You order ECTFE film for a chemical barrier layer, or ECTFE sheet for a process tank wall. The part looks right on delivery, but a week later the dimensions have drifted. Or a weld seam that looked clean cracks during the first heat-up cycle. In most cases, the material is not the problem. The cause lies in the choice of form or in the way it was processed. This article explains which form suits which application and which properties determine processing. You then get a five-step plan to turn semi-finished products into dimensionally stable, reliable parts.
Engineers used to stainless steel or PP often underestimate ECTFE. Three differences account for most rejected parts.
Thermal expansion. ECTFE expands considerably more than metal when temperatures change. A part that is within tolerance at 20 °C in the workshop can bind or leak at operating temperature.
Residual stress. Stress builds up through heat during machining, removing too much material in one pass, or clamping too tightly. It is released later as warping or cracking.
Welding parameters. Too low a temperature causes incomplete fusion. Too high a temperature or too long a heating time degrades the material. Neither fault is always visible from the outside.
The result is rework or scrap. In the worst case, a part fails in service, causing leakage and downtime.
ECTFE, also known by the brand name Halar®, is a melt-processable fluoropolymer. Unlike PTFE, it can be extruded, welded (hot gas and butt welding) and thermoformed. This makes welded assemblies and formed parts possible that cannot be made from PTFE, or only indirectly. A full material comparison is covered in our article ECTFE vs ETFE.
The key values for processing, from the Polyfluor datasheet:
|
Property |
Value |
What it means for processing |
|
Melting point |
240 °C |
Sets the temperature window for welding and thermoforming |
|
Service temperature |
−75 °C to +150 °C (short-term 180 °C) |
Design tolerances at operating temperature, not room temperature |
|
Heat deflection temperature (HDT) |
104 °C (method A) / 71 °C (method B) |
Stiffness under load decreases as temperature rises |
|
Hardness |
70–80 Shore D |
Machines well, but is tough: sharp tools required |
|
Tensile strength / elongation at break |
32 MPa / 200 % |
Tough material that absorbs deformation without brittle fracture |
The form determines which processes are possible. Sheet can be welded, bent and thermoformed. Rod is intended for turning and milling. Film can be cut, laminated or formed, but not machined.
ECTFE sheet is the choice for flat or welded constructions: process tanks, tank walls, fume cabinets, partitions and structural parts. Sheet linings are also possible. Powder coating is covered in our article ECTFE coating.
ECTFE rod is the starting material for turned and milled parts such as seals, valve seats and bodies, fittings, bushings and flanges. Choose a diameter with sufficient machining allowance.
ECTFE film is used wherever a thin layer is enough: as a chemical barrier, protective layer, or release and cover layer. Halar ECTFE film combines chemical resistance with weather resistance. A dielectric strength of 40 kV/mm and a dielectric constant of 2.5 also make it suitable for electrical insulation in electronics.
Unsure which form to choose? Start from the process the part needs. Welding points to sheet, machining to rod, and a thin barrier layer to film.
List what the part has to withstand: medium, temperature (including peaks), pressure and mechanical load. Compare this with the ECTFE datasheet (pdf). Allow for reduced stiffness if the operating temperature approaches 150 °C or the part is under continuous load.
Select the form based on the process required. Order with a machining allowance so you can machine to final dimensions with minimal stress. Check with your supplier which thicknesses and diameters are available in ECTFE.
Specify tolerances at operating temperature and state the measuring temperature on the drawing. Design fits, bolted joints and long flat sections with room for expansion. Overly tight tolerances add cost without functional benefit.
For ECTFE machining, use sharp tools, moderate depth of cut and good cooling so heat does not build up. For ECTFE welding, use hot gas or butt welding with qualified parameters and welders. Thermoforming requires even heating and controlled cooling.
If you have in-house machining and welding capacity with fluoropolymer experience, semi-finished products are the logical choice. If that experience is lacking, or for critical parts, custom finished products often save time and scrap.
A manufacturer in machinery and equipment construction designs a process bath for an aggressive, oxidising medium. Stainless steel is ruled out by corrosion. PP is ruled out by the combination of temperature and chemical load.
The tank is built from ECTFE sheet with hot-gas-welded seams. The connection flanges are turned from ECTFE rod. The long walls get stiffeners and room for expansion, and every seam is inspected after welding.
One question still needs checking: is ECTFE resistant to exactly this medium at this temperature? Use the resistance chart for that. Our article Chemical resistance of ECTFE explains how.
ECTFE is melt-processable, which means that unlike PTFE it can be welded and thermoformed. Choose sheet for welded and formed constructions, rod for machined parts and ECTFE film for thin barrier and insulation layers. Most problems are not caused by the material itself but by thermal expansion, residual stress and incorrect welding parameters. Account for these three from the start and you get dimensionally stable parts with a long service life.
Looking for ECTFE film, sheet or rod, or a ready-made part? Browse our fluoropolymer semi-finished products or contact us. Our specialists will help you with form, size and processing, and are happy to provide a custom quote.
Yes. ECTFE is melt-processable and, unlike PTFE, can be joined by hot gas or butt welding. Weld quality depends on temperature, speed and pressure, so have your parameters and welders qualified.
With a hardness of 70–80 Shore D, ECTFE turns and mills well. Use sharp tools and avoid heat build-up to prevent residual stress. Allow for thermal expansion when setting tolerances.
Typical uses are chemical barrier layers, protective and cover layers, release films and electrical insulation. Halar® is a brand name for ECTFE; the material properties are those of ECTFE.
ECTFE film can be transparent, depending on thickness and grade. If transparency matters for your application, mention it in your enquiry.
As a semi-finished product, ECTFE is commonly available as sheet, rod and film. It is also used as tubing and as a coating. Our specialists can tell you which sizes Polyfluor supplies as standard.