I’ve spent a lot of time in plants where a tubing mistake leads to swelling, odor, embrittlement—or worse, an unexpected release that trips safety systems and halts production. Chemical-resistant pneumatics aren’t just about surviving the media; they’re about protecting valves, seals, sensors, and operators. The pain points I hear most often: “Will this tubing hold up to my solvent blend?”, “Why do I smell ketone near the manifold?”, and “Why did the line lose pressure after a weekend shutdown?”
For chemical‑resistant pneumatic applications, I prioritize fluoropolymers (PTFE, PFA, FEP) or PVDF for most aggressive media, and PEEK or 316L stainless steel when high pressure, high temperature, or permeation control is critical. Nylon and polyurethane are acceptable for milder environments, but they fall short with strong acids, bases, and many hydrocarbons. Always verify the exact chemical, concentration, temperature, pressure, and exposure duration against the manufacturer’s compatibility chart and request certifications to validate safety and performance.
In the sections below, I’ll compare PTFE vs PFA for solvents and heat, assess whether nylon or polyurethane can meet bend radius and exposure requirements, walk through how I use compatibility charts with real plant data, and list the certifications I ask vendors to provide. I’ll also cover fittings and seals, permeation realities, and how to avoid common failure modes in chemically active environments.
Is PTFE or PFA a better fit for my solvents and temperatures?
Fluoropolymers: where I start for aggressive media
- PTFE (polytetrafluoroethylene) gives the broadest chemical resistance I’ve seen in pneumatics—strong acids (HCl, HNO3), bases (NaOH), halogenated and oxygenated solvents (MEK, acetone), and many hydrocarbons. It’s stable up to ~260°C (500°F) and has excellent non-stick surfaces. Downsides: lower flexibility, tendency to cold flow, and opaque appearance. It can kink in tight runs without reinforcement or spring guards.
- PFA (perfluoroalkoxy) matches PTFE’s resistance profile but is more flexible and transparent. That clarity is useful for visual inspection and cleanroom applications. PFA handles similar temperatures (~260°C) and is easier to flare or heat-form for clean connections.
- FEP (fluorinated ethylene propylene) offers comparable chemical resistance with the best clarity of the three, but a slightly lower continuous temperature capability (~200–205°C). It’s a good pick when you need visual confirmation and moderate temperatures.
Permeation and process impact
- All fluoropolymers resist chemical attack yet can permit vapor permeation. If you run ketones, aromatics, or CO2, expect vapor migration that can cause odor, soften nearby elastomers, or drift sensor readings. In those cases, I switch to PEEK or 316L stainless steel to suppress permeation, or I relocate sensitive components and improve ventilation.
Mechanical trade-offs and fittings
- PTFE’s bend radius is larger; use supports, clamps, or convoluted PTFE when routing in tight panels. PFA offers a tighter bend radius and better resilience.
- For fittings, I avoid brass in aggressive solvent service and prefer 316L compression fittings or all‑fluoropolymer connections. Use compatible ferrules and seals (PTFE, PFA, or FFKM perfluoroelastomer) to prevent failures at the connection points.
Can nylon or polyurethane meet my chemical exposure and bend radius needs?
Where nylon and PU fit—and where they don’t
- Nylon 12 is strong, abrasion‑resistant, and holds high working pressures. It resists many oils and some hydrocarbons better than PU, but it does not tolerate strong acids/bases or aggressive polar solvents long-term. I use nylon for general air service, oily environments, and control lines—not for concentrated acids or ketones.
- Polyurethane (ether‑based for hydrolysis resistance) delivers outstanding flexibility and tight bend radius for dynamic tooling, gantries, and cobots. Chemical resistance is modest; it fares poorly with strong acids/bases and many solvents. PU is excellent for motion; not for aggressive chemistry.
Practical routing and lifecycle
- If your priority is tight routing and repeated flexing, PU is ergonomic and cost‑effective. In chemically active areas, I’ll shield PU runs, elevate them away from spills, or specify drip trays and quick isolation.
- Nylon can bridge the gap when you need more pressure capacity and abrasion resistance with moderate chemistry—but I don’t treat it as “chemical resistant” in the same league as fluoropolymers.
Quick comparison table: materials at a glance
| Tubing Material | Chemical Resistance (overall) | Typical Temp Range | Flexibility/Bend Radius | Permeation Risk | Typical Use Case |
|---|---|---|---|---|---|
| PTFE | Excellent (acids, bases, solvents) | up to ~260°C | Low (stiffer) | Medium | Aggressive media, high temp |
| PFA | Excellent (similar to PTFE) | up to ~260°C | Medium (better than PTFE) | Medium | Clean/transparent, visual inspection |
| FEP | Excellent (slightly lower temp) | up to ~200–205°C | Medium–High | Medium | Highest clarity, moderate temp |
| PVDF | Very good; strong vs acids/oxidizers | ~-40 to 150°C | Medium | Lower than fluoropolymers | Purity, abrasion resistance |
| PEEK | Very good + high pressure | up to ~250–260°C | Low–Medium | Low | High-pressure, permeation control |
| 316L SS | Very good (many corrosives) | >260°C (by system) | N/A (rigid) | Very low | High-pressure, low-permeation lines |
| Nylon 12 | Moderate (oils, some HC) | ~-40 to 93°C | Medium | Medium | General air, oily environments |
| PU (ether) | Limited (mild chemicals) | ~-40 to 80°C | High (tight radius) | Medium | Dynamic motion, general pneumatics |
How do I use a chemical compatibility chart with my exact media and pressure?
