FEP Special Parts

What FEP does that PTFE cannot

FEP is a copolymer of tetrafluoroethylene and hexafluoropropylene. Chemically it behaves like PTFE — inert to most acids, bases and solvents, non-stick, an excellent electrical insulator. What separates the two is processing and appearance. PTFE cannot be melt-processed, so a PTFE part is compression moulded or machined from a billet, and it is opaque white. FEP flows at about 260 °C, so it can be extruded into tube and profile, injection moulded, heat formed and welded. It is also transparent, which turns a fitting into a window.

That combination is why FEP special parts appear wherever the shape is awkward and the fluid has to be seen: transition pieces between glass and plastic tubing, sight components on dosing lines, protective liners inside small housings, and plugs that must not scratch the bore they sit in.

The honest limit: FEP is softer and less heat-resistant than PTFE. Above about +200 °C, or where the part carries structural load, PFA or PTFE is the right material and FEP is the wrong one.

FEP against PTFE and PFA

The practical rule: if the part must be seen through, FEP is the cheap answer and PFA is the hot answer. If the part must be machined from stock and cost matters, PTFE wins. If it is a one-off with a complicated profile and no temperature problem, FEP is usually the fastest route.

Parts we make in FEP

• Transition fittings between tube, hose and a threaded port, including stepped and reducing forms.
• Plugs, caps and protective inserts for bores, ports and transport protection.
• Liners and sleeves that isolate a small housing, sensor or probe from the process.
• Sight and flow parts where the transparency is the function, not a bonus.
• Insulating parts for electrical or thermal separation in instrument assemblies.
• Formed and welded assemblies where a single moulding cannot reach the shape.

Most of these begin as a drawing of an existing part that has failed, or as a sketch of one that does not exist yet. Both are workable starting points. Where the part is a copy, send the original: measuring a deformed part tells us what it has to become, not only what it was. Custom work of this kind sits alongside our PTFE parts range, and the same drawing discipline applies to both.

Where these parts are specified

Chemical plant and lab apparatus

Transition pieces and sight parts on small-bore lines handling acids, solvents and plating baths.

Medical and diagnostic equipment

Transparent connectors, liners and plugs where the fluid path must be visible and cleanable.

Cooling and air-conditioning equipment

Insulating and transition parts in condensate and refrigerant-adjacent assemblies.

Water treatment and dosing

Sight components and liners on hypochlorite, ferric chloride and caustic feed lines.

Semiconductor and high-purity lines

Small transparent parts where metal contamination is the failure mode.

Analytical instruments

Flow cells, probe sleeves and isolating parts that must not absorb the sample.

Where the assembly also needs a flexible run of tubing, FEP or PTFE-lined parts are usually specified in the same grade so the wetted path has no change of material and no step.

What to send, and what you get back

A drawing is ideal, a dimensioned sketch is workable, and a photograph with a ruler is enough for a first opinion. The points that decide the price are the wall thickness, the tolerance on the sealing face, the number of secondary operations and whether a tool is needed.

• Drawing, sketch or sample, with the critical dimensions marked.
• Media, concentration, temperature and pressure — together, not one at a time.
• Quantity for the first order and the expected annual volume.
• Any documentation your audit requires, named before the order.

Prototypes are usually machined or hand-formed from stock, so nothing is spent on tooling before the design is fixed. Once the shape is stable, extrusion or moulding brings the unit cost down. Production and finishing run in our own Ningbo workshop, and technical sales answers within 2 business hours.

Questions buyers ask before the first order

What are FEP special parts?

They are custom components made from FEP, a transparent melt-processable fluoropolymer, by extrusion, injection moulding, heat forming or machining. Typical parts are transition fittings between tube and thread, plugs and caps, liners, sleeves and sight parts for chemical, medical and cooling equipment.

Is FEP the same as PTFE?

No. Both are fluoropolymers with similar chemical resistance, but FEP is melt-processable and transparent, with a continuous service limit near +200 °C. PTFE is opaque, not melt-processable, and goes to about +260 °C, which is why PTFE is normally machined or compression moulded while FEP can be extruded and heat formed.

Can FEP parts be machined?

Yes, as a finishing operation: facing, boring, grooving and drilling are all routine. Complex or thin-walled shapes are better formed than cut, because FEP is soft and flexible at room temperature. Threads in FEP are weak, so a metal insert or a clamped joint is usually the better design.

What temperature can FEP parts take?

Continuous service runs from −200 °C to about +200 °C, and the practical ceiling falls as pressure and mechanical load rise. Above that, PFA or PTFE is the correct material. Tell us the temperature and the pressure together, because one rating without the other is misleading.

Are FEP parts suitable for medical and food contact?

FEP is widely used in medical and food-contact applications, but the answer depends on the grade and the paperwork, not on the polymer name alone. Tell us the standard your audit applies and we will confirm which grade, and which documentation, we can supply.

Can you make one prototype and small batches?

Yes. A prototype is usually machined or hand-formed from stock, so no tooling is needed until the design is fixed. Once the part is stable, extrusion or moulding brings the unit cost down. Minimum order quantity depends on the process and the drawing.