FFKM (Perfluoroelastomer) is a high-performance synthetic rubber with the following characteristics:
Chemical Structure
Fully fluorinated carbon chain backbone (no hydrogen atoms), structural formula: −(CF2CF2O)�−−(CF2CF2O)n−.
Side chains contain perfluoroalkyl groups, providing extreme inertness.
Key Properties
High-Temperature Resistance: Continuous use up to 327°C, short-term tolerance to 343°C (e.g., Chemours Kalrez® 6375).
Chemical Resistance: Resists 1,600+ chemicals, including strong acids (concentrated H₂SO₄), bases (NaOH), and plasma.
Low Permeability: Gas permeability 10× lower than FKM, ideal for ultra-high vacuum (e.g., semiconductor etching machines).
Mechanical Stability: Compression set <20% (ASTM D395 test).
Applications
Semiconductors: O-rings in wafer processing equipment (resistant to etching gases like Cl₂, NF₃).
Energy: Downhole tool seals (tolerates H₂S, CO₂, 250°C/15,000psi environments).
Aerospace: Sealants for rocket fuel valves (resistant to hydrazine-based propellants).
Comparison with Other Materials
| Property | FFKM | FKM | Silicone |
|---|---|---|---|
| Max Temperature | 327°C | 230°C | 230°C |
| Chemical Resistance | ★★★★★ | ★★★☆☆ | ★★☆☆☆ |
| Cost | Very High ($5000+/kg) | High ($100+/kg) | Low ($20+/kg) |
Limitations
Complex processing: Requires specialized molds and vulcanization techniques.
High cost: Raw material (perfluoroether monomer) synthesis involves multi-step fluorination reactions.