1. PTFE (F4)
✅ Pros: Temperature resistance up to 260°C; superior chemical resistance; moderate cost; can be modified with fillers (graphite/glass fiber/bronze) to improve wear resistance and creep resistance.
❌ Cons: Cannot be melt-processed; products contain micropores; high cold-flow creep; opaque; cannot be heat-welded.
**Typical Applications**
1. Sealing: Gaskets, expanded PTFE (ePTFE) flange gaskets, gland packing, retaining rings, piston rings; filled PTFE used extensively for bushings and sliding blocks.
2. Chemical industry: PTFE-lined steel reactors and piping (steel shell handles pressure).
3. Laboratory: PTFE beakers, stir bars; PTFE films, thread seal tape.
4. Cryogenic conditions: Liquid nitrogen and deep-cryogenic seals.
Not suitable for: Applications requiring transparency, heat welding, or thin-walled precision injection-molded parts.
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2. PFA (Melt-processable PTFE; upgraded version of F46)
✅ Pros: **Temperature resistance matches PTFE but is melt-processable; highly transparent; highest purity; heat-weldable for seamless joints; excellent stress-cracking resistance.**
❌ Cons: Most expensive.
**Typical Applications (Choose PFA for high purity + high temperature)**
1. **Semiconductor wet processing**: Transport of high-purity chemicals, hydrofluoric acid, and ultrapure water; linings for fittings and valves (low metal ion leaching).
2. High-temperature transparent chemical piping (visual monitoring of media required; temperatures >200°C).
3. Pharmaceutical and analytical instrumentation: Sampling lines and chromatography components (low adsorption).
4. Injection-molded parts: Valve diaphragms, precision corrosion-resistant parts; PFA heat welding enables "dead-zone-free" piping systems.
5. High-end films, release films.
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> Key point: PTFE linings contain micropores; high-purity semiconductor applications generally avoid PTFE in favor of PFA.
3. FEP (F46)
✅ Pros: Best processing performance, transparent, cost-effective, suitable for heat-shrink tubing; excellent electrical insulation.
❌ Cons: Long-term max temperature of **200°C** (performance degrades above this); temperature resistance, creep resistance, and purity are inferior to PFA.
**Typical Applications (Temperature ≤200°C; prioritizing transparency + cost-efficiency)**
1. Wire and cable insulation, FEP heat-shrink tubing (high volume)
2. Laboratory transparent tubing, sight-glass piping, standard transparent chemical fittings
3. Standard pharmaceutical and food-grade tubing (temperatures not exceeding 200°C)
4. Lightweight anti-corrosion linings, films
**Not suitable for**: Continuous high-temperature operation above 200°C
Quick Selection Guide by Scenario
1. Seals, gaskets, gland packing, bushings/sliders** → **PTFE (filled/modified)**
2. Semiconductors/high-purity chemicals, high-temp transparent piping, heat-welding required** → **PFA**
3. Cable insulation, heat-shrink tubing, transparent piping (≤200°C), limited budget** → **FEP**
4. Highly corrosive environments (no transparency needed), equipment linings**: High pressure → Steel-lined PTFE; Transparency/welding needed → PFA
5. Temperature >200°C**: PTFE or PFA only; FEP is unsuitable
Summary in Brief
- PTFE: Sintered parts; the primary choice for seals and linings; opaque; cannot be injection molded or welded.
- PFA: A melt-processable, transparent version of PTFE; high-purity, high-temp, premium grade; expensive; the top choice for semiconductors.
- FEP: Cost-effective thermoplastic fluoroplastic; transparent and easy to process; but temperature limit is 200°C.