Choosing between PTFE and other engineering plastics affects both product performance and manufacturing cost. With years of experience machining precision components across aerospace, medical, and industrial sectors, the right material selection can make or break your project timeline and budget.
PTFE is worth the extra cost when your application demands chemical resistance above 200°C, coefficient of friction below 0.10, or chemical compatibility that POM and PEEK cannot provide. For most applications, cheaper alternatives like POM or nylon deliver adequate performance at lower cost.
Discover when PTFE is the right choice, how its softness affects design, and when cost-effective plastics can meet performance needs without compromise.
Table of Contents
Can Cheaper Plastics Meet My Performance Requirements?
Use POM or nylon if your operating temperature stays below 120°C, chemical exposure is limited to oils and weak acids, and you don’t need ultra-low friction. PTFE costs 2-3x more and requires longer lead times—only specify it when alternatives will fail your application.
Here’s the reality check: POM handles brake fluid, hydraulic oil, gasoline, and isopropyl alcohol without degradation. Per ASTM D543 testing, POM maintains 95% tensile strength after 30-day exposure to these fluids. It fails when exposed to strong acids (battery acid), caustics (sodium hydroxide), or chlorinated solvents where tensile strength drops 40% within 24 hours.
We’ve seen product failures when engineers chose POM for chemical pump seals exposed to concentrated sulfuric acid—the parts cracked within 48 hours. Conversely, audio manufacturers often over-specify PTFE for control knobs that only see occasional alcohol cleaning, adding unnecessary cost when FDA-approved POM delivers identical performance with Ra 1.6 μm surface finish verified by profilometer measurement.
Quick decision criteria: Choose PTFE if your application involves continuous temperatures above 150°C, strong acids/bases, or requires coefficient of friction below 0.15. For general mechanical components, fasteners, or housings with mild chemical exposure, POM saves 50% on material cost with ±0.02 mm tolerances confirmed through CMM inspection.
Design Takeaway: Test your specific chemicals against POM first—most applications don’t need PTFE’s premium performance. Reserve PTFE for genuine chemical compatibility or extreme temperature requirements where failure isn’t acceptable.
When Does PTFE's Low Friction Beat POM or Nylon?
Choose PTFE when your application requires coefficient of friction below 0.15 or operates over 10,000 cycles without lubrication. POM delivers 0.20-0.35 friction coefficient per ASTM D1894—adequate for most assemblies with periodic lubrication.
We’ve machined PTFE valve stems for pneumatic actuators cycling 50,000+ times where POM alternatives seized after 15,000 cycles, causing system failures. Surface analysis showed POM galling at contact points while PTFE maintained Ra 3.2 μm finish throughout testing.
Quick cycle estimation: Count expected daily operations × operating days × safety factor of 3. Example: 50 daily cycles × 365 days × 3 = 54,750 cycles annually—use PTFE. Under 5,000 annual cycles with lubrication access? POM works fine.
Red flags for POM failure:
- Visible wear particles or dust around moving parts
- Increasing operating force or sticking motion
- Surface scoring or discoloration on sliding surfaces
If you’re within 20% of the 10,000-cycle threshold or operating in contamination-sensitive environments, choose PTFE for safety margin.
Design Takeaway: PTFE’s low friction justifies cost only in high-cycle, dry-running, or contamination-critical applications. Most mechanical assemblies with lubrication access perform adequately with POM at lower system cost.
Can PTFE Replace Metal Bushings in My Design?
PTFE replaces metal bushings when loads stay below 1,000 psi and you need corrosion resistance or electrical isolation. Above 2,000 psi, PTFE exhibits permanent deformation while bronze maintains dimensional stability per ASTM D695 compression testing.
Simple load calculation: Force (lbs) ÷ bearing area (in²) = pressure (psi). Example: 500 lb load on 0.75″ diameter bushing = 500 ÷ 0.44 = 1,136 psi—marginal for PTFE. Add 50% safety margin: if calculated load exceeds 650 psi, consider metal bushings.
We’ve replaced bronze bushings in chemical metering pumps where corrosive fluids attacked metal—PTFE eliminated galvanic corrosion while maintaining ±0.05 mm bore tolerance verified by CMM inspection over 12 months.
Warning signs PTFE is overloaded:
- Visible compression or “mushrooming” at bearing edges
- Increased clearances or play in assembly
- Permanent indentation marks from shaft contact
Design Takeaway: PTFE successfully replaces metal bushings in low-load, corrosive, or electrically sensitive applications. High-stress mechanical systems require metal bushings despite maintenance overhead.
What's the Risk of Part Failure if I Don't Use PTFE?
Choosing POM over PTFE risks chemical attack, thermal degradation, or friction wear when conditions exceed POM’s limits. Consequences range from gradual performance loss to catastrophic failure depending on application criticality.
Simple compatibility test: Submerge a POM sample in your actual chemical for 24 hours at operating temperature. Measure dimensional change and check for surface crazing—over 5% swelling or visible cracking means switch to PTFE.
We’ve documented semiconductor equipment failures when POM seals contacted cleaning solvents—swollen seals caused vacuum leaks, contaminating $50,000+ wafer batches. Temperature failures occur above 120°C where POM loses dimensional stability per ASTM D638 testing.
