Introduction of ptfe welding process

Steel lined ptfe equipment is usually made with discharge port, feed port, perspective mirror, etc., but how to successfully apply this kind of pipe port in the complex head intersecting line, of course, our answer is welding, then how to welding?How to control the temperature of ptfe welding?Below we tell one by one.

1, ptfe head pipe mouth production

PTFE pipe welding on sealing head to first of all, we should make PTFE sealing head nozzle, according to the size of the nozzle diameter steel head and according to certain proportion by using powder moulding process manufacturing nozzle, 8 hours of sintered under the 380 plus or minus 5 degrees Celsius, after the completion of the sintering good nozzle with lathe car to the right size, to the congratulations of PTFE tube at this moment you have finished.

2, ptfe head opening

Put the extracted head into the steel head, and use the principle of light transmission to accurately open the head, pay attention to the ptfe head must be consistent with the steel head, or the final equipment is prone to bulge, rupture and other potential hazards.

3, ptfe pipe mouth welding

By the first two steps, we can carry out PTFE welding. Here we know that there are two ways of welding (hot pressure welding and hot air welding). We will explain them one by one.

(1) hot pressure welding

Before hot pressure welding we should know the necessary theoretical knowledge, hot pressure welding is a kind of hot welding, provide sufficient heat and enough pressure.Here, we must ensure that the welding interface temperature must reach 673.15k and the pressure reaches 1-2mpa. Therefore, in order to ensure the welding, we need to make corresponding molds to ensure the successful completion of the thermal pressure welding.When all is done, the FEP film can be welded by pressurizing and heating the interface between the nozzle and the head.

(2) hot air welding

Similarly, ptfe hot air welding is a kind of hot welding, which is much simpler than hot pressure welding and does not require so many molds. After placing the pipe mouth, PFA welding rod and hot air welding gun higher than 713K are used to preheat PFA first and then place it on the welding seam for continuous welding.

Note: whether it's hot pressure welding or hot air welding welding temperature will be higher than the melting point of ptfe, ptfe is possible under the temperature cracking, produces in the process of pyrolysis perfluorinated isobutylene and other poisonous gases, so the welding should be in a ventilation environment, when the condition does not allow such as the four fluorine lining tank welding in production must use the fan air supply air flow assurance and wearing a gas mask to ensure security at the same time.

Introduction to ptfe teflon pipes

Ptfe teflon tube extrusion machine is divided into many kinds, exactly say ptfe tube forming process has push and pressure method, extrusion method, hydraulic method, welding method, winding method, etc., which is mainly push and pressure method.Generally dispersed PTFE resin with particle size of 500 microns and apparent density of 0.45g/ml ~ 0.55g/ml is adopted.The small diameter tube chooses the compression quite big resin, the medium and large diameter tube chooses the compression quite small resin.Extruder usually choose 200 and 260 solvent oil.PTFE thermal shrinkage tube, PTFE spiral tube, PTFE steel wire reinforced hydraulic tube and so on can be produced by the secondary processing of PTFE tube.

1.1 common ptfe teflon pipe

Ptfe ordinary tube is made of ptfe dispersion resin at room temperature with organic solvent as extruder, and then through drying and sintering.According to the size of the pipe diameter can be divided into two types of ordinary pipe and micro pipe.Ordinary tube inner diameter > 4mm, micro tube inner diameter ≤4mm.

Typical formula for PTFE tube production:

Dispersed PTFE resin: 100 (weight)

Extruder: 18 ~ 24

Production process:

PTFE, extruder - mixing - pushing - pressing - drying - sintering - cooling - products.

Production process parameters:

Mixing: temperature ≤19 ℃, time 10min ~ 20min, mixed at 25 ℃ ~ 30 ℃ for more than 24h.

Blank: compression rate is about 50mm/ min, pressure is 0 ~ 3MPa.

Pushing pressure: the cavity temperature is 30 ℃ ~ 50 ℃, and the die temperature is 50 ℃ ~ 60 ℃.

Drying: under 210 ℃,2h ~ 3h

Sintering: batch sintering, temperature rise rate of 60 ℃/ h,375 ℃±5 ℃ insulation for 4h.

