For people familiar to the PTFE industry, it is well known that PTFE can’t be melt-processed. This means that PTFE polymers can’t be directly extruded like other thermoplastics.
Therefore, 3 main processes allow to produce tube-shaped PTFE parts:
The molding process is a process available for tubes and for shapes like sheets or rods. It includes compression of PTFE powder, followed by heating at high temperature and cooling the shape. During heating, PTFE grains merge, in a so-called sintering process.
Ram extrusion combines the molding process with extrusion, allowing a continuous operation of compression, sintering and cooling of the tube. It allows for longer lengths in production, up to 3 m long, while molding often allows a maximum of 1 meter long.
Thin Wall Tubes, also referred as TWT, are the preferred product when it comes to long rolls of flexible tubes. It is for example the process for tubes used as filament guide in 3D printers, or for drinking water handling in home appliances. This process is the most similar to usual extruders, although PTFE is not melted. Just like thermoplastic extrusion, TWT PTFE tubes can reach a few thousand meter’s long, depending on the diameter of the tube. Compared to other processes, it allows for thinner tubes and is the only available process to reach the smallest diameter in the range. Thin wall tubes can also be convoluted, or even partially convoluted, to increase the bending radius.