The insulating material used as insulated wire is mainly PFA. According to the processing characteristics of PFA, the following three processing techniques are generally used.

1. Hot Extrusion Process When the barrel temperature inside the extruder reaches about 350°C -390°C, F46PFA is added into the hopper, and the conductive wire core is uniformly and continuously covered by the forming die by using the thrust of the screw rotation, and is shaped after cooling. This method uses Φ30, Φ60, Φ90 and other high-temperature plastic extruders to produce PFA insulation products such as F46 and F40.

2, pushing the process of powderyPFA GranulesPre-press into a barrel type, put into the barrel, use the piston thrust, through the molding die uniformly and continuously covered on the conductive core, and then 380. C high temperature sintering, cooling after shaping. This method uses an F4 push press to produce F4(PTFE) type products.

3. In the wrapping process, the PFA film tape cut into a certain width is wrapped around the wire core, and then sintered and shaped. This method uses a winding machine and a sintering furnace to usually produce AFR type, FSFB type and other wires.

A. Development of PFA Extrusion Process

PTFE can not melt extrusion, must be wrapped by film or paste extrusion to produce wire and cable, the use of special equipment, equipment complex, long process, and production is intermittent, production speed is also limited. Therefore, the development of melt-extrudable PFA has been a major issue in the polymer community. FEP was the first successfully developed melt-extrudable PFA. It maintains almost all the excellent properties of PTFE, and is still the most widely used and the largest amount of PFA except PTFE. The continuous use temperature of FEP is 200 ℃, and the successful development of PFA has led to the real melt extrusion PFA that can be used at 250 ℃, but it is expensive. ETFE and PFA particles, while basically maintaining the various properties of PTFE, have emerged in PFA with their three advantages of small specific gravity, high strength and radiation resistance, and have also been widely used in wire and cable.

B.PFA extrusion equipment

In addition to PFA particles allow the use of general extruder extrusion wire, other various PFA use high temperature extruder production wire and cable. Requirements for high-temperature extruders for molten fluororesin: sufficient heating power to ensure that the resin can be melted and extruded at high temperatures (for example, about 450 ℃); parts in contact with the melt: screw, screw, head and its components, Mold, etc., must use high-temperature corrosion-resistant alloys, such as nickel-based alloys (including domestic new No. 3 steel), this is mainly due to the strong corrosiveness of fluorine-containing gases such as HF that may be generated during the extrusion process.

C.PFA extrusion material

With different PFA have different use temperature, conductor also need different applicable temperature. Considering the corrosion of the conductor by the gas that may be generated during extrusion, almost all PFA wires and cables use silver plating, tin plating, nickel plating and other plated conductors. Wire and cable research and producers should correctly select conductors and insulating materials according to the needs of wire and cable users, not only to meet customer requirements, but also to make the insulating materials use just right. Therefore, we should be familiar with and master the characteristics of various PFA.

D.PFA extrusion process

The melt viscosity of the melt containing PFA is extremely large, so it is not suitable to use "pressure type" extrusion (otherwise it will put too strict requirements on the equipment); but the melt has sufficient strength to allow stretching, so almost all of them are used "sleeve type" Extrusion to produce wire and cable, through the control of reasonable tensile coefficient to ensure the adhesion between insulation and conductor. In the "casing type" extrusion, the design of the die or the "matching die" in the production should ensure that the value of the two parameters of DDR and DBR is within the reasonable range allowed by the extrusion material.

This article comes from:www.tflpfa.com

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