PTFE pipe introduction

PTFE pipe introduction

       The forming process of the PTFE pipe has a pressing method, an extrusion method, a hydraulic method, a welding method, a winding method, and the like, and the pressing method is mainly used. Generally, a dispersed PTFE resin having a particle diameter of 500 μm and an apparent density of 0.45 g/ml to 0.55 g/ml is used. The small diameter tube is made of a resin with a relatively large compression, and the large and medium diameter tube is made of a resin with a relatively small compression. The propellant is usually selected from solvent oils No. 200 and No. 260. The PTFE pipe is subjected to secondary processing to obtain a PTFE heat shrinkable pipe, a PTFE spiral pipe, a PTFE steel wire reinforced hydraulic pipe, and the like.

      1.1, Teflon ordinary tube

The Teflon common tube is made by pressing a polytetrafluoroethylene dispersion resin at a normal temperature with an organic solvent as a squeezing agent, and then drying and sintering. According to the size of the pipe diameter, it can be divided into two types: ordinary pipe and micro pipe. Ordinary tube inner diameter > 4mm, micro tube inner diameter ≤ 4mm.

      Typical formulations for the production of PTFE tubes:

      Dispersed PTFE resin: 100 parts by weight

      Squeezing agent: 18~24

      Production process:

      PTFE, squeezing agent → mixing → pressing → drying → sintering → cooling → product.

      Production process parameters:

      Mixing: Temperature ≤19 °C, time 10min~20min, mixing at 25 °C ~ 30 °C for more than 24h.

      Billet: The compression rate is about 50mm/min and the pressure is 0~3MPa.

      Pushing: the temperature of the cavity is 30 °C ~ 50 °C, the die temperature is 50 °C ~ 60 °C, the pushing rate becomes smaller with the increase of the pipe diameter, and accelerates as the wall thickness becomes smaller.

      Drying: below 210 °C, 2h~3h

      Sintering: batch sintering, heating rate 60 °C / h, 375 °C ± 5 °C for 4h.

Continuous sintering, drying zone 100 °C ~ 250 °C, preheating zone 250 °C ~ 330 °C, sintering zone 380 °C ~ 420 °C, cooling zone less than 300 °C.

      Main equipment: mixer, pre-former, vertical pusher, drying and sintering furnace.

Uses: as insulation and conveying fluid conduits.

      1.2, Teflon heat shrinkable tube

      The PTFE heat shrinkable tube has the property of being heat-shrinked, so it can be tightly coated on the surface of other workpieces, making the workpiece corrosion-resistant, electrically insulating and anti-adhesive. Widely used in electrical, chemical, mechanical, printing and other industries. The maximum shrinkage of PTFE heat shrink tubing is reported to be greater than 75%.

      Made of dispersed PTFE resin, the principle is that PTFE is subjected to stress during processing to produce forced high elastic deformation. This deformation is reversible, and the low temperature makes it freeze. If reheated and frozen, the forced high elastic deformation will gradually disappear and Revert to the original state.

      Typical formulations for the production of PTFE heat shrink tubing:

      Dispersed PTFE resin 100 (parts by weight)

Squeezing agent 20～22

   Production process:

PTFE resin, extrusion aid → mixing → storage → preforming → pressing → drying → sintering → cooling → heat treatment → inflation → cooling → product.

Production process parameters:

The front part is the same as a normal PTFE tube.

Heat treatment: The process of quenching the dried and sintered pipe again after further sintering at a high temperature again, the temperature is 390 °C ± 2 °C, and the coolant is - 5 °C.

Inflation: At about 310 °C, it is filled with a compressed gas of 0198 MPa or less, and the inflation rate is 200% to 400%.

Main equipment: Inflator, the other is the same as ordinary PTFE tube.

1.3, PTFE steel wire reinforced hydraulic pipe

       The ordinary PTFE tube will be ruptured under the pressure of about 40kg/cm2. When it is combined with the steel wire, the pressure resistance is greatly improved, and the maximum working pressure in foreign countries reaches 700kg/cm2. Studies have shown that the compressive strength and pulse strength of the hose are not only related to the strength of the steel wire, but also to the size of the braiding angle. When the weaving angle of the single layer weaving is 54° 44′′, the steel wire does not elongate under the internal pressure, and the length and diameter of the hose do not change, and the pressure resistance is the best.

When used as a hose for aerospace industrial hydraulic systems, in order to prevent static breakdown of the inner tube due to the flow of hydraulic oil, a small amount of conductive carbon black must be added during the manufacture of the PTFE inner tube. However, studies have found that the addition of carbon black does not completely prevent static electricity from discharging through the tube wall and increases voids.

       In the 1960s, Attas manufactured a composite tube, in which the inner layer of the tube was a uniform mixture of conductive carbon black and PTFE, and the outer layer of the tube was pure PTFE. This form of inner tube layer has axial electrical conductivity, so it can remove static electricity and prevent seepage.

       Its process:

       Inner layer resin (including conductive carbon black), outer layer resin → compact → push → dry → cooling → inspection → weaving → fitting → inspection.

       PTFE steel wire composite hoses are mainly used in hydraulic systems, air-conditioning systems, fuel systems, and oil systems on aircraft. In the civil industry, it is suitable for rubber, plastic, pharmaceutical, clothing, shipbuilding, automotive, machine tools, motors, diesel, paper and other industries for hydraulic, steam pressure, steam delivery and other soft connectors.

1.4, PTFE spiral tube

PTFE spiral tube, also known as PTFE flexible hose, has flexible properties in addition to all the excellent properties of PTFE. At present, there are two types of pure PTFE spiral tubes and chemical fibers, stainless steel wires and plastic coated glass fibers.

       It is made by PTFE whole secondary processing, which is made by continuously rotating the PTFE thin-walled tube continuously through a combined mold with a temperature of 270 °C ~ 280 °C at a certain speed.

       It is mainly used for the connection of the flexible connection of the corrosion-resistant and high-temperature resistant equipment, the misalignment connection, the serpentine pipeline, the pump engine and other shocking components. Shielded cables and protective cable bushings for aircraft engines.