chain of F46 are replaced by trifluoromethyl (-CF3).

  It can be seen that although both F46 resin and polytetrafluoroethylene are composed of fluorocarbon elements, the carbon chain is completely surrounded by fluorine atoms, but F46 has branches and side chains on the main chain of its macromolecule. This structural difference has no significant effect on the upper limit of the temperature range of the material under long-term stress. The upper limit temperature of F46 is 200°C, while the maximum use temperature of PTFE is 260°C. However, this difference in structure makes F46 resin have a fairly definite melting point, and can be molded and processed by general thermoplastic processing methods, greatly simplifying the processing technology. This is not available in PTFE. This is the main purpose of modifying polytetrafluoroethylene with hexafluoropropylene.

  2. The performance of polyperfluoroethylene propylene

  The content of hexafluoropropylene in F46 has a certain influence on the performance of the copolymer. The content of hexafluoropropylene in F46 resin currently produced is usually about 14% to 15% (mass fraction).

  2.1. Physical properties

  There is currently no feasible method for determining the molecular weight of F46 resin. But its melt viscosity at 380℃ is lower than that of PTFE, which is 103~104Pa.s. It can be seen that the molecular weight of F46 is much lower than that of polytetrafluoroethylene.

  The melting point of F46 varies with the composition of the copolymer. When the content of hexafluoropropylene in the copolymer increases, the melting point becomes lower. According to the results measured by the differential thermal analysis method, the melting point of domestic F46 resin is mostly between 250 and 270 ℃, which is lower than that of PTFE.

  F46 resin is a kind of crystalline high polymer, the crystallinity is lower than that of polytetrafluoroethylene. When the F46 melt is slowly cooled to a temperature below the crystal melting point, the macromolecules recrystallize, and the crystallinity is between 50% and 60%; When the melt is rapidly cooled by quenching, the crystallinity is small, between 40% and 50%. The crystal structure of F46 is a spherulite structure, and there are certain differences depending on the resin, the processing temperature and the heat treatment method.

  2.2. Electrical insulation properties

  The electrical insulation performance of F46 is very similar to that of PTFE. Its dielectric coefficient is almost constant from deep cold to the highest operating temperature, from 50Hz to 1010Hz in a wide range of ultra-high frequency, and it is very low, only about 2.1. The dielectric loss tangent changes slightly with frequency, but does not change much with temperature.

  The volume resistivity of F46 resin is very high, generally greater than 1015Ω.m, and changes little with temperature, and it is not affected by water and moisture. Arc resistance is greater than 165s.

  The breakdown field of F46 increases as the thickness decreases. When the thickness is greater than 1mm, the breakdown field strength is above 30KV/mm, but it does not change with temperature.

  2.3. Thermal performance

  The heat resistance of F46 resin is second only to PTFE, and it can be used continuously in the temperature range of -85~+200℃. Even in the extreme conditions of -200°C and +260°C, its performance does not deteriorate, and it can be used for a short time.

  The thermal decomposition temperature of F46 resin is higher than the melting point temperature, and significant thermal decomposition occurs above 400°C. The decomposition products are mainly tetrafluoroethylene and hexafluoropropylene. Because F46 macromolecules usually have equal end groups that will decompose at temperatures above the melting point, proper ventilation must also be paid when processing at temperatures above 300°C. F46 is quite stable below the melting point temperature, but the mechanical strength loss is greater at a high temperature of 200°C. The increase in melt index can be used to analyze the decrease in melt viscosity and the thermal decomposition of the copolymer.

  F46 is still not completely hard and brittle at -250°C, and it still maintains a small elongation and a certain degree of flexibility. It is even better than PTFE, and it is inferior to all other types of plastics.

  2.4. Chemical resistance

  The chemical resistance of F46 is similar to that of polytetrafluoroethylene, and it has excellent chemical resistance. Except for reacting with fluorine element, molten alkali metal and chlorine trifluoride at high temperature, it will not be corroded when it comes in contact with other chemicals.

  2.5. Mechanical properties

  Compared with PTFE, F46 has slightly improved hardness and tensile strength, and the coefficient of friction is also slightly larger than that of PTFE. At room temperature, F46 has better creep resistance; but when the temperature is higher than 100°C, the creep resistance is inferior to that of PTFE.

  2.6. Other properties

  F46 resin has very good oxidation resistance in the atmosphere and high atmospheric stability. The radiation resistance of F46 is better than PTFE and slightly inferior to polyethylene. In the air and at room temperature, the minimum absorbed dose at which F46 begins to change performance is 105-106rad (that is, 103-104Gy), so it can be used as a radiation-resistant material.

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