Where can FEP polyperfluoroethylene propylene be used?
FEP is known as Fluorinated ethylene propylene, translated as Fluorinated ethylene propylene copolymer (perfluoroethylene propylene copolymer) English trade name: Teflon* FEP, is a class of chemical substances. FEP is a copolymer of tetrafluoroethylene and hexafluoropropylene. FEP crystallization melting point of 304 ° C, the density of 2.15g/CC (grams / cubic centimeter). cubic centimeter).
FEP can be applied to soft plastics and has lower tensile strength, abrasion resistance, and creep resistance than many engineering plastics. It is chemically inert and has a low dielectric constant (2.1) over a wide range of temperatures and frequencies.
FEP Properties
The material does not ignite and prevents the spread of flame. It has excellent weatherability, a low coefficient of friction, and can be used from low temperatures to 392F. The material can be made into granular products for extrusion and molding, as a powder for fluidized bed and electrostatic finishing, and as an aqueous dispersion. Semi-finished products are available as films, sheets, rods and single fibers.
FEP Applications
Its main uses are in the lining of tubes and chemical equipment, the top layer of rollers and various wires and cables, such as aircraft hook-up wires, booster cables, alarm cables, flat cables and oil well logging cables.FEP membranes have been seen used as thin coatings for solar collectors.
Polyperfluoroethylene propylene FEP or F46, a copolymer of tetrafluoroethylene and hexafluoropropylene, with about 15% hexafluoropropylene, is a modified material of polytetrafluoroethylene.
F-46 resin has both similar properties to PTFE and the good processing performance of thermoplastics. Therefore, it makes up for the lack of PTFE processing difficulties, so that it becomes a substitute for PTFE materials in the production of wire and cable is widely used in high-temperature and high-frequency use of electronic equipment transmission lines, electronic computers within the connecting line, aviation and cosmic wires and their special-purpose installation lines, oil pump cables and submerged oil motor winding line of the insulating layer.
Production process points
1) feed: F-46 extrusion before the first pre-drying at 120 ℃ for about 3h is appropriate.
2) conductive core preheating: In order to ensure that the extrusion of F-46 insulation layer inside and outside the temperature is uniform, conductive core should be preheated to 300-350 ℃.
3) Extruder temperature distribution: Extruder generally 280 ℃ (feed port) to 380 ℃ (head) linear rise in temperature distribution is good; head temperature fluctuations of not more than ± 5 ℃, and should not lead to the decomposition of the resin under the premise of trying to improve the head temperature, in order to reduce the melt viscosity of the resin. Extruder body (from the feed port to the head), the head, the reference temperature of the mold sleeve as follows.
The first section of the machine body 280-310°C, the second section 315-330°C
The third section 340-360℃, the fourth section 360-380℃.
Machine head 380 ℃ mold sleeve 380-410 ℃
4)The tensile ratio of the die set: it is suitable to choose in the range of 50-200.
5) screw speed: the synergistic temperature of the screw speed adjusted, in the F-46 resin extrusion process, do not change frequently, if necessary, can be slightly adjusted. Screw speed should vary with the size of the conductive core cross-section, generally 5-15r/min.
6) mold die mouth insulation: insulation area should be covered throughout the stretching area, insulation temperature at 350-380 ℃, in order to avoid F-46 cone to the molding before the formation of stress due to the surface of the sudden cold, resulting in insulation cracking.
7) insulated wire cooling: from the extruder after the extrusion of the wire using water cooling. The distance between the mold opening and the water tank is preferred to be closer, and is recommended to be no more than 20cm.
8) Setting the screen. In order to improve the plasticizing and mixing quality of F-46 resin and increase the counterpressure, the end of the extruder screw should be added with 2-3 layers of screen is appropriate.
9) Each batch of F-46 material should strive to the best situation of extrusion, to ensure good plasticization, cone translucent, no bubbles, smooth surface, cone and die between the sleeve without “eye droppings”. Each batch of material to do a good job of process records, in order to accumulate information and process data, conducive to quality analysis.
F-46 insulated wire in the resin quality and extrusion process is not good, the insulation layer will occur cracking phenomenon, the main reasons are.
(a) the insulation layer has internal stress. There are many reasons for the production of internal stress, such as poor plasticization caused by uneven composition of the resin during processing and improper processing techniques.
(b) insulation in the large ball crystal, lamellar crystal interface contact molecular chain is small, or ball crystal is too large, fragile
(c) unstable groups produced by the large molecules of the broken chain
(d)The molecular weight of the resin is too small or the distribution is too wide, so that the material to withstand a reduction in strength.
(e)The content of hexafluoropropylene is too low and the composition is not uniformly distributed.