Continuous sintering, dry area 100 ℃ ~ 250 ℃, preheating area 250 ℃ ~ 330 ℃, sintering area 380 ℃ ~ 420 ℃, cooling area less than 300 ℃.

Main equipment: mixing machine, preforming machine, vertical pushing press, drying and sintering furnace.

USES: as insulation and fluid conduit.

1.2 polytetrafluoroethylene heat-shrinkable tube

PTFE thermal shrinkable tube has the property of being heat-shrinkable, so it can be tightly coated on the surface of other workpieces, making the workpieces resistant to corrosion, electrical insulation and viscosity.Widely used in electrical, chemical, mechanical, printing and other industries.The maximum shrinkage of PTFE shrink tubes is reported to be more than 75%.

It is processed by disperse PTFE resin. The principle is that PTFE is subjected to stress during processing and produces forced high-elastic deformation, which is reversible and freezes at low temperature. If the forced high-elastic deformation is reheated, it will gradually disappear and return to the original state.

Typical formula for PTFE thermal shrinkable tube production:

Disperse PTFE resin 100 (weight)

Extruder 20 ~ 22

Production process:

PTFE resin, extrusion aid → mixing → storage → pre-molding → pushing and pressing → drying → sintering → cooling → heat treatment → blowing → cooling → product.

Production process parameters:

The front part is the same as ordinary PTFE tube.

Heat treatment: the quenching process of the dried and sintered pipes after further full sintering at high temperature, the temperature is 390 ℃±2 ℃, and the coolant is -5 ℃.

Blowing: at 310 ℃ or so, fill the compressed gas below 0198MPa, the blowing rate is 200% ~ 400%.

Main equipment: blowing machine, other PTFE tube and the same.

1.3 ptfe teflon steel wire reinforced hydraulic pipe

The common PTFE pipe will break under the pressure of about 40kg/ cm2. When it is combined with steel wire, the pressure resistance will be greatly improved. The maximum working pressure abroad reaches 700kg/ cm2.The results show that the compressive strength and pulse strength of the hose are related not only to the steel wire strength but also to the weaving Angle.When the braiding Angle is 54°44 "for single-layer braiding, the steel wire does not extend under internal pressure, the length and diameter of the hose do not change, and the pressure resistance is the best.

When used as hose for hydraulic system in aviation industry, in order to prevent electrostatic breakdown of inner tube caused by hydraulic oil flow, trace conductive carbon black should be added in the manufacture of PTFE inner tube.However, it was found that adding carbon black could not completely prevent electrostatic discharge from passing through the tube wall and increase the gap.

In the 1960s, Attas manufactured composite tubes, in which the inner layer of the tubes was a uniform mixture of conductive carbon black and PTFE, and the outer layer of the tubes was pure PTFE.This form of tube body layer has axial conductivity, so it can not only eliminate static electricity, but also prevent seepage.

The process:

Inner resin (including conductive carbon black), outer resin → blank → pushing → drying → cooling → testing → weaving → fitting joints → testing.

PTFE steel wire composite hose is mainly used in aircraft hydraulic system, air conditioning system, fuel system, lubricating oil system.In civil industry, it is suitable for soft connection of hydraulic pressure, steam pressure and steam transportation in rubber, plastic, pharmacy, clothing, shipbuilding, automobile, machine tool, motor, diesel engine and paper making industries.

1.4 ptfe teflon spiral tube

PTFE spiral tube, also known as PTFE flexible hose, has not only all the excellent properties of PTFE, but also flexible properties.At present, there are two kinds of PTFE spiral tube and chemical fiber, stainless steel wire and plastic coated glass fiber woven reinforcement.

It is made of PTFE through secondary processing. The process is that PTFE thin-walled tube continuously rotates forward through a combination mold with a temperature of 270 ℃ ~ 280 ℃ at a certain speed.

It is mainly used for the inlet and outlet pipes of the shock parts such as the soft connection dislocation connection, serpentine pipes, pump engines and so on.Used for shielding cable and protecting cable sleeve of aircraft engine.