What are the FEP characteristics of polyfluoroethylene propylene (FEP)?

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

FEP TUBE has a crystalline melting point of 580 °F and a density of 2.15 g/cc (g/cm3). It is a soft plastic with lower tensile strength, abrasion resistance and creep resistance than many engineering plastics. It is chemically inert and has a low dielectric constant over a wide temperature and frequency range of about 2.1. This material does not ignite and prevents the spread of the flame. It has excellent weatherability and a low coefficient of friction, from low temperatures to 392 °F. The material can be made into a granular product for extrusion and molding, used as a fluidized bed and electrostatically coated powder, or as an aqueous dispersion. Semi-finished products have membranes and plates. Rods and single fibers.

The FEP TUBE distributed in the US market include Teflon from DUIPont, Neofro from Daikin, and IHoustaflow from Hoechst Celanese. Its main uses are in the production of tubes and chemical equipment for the inner village, the surface of the drum and various wires and cables, such as aircraft hook lines, pressurized cables, alarm cables, flat cables and oil well logging cables. FEP membranes have been found to be used as thin coatings for solar collectors.

F46 TUBE resin has both similar properties to Teflon and good processing properties of thermoplastics. Therefore, it makes up for the difficulty of processing PTFE, making it a material to replace PTFE. It is widely used in wire and cable production for transmission lines of electronic equipment used in high temperature and high frequency, connecting wires inside electronic computers, Insulation of aerospace wires and their special purpose installation lines, oil pump cables and submersible motor winding wires.

According to the processing needs, F46 can be divided into three kinds of pellets, dispersions and paints. Among them, the pellets can be used for molding, extrusion and injection molding according to their different melt indexes; the dispersion is used for impregnation and sintering; the paint is used for spraying and the like.

  1. FEP TUBE Structural characteristics of polyperfluoroethylene propylene

Like the polytetrafluoroethylene, the F46 resin is also a completely fluorinated structure, except that part of the fluorine atom of the F46 main chain is replaced by a trifluoromethyl group (-CF3).

It can be seen that although 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 its main chain. This structural difference does not have a large 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, and the maximum use temperature of polytetrafluoroethylene is 260 ° C. However, this structural difference allows the F46 resin to have a fairly defined melting point and can be formed by a general thermoplastic processing method, which greatly simplifies the processing. This is not available in Teflon. This is the main purpose of modifying polytetrafluoroethylene with hexafluoropropylene. Properties of polyperfluoroethylene propylene

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

2.1.FEP TUBE Physical properties

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

The melting point of F46 varies depending on the composition of the copolymer. When the content of hexafluoropropylene in the copolymer increases, the melting point becomes low. According to the results measured by differential thermal analysis, the melting point of domestic F46 resin is mostly between 250 and 270 ° C, which is lower than that of polytetrafluoroethylene.

F46 resin is a crystalline polymer with a lower crystallinity than polytetrafluoroethylene. When the F46 melt is slowly cooled to a temperature below the melting point of the crystal, the macromolecules are recrystallized 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 spherulitic structure, and it has certain differences depending on the resin and processing temperature and heat treatment method.

2.2. FEP TUBE Electrical insulation properties

The electrical insulation properties of F46 are very similar to those of PTFE. Its dielectric constant ranges from cryogenic to maximum operating temperature, from 50Hz to 1010Hz. The UHF range is almost constant and is very low, only around 2.1. The dielectric loss tangent varies somewhat with frequency, but does not change much with temperature.

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

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

2.3. FEP TUBE Thermal performance

The heat resistance of F46 resin is second only to PTFE and can be used continuously in the temperature range of -85 to +200 °C. Even at the limit of -200 ° C and +260 ° C, its performance does not deteriorate and 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. Since the equipotential group usually contained in the F46 macromolecule also decomposes at a temperature above the melting point, proper ventilation must also be taken when processing at temperatures above 300 °C. F46 is fairly stable below the melting point, but at a high temperature of 200 °C, the mechanical strength loss is large. The increase in the 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, but also maintains a small elongation and a certain degree of flexibility, even better than Teflon, which is beyond the reach of all other types of plastics.

2.4. FEP TUBE Chemical resistance properties

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

2.5. FEP TUBE Mechanical properties

Compared with PTFE, F46 has slightly improved hardness and tensile strength, and the friction coefficient is slightly larger than that of polytetrafluoroethylene. At room temperature, F46 has good creep resistance; but when the temperature is higher than 100 °C, the creep resistance is not as good as that of polytetrafluoroethylene.

2.6. FEP TUBE Other performance

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