My step-by-step method
- Identify the exact chemical name and CAS number. “Solvent” is too vague—MEK behaves differently than IPA or toluene.
- Define concentration, temperature (steady and peak), and exposure type: continuous flow, intermittent splash, vapor exposure, or CIP/cleaning cycles.
- Note pressure and cycling: static pressure vs pulsation; higher pressure hastens stress cracking in some polymers.
- Check multiple manufacturer charts. Ratings vary; I look for A/B/C/D style or “Excellent/Good/Fair/Poor,” and I cross-reference at the stated temperature. I prefer charts that include notes on permeation or swelling.
- Validate elastomers and fittings as a system. O‑rings (FKM vs FFKM vs EPDM), ferrule materials, and valve body alloys can be the weak link.
- Run a soak/permeation test with a sample length if the media is aggressive or mixed (e.g., ketone/aromatic blends). Measure mass change, odor, and dimensional stability after 24–72 hours.
Interpreting ambiguous cases
- If the chart says “conditional” or “fair,” I consider duty cycle and safety margin. For continuous exposure, I move up to PFA/PTFE or PVDF. For intermittent rinse at room temp, nylon might be acceptable.
- For vapor‑rich environments (acetone, methylene chloride, CO2), I estimate permeation impact on nearby sensors and elastomers; if in doubt, I choose PEEK or 316L.
Minimal data you should record
- Chemical name + CAS
- Concentration (%), temp (steady/peak)
- Pressure (steady/peak), cycle profile
- Exposure duration per shift/week
- Required bend radius and routing constraints
- Compliance/certifications required
What certifications should I ask for to verify resistance and safety?
Certifications and documentation I request
- Material traceability and resin grade declaration (e.g., PTFE/PFA grades, PVDF homopolymer vs copolymer, PEEK grade).
- ISO/ASTM conformance relevant to tubing (e.g., ASTM D3294 for PTFE; ASTM D543 for chemical resistance testing results; pressure test reports).
- Oxygen cleaning or contamination control certificates if the air stream supports oxidizer handling (ask for process notes: solvent used, particle counts).
- USP Class VI or FDA/NSF 51/61 when purity, potable water, or food contact is relevant (common with PVDF, PFA, PTFE in sanitary areas).
- UL 94 flammability rating for tubing in panels near electrical gear.
- RoHS and REACH declarations for plant compliance; halogen and plasticizer disclosures for EHS.
- For stainless steel: material test reports (MTRs), 316L composition, pickling/passivation records, and pressure rating per design code.
- Manufacturer’s chemical compatibility chart reference, test methodology, and any permeation or vapor transmission data for the specific media.
Don’t forget the connection hardware
- Request wetted‑materials BOM for fittings/valves: 316L bodies, PTFE/PFA seats, FFKM O‑rings for aggressive chemistries.
- Ask for Cv values and leak‑rate specs (sccm at test pressure); low leak rates matter when permeants are hazardous or odorous.
- Verify FRL elements (filters/regulators/lubricators) are compatible; in chemical service I avoid inline lubricators and choose dry air with fine filtration (coalescing 0.01–0.1 µm) to prevent reactions.
Selection matrix: pairing tubing to real-world needs
| Requirement | Recommended Tubing | Notes |
|---|---|---|
| Strong acids/bases, high temp | PTFE or PFA | Use FFKM seals; expect some permeation |
| Visual inspection in clean areas | PFA or FEP | PFA for higher temp; FEP for best clarity |
| Low permeation, high pressure | PEEK or 316L SS | Ideal near sensitive sensors or VOC limits |
| Purity + abrasion resistance | PVDF | Good balance of strength and cleanliness |
| Tight bend radius, dynamic motion | PU (ether-based) | Shield from chemicals; great flexibility |
| General plant air with oils | Nylon 12 | Avoid strong acids/bases/ketones |
My closing advice
- Start with fluoropolymers for aggressive chemistries. If vapor permeation compromises the area, move to PEEK or 316L for critical runs.
- Treat the system holistically: tubing, fittings, seals, FRLs, and valve bodies must all be compatible.
- Document your exact media conditions and validate with the manufacturer—charts differ, and your duty cycle matters more than a generic “resistant” label.
Conclusion
In chemical‑resistant pneumatic applications, I don’t gamble on general‑purpose polymers. PTFE, PFA, and FEP deliver broad resistance; PVDF offers purity and strength; PEEK and 316L solve high‑pressure and permeation problems. Nylon and polyurethane are excellent in their lanes—general air and flexible tooling—but not for harsh chemistries. Use precise media data, validate against multiple compatibility charts, and demand certifications that prove material, cleanliness, and performance. Finally, engineer the connections: ferrules, seals, and valve internals decide whether your tubing choice succeeds long term.
