PTFE Tubing extrusion
is among the most difficult processes within the purview of the polymer space.
All polymers have their set of peculiarities and these play a part in things
like processing and machining. But PTFE tube comes with different process
parameters, and finding the right combination that works consistently is
something that not every tube manufacturer will know. Let’s find out some of
the parameters here followed by PTFE hose manufacturers.
Handling: Handling resin is among the most important but
easily overlooked part of PTFE processing. While many resin
manufacturers give out layout guidelines for providing the shear on the resin
before the processing starts these are more important for the tubing.
Blending: The parameters about blending include the type of
extrusion aid used. The blending needs to be done in the correct manner, the
final extrude will either too soft or too dry. Furthermore, the blend has to be uniform, the preform
billet will have uneven densities, causing issues during the extrusion.
Preforming: Preforming
is done to create a shape that can fit into an extruder.
- Preforming has two functions: first, it provides a solid shape and second, it also removes any air pockets form within the material. The process needs to be done in a way to keep too little pressure and not go for enough venting of the air inside the material.
Extrusion: While extrusion is understandably the most
important step, by the time the preform billet is loaded into the extruder, the
preceding processes have already defined a lot of the tube’s final
characteristics. Extrusion gives it the final shape and this process helps
maintain both adequate pressures on the billet while maintaining the
concentricity of the final tube.
Sintering: Heat the tube in a way that the temperature needs
to account for both a drying section and the sintering section. The drying
section should be warm enough to evaporate all the traces of vapor from the
tube. At the same time, if it is too warm, the vapors may start getting
ignited. If the tube gets heated too quickly, there is a chance of
over-sintering. Too much heat can cause dimensional deviations. In PTFE. Therefore
the temperature must turn out the PTFE in a ‘gel state’ just before it leaves the
sintering chamber and then cool down at room temperature.
The PTFE tube also undergoes a process called
pigmentation, the addition of anti-static fillers also extrusion of specific
profiles. All the above processes need to be modified to allow a proper
end-result.
