One of the most difficult procedures within the polymer space remains to be PTFE tubing extrusion. All sorts of polymers have specific characteristics that play an important role in their processing. But PTFE comes with such a diverse array of process parameters; identifying the right combination that works coherently is not something every manufacturer is able to achieve.
Even after years of research, with PTFE tubing new process parameters may show up any time. Let’s take a look at some of the most common parameters and how they affect the final product here:
It may perhaps be one of the most easily overlooked aspects of the process. Even though many manufacturers lay out specific guidelines for restricting the shear before processing the resin, these limitations become even more important when tubing is concerned.
The fibrils that are formed during extrusion are of utmost importance when it comes to the strength of the final tubing product.
Excessive shearing often leads to poorly formed fibrils which mean a dramatic drop in quality of the final tubing product.
When blending, the surface tension of the extrusion aid should be less than that of PTFE while not having flash point or volatility enough to raise concerns.
The blending process also includes considering the RPM implemented in the process and post blending storage. Unless the blending is done perfectly, the final product will be either too dry or too soft. The density of the product may also be largely impacted by irregularities in the blending process.
Pre-forming gives the resin its shape and it helps avoid formation of air pockets. The process should be performed keeping in mind lack of adequate pressure could make it impossible to vent out all the air from the product. Even the tiniest of air pockets could render the tube useless by bursting during extrusion. On the other hand, excessive pressure could squeeze out the extrusion aid, making the extrude dry.
Even though the previous steps have already given the tube much of its characteristics, extrusion gives the product its final shape. The process needs to maintain the right pressure on the billet while ensuring the concentricity of the final PTFE tubing.
If the pressure is on the either extremes, it will result in failure to form the product or it may exert too much shear. The concentricity is dependent on the density of the billet and the tooling present within the extruder.
When it comes to heating, the temperature of heat applied should account for sintering as well as drying. Drying should be able to evaporate all vapors from the tube without igniting them. During sintering the temperature should be controlled to minimize chances of over sintering. Even though PTFE doesn’t melt, during sintering it may elongate under its own weight. PTFE should be in gel-like state before it leaves the chamber so it can cool down normally.
Apart from all these processes, PTFE also goes through pigmentation, extrusion of specific profiles and the addition of anti-static fillers. Each part of the process plays a key role in giving PTFE tubing its final form and characteristics.
At Tef-Cap, we make sure that all our PTFE tubing products undergo rigorous quality checks before they make it to clients. Get in touch with us to learn more about our PTFE products today.