PTFE V/S Other Polymers
Most polymers used in creating plastic extruded tubing today have low melting points, making it easy to run the machines at moderate temperatures and create the tubing by extruding through the dies and molds directly from the resin material in the hopper, without any other preparation other than keeping the right mix of resins in the hopper at the correct amounts. Extrusion molding is one of the most economical manufacturing methods for that very reason, less man hours in preparation means less cost to make the final product-Best Plastic Extrusion Machine Supplier.
PTFE or Teflon on the other hand, has a very high melting point as a polymer, and is nigh impossible to use for custom tubing through an extrusion process, unless certain preparations are made in advance before production begins. It is also not as easy to use as is one of the off the shelf polymers that come in resin bead form, either. The original extrusions done in the past required a wire core to be inserted into the mold and the PTFE extruded tubing was created around it so it would not collapse on itself, because it was that delicate. Today's extrusion requires a refined set of steps to get the complete product, and that is what we will cover next-Best Plastic Extrusion Machine Supplier.
Defining today's PTFE paste extrusion process
The PTFE polymer resin comes in a powder form that only has an average grain size of around .2mm. The powder itself is very wax-like, and as such can be easily bruised or sheared through handling, especially with mechanical means. Because of this, the material can only be handled in an environment of around 20C, and must be mixed first with either mineral spirits or some other kind of extrusion aid to bind the material together before processing. That processing will take the following steps:-Best Plastic Extrusion Machine Supplier
Compression: In order to prepare the material for extrusion, the PTFE mix must be first compressed into a billet form using a hydraulic press. This will take around two hours to complete, including dwell time, in order to ensure that no air bubbles remain in the compressed polymer.
Extrusion: The compressed polymer is now loaded into the extrusion mold, with the die and mandrel clamped on. The design of the die will define not only the strength of the resulting tube, but will also determine its final dimensions, including inner wall strength. During extrusion the material is pressed against the die and mandrel, forcing the material into the required shape. Any Teflon tubing produced during this phase is considered to be of "green" material, and it can be easily damaged while in this state.
Curing: The green Teflon tubing is taken from the extruder and passed through an oven at low temperature during this phase. The purpose of this is evaporate the mineral spirits or extrusion binders used to keep the resin together during preparation. Leaving those chemicals within the polymer now could weaken its material strength, and leave it open to combustion should it ever reach the flash point of the mineral spirits while in use. This whole process can take up to 24 hours to complete, depending on the thickness of the finished tubing.
Cutting: Once the PTFE extruded tubing has been cured and all binders have been evaporated, the tubing is first cleaned via oven sterilization, in accordance with the ISO Grade VI clean room guidelines, the minimum requirement for Teflon tubing. The product is then cut into custom lengths for packaging. If the intended product is for use in the medical field, all lengths will have the ends capped as soon as it leaves the oven, preserving the sterilized surface inside the tube prior to packaging and shipping.