I. Overview of PFA materials

PFA, full name Polyfluoroalkoxy, is a high-performance material composed of tetrafluoroethylene and perfluoroalkoxy vinyl ether, also known as fusing polytetrafluoroethylene.

PFA is a copolymerization of perfluoropropyl perfluorovinyl ether and polytetrafluoroethylene, which has excellent melt bonding properties and low melt viscosity, while maintaining the excellent properties of polytetrafluoroethylene, and can be processed by conventional thermoplastic molding methods.

With a long-term temperature range of -80 to 260°C, PFA exhibits excellent chemical resistance and is resistant to almost all chemicals. Its friction coefficient is extremely low, excellent electrical performance, electrical insulation is not affected by temperature changes, known as the "king of plastics".

The chemical resistance of PFA is similar to that of polytetrafluoroethylene, but better than that of vinylidene fluoride.

PFA is superior to polytetrafluoroethylene in creep resistance, compressive strength, tensile strength and elongation, and has excellent dielectric properties and radiation resistance, and flame retardant properties are also very significant.

PFA is non-toxic and harmless, is physiologically inert, and can even be used in human implants

Second, PFA material molding and processing technology

The processing technology of PFA resin mainly includes three methods: die molding, extrusion molding and injection molding.

It is suitable for PFA products with melting finger in 0.8~3.0g/10min. These products have high molecular weight and high viscosity and are suitable for molding. The temperature range of the molding is 330~380℃, and the pressure is 5.0~14.0MPa, which needs to be kept at the molding temperature for 20~30 minutes, and then slowly cooled to 200~240℃ under pressure. High melt viscosity and high molding temperature of PFA should be considered in mold design.

Extrusion is suitable for PFA products with melting finger greater than 3.0g/10min, mainly used for the production of pipe, cable insulation layer and film. The screw length-diameter ratio of PFA extrusion is usually 20:1, the extrusion temperature is controlled at 330~425℃, and the speed is 3~50r/min. Due to the high melt viscosity of PFA, a high draw ratio is required during extrusion to obtain a smooth extrusion.

Injection molding is suitable for PFA products with melting finger in 16~30g/10min, suitable for the production of complex shapes of aviation, aerospace industry, electronic and electrical industry parts and medical, chemical test equipment. The screw extruder used in injection molding has strong plasticizing ability, uniform mixing material, less hysteresis and fast stress transfer to the mold.

Third, the application of PFA materials in the field of wire

PFA materials perform particularly well in the field of wire and cable insulation. It can be used at a high temperature of 260 ° C, making it ideal for the manufacture of heating wires and special wires.

(1) Heating wire

PFA heating wires are ideal for heating systems due to their high temperature and stress cracking resistance. Compared to traditional steam heating, PFA heating wires provide better insulation, convenient control and economy. Especially in shorter pipeline heating, PFA heating wires are more widely used. For long distance pipeline heating, PFA heating wires may not be the best choice due to voltage drop issues.

SECT method is a pipeline heating method using the surface effect of alternating current. The PFA wire is heated by alternating current in the SECT tube to heat the inner wall of the pipeline. This structure not only uses the heat resistance and stress cracking resistance of PFA, but also uses its low friction, so that PFA wire can be smoothly laid in the heating steel pipe.

(2) Special wires

In the field of geothermal power generation, the application of PFA cables is also very critical. Geothermal power generation requires converting high-temperature, high-pressure steam deep underground into electricity through turbine generators. In this environment, the cable needs to withstand high temperatures and hydrogen sulfide gas corrosion. PFA cables are ideal for geothermal exploration and power generation due to their high temperature steam and corrosion resistance.