Design transition strategy: Start with POM for prototypes if unsure—switching to PTFE later requires minimal design changes but adds 2-3 weeks to production schedule and 40-60% material cost increase.
Design Takeaway: Match material selection to failure consequences—specify PTFE when degradation creates safety risks or expensive damage. Accept cheaper alternatives when gradual performance loss is manageable through maintenance.
How Does PTFE's Softness Affect My Part Design?
PTFE’s low durometer (Shore D 50-65) limits minimum wall thickness to 0.030″ and requires support for spans over 2″ to prevent deflection. Design generous radii and avoid sharp internal corners that concentrate stress and cause cracking during machining.
Thin-wall challenges are real: PTFE parts under 0.025″ thick distort during clamping, making ±0.005 mm tolerances impossible to hold. We machine PTFE housings with 0.040″ minimum walls using soft-jaw fixtures and reduced clamping pressure—thinner sections require custom tooling that adds 30-40% to machining cost.
Critical design limits for PTFE:
- Minimum wall thickness: 0.030″ (0.76 mm)
- Unsupported spans: Maximum 2″ without mid-support
- Internal corner radii: Minimum 0.010″ to prevent stress concentration
Sharp corners create stress risers where PTFE tears during machining. Food processing equipment requires 0.020″ radii minimum for cleanability—sharp corners trap contamination and fail FDA inspection. However, PTFE’s softness enables complex geometries impossible with harder plastics, including undercuts and flexible living hinges.
Fixturing considerations: Standard vise pressure deforms PTFE parts. Vacuum fixtures or custom soft-jaws add 1-2 days to setup but ensure dimensional accuracy. Parts over 4″ length require multiple support points to prevent sagging.
Design Takeaway: Design PTFE parts with generous wall thickness, supported geometry, and filleted corners. Its softness enables complex shapes but requires careful attention to structural support and machining fixtures.
What Tolerances Should You Specify for PTFE Components?
Standard PTFE tolerances are ±0.005″ (±0.13 mm) for critical dimensions and ±0.010″ for non-critical features. Tighter tolerances to ±0.002″ are achievable but require specialized fixtures, temperature control, and increase machining time by 50-75%.
PTFE’s thermal expansion coefficient (100 × 10⁻⁶/°C) means a 4″ part grows 0.002″ with 10°C temperature change. We machine PTFE components in climate-controlled environment at 20°C ±2°C to maintain consistent dimensions. Post-machining annealing relieves internal stress but can cause ±0.001″ dimensional shift per ASTM D1044 guidelines.
Chemical processing equipment often specifies ±0.002″ on sealing surfaces where leakage creates safety hazards. However, over-tolerancing PTFE increases cost significantly—reserve tight specs for functional surfaces only. ISO 2768-f (fine) class applies unless tighter control needed for mating features or pressure boundaries.
Tolerance selection guide: Use ±0.010″ for clearance fits and non-critical dimensions. Apply ±0.005″ for assembly interfaces and bearing surfaces. Reserve ±0.002″ only for sealing surfaces, pressure boundaries, or precision mating features where function depends on tight control.
CMM inspection at controlled temperature required for tolerances under ±0.005″—standard calipers lack accuracy for PTFE’s soft surface that compresses under measurement force, giving false readings.
Design Takeaway: Apply ±0.005″ standard tolerance for PTFE components, reserving ±0.002″ only for critical sealing or mating surfaces. Account for thermal expansion in tolerance stack-ups and specify annealing requirements clearly on drawings.
Conclusion
PTFE justifies its premium cost when chemical resistance, temperature stability, or ultra-low friction exceed what POM and nylon can deliver. For most applications, cheaper alternatives provide adequate performance with easier machining. Match material selection to actual performance requirements, not theoretical specifications. Contact us to explore PTFE manufacturing solutions tailored to your product requirements.
Frequently Asked Questions
±0.005″ (±0.13 mm) standard, ±0.002″ achievable with climate control and specialized setup. Tighter tolerances increase machining time 50-75%. Account for ±0.001″ shift if post-machining annealing required.
Yes, with minimal design changes. Switching adds 2-3 weeks to production schedule and 40-60% material cost increase. Consider PTFE initially if operating near POM’s chemical or temperature limits.
0.030″ (0.76 mm) minimum for reliable machining without distortion. Thinner walls require specialized soft-jaw fixtures and increase machining cost by 30-40%. Standard clamping pressure deforms walls under 0.025″ thick.
Test first. POM handles oils, weak acids, and alcohols but fails with strong acids, bases, or chlorinated solvents. Submerge POM sample in your chemical for 24 hours—over 5% swelling means switch to PTFE.
No. PTFE works up to 1,000 psi while POM handles 2,000+ psi before permanent deformation. PTFE’s advantage is corrosion resistance and low friction, not load capacity. Use load calculation: Force ÷ bearing area.
PTFE material costs 2-3x more than POM, plus 40-60% higher machining time due to specialized fixturing and slower feeds. Total part cost typically 3-4x higher than equivalent POM component.
