Technical Article

Common O-ring Sealing Materials and Their Hydraulic Application Characteristics (Two) - Fluororubber

Fluororubber is a synthetic rubber containing fluorine atoms. With its excellent high-temperature resistance, chemical corrosion resistance, oil resistance, and aging resistance, it has become an indispensable sealing, shock absorption, and medium resistant material in high-end industrial fields. Common universal FKM (such as GFLT, G-21) and low-temperature modified FKM (such as GLT-S, LT-805).  

1. Main advantages:

(1) Excellent high temperature resistance: Long term use temperature of -20°C ~200°C (short-term up to 230 °C), it is the rubber with the best heat resistance in hydraulic systems.

(2) Excellent chemical/medium resistance: It has excellent resistance to almost all petroleum based hydraulic oils and various organic solvents.

(3) Extremely low permeability/low swelling: Especially suitable for environments with heavy water vapor or fire-resistant media such as HFD-R that absorb heat and are easily hydrolyzed.

(4) Excellent ozone/weather resistance: almost unaffected by atmospheric aging.

(5) Good mechanical performance.

(6) Low compression permanent deformation.

(7) Good high-temperature wear resistance.  

2. Main disadvantages:

(1) High cost: several times or even more than ten times that of NBR.

(2) Poor low-temperature performance (especially universal type): Standard FKM significantly hardens and becomes brittle below -20 °C, loses elasticity, and experiences a sharp decline in dynamic sealing performance (TR10 is approximately -15 °C).

(3) Slightly swollen for certain ester/ether based synthetic oils, such as certain poly (alpha olefin) oils and special ester lubricants.

(4) Low temperature flexibility is poor, and the processing technology is relatively complex.  

3. Typical hydraulic applications:

(1) Sealing for all high-temperature environments: hydraulic components near the engine, hot press, extruder, braking system, aerospace hydraulic system.

(2) Systems using phosphate ester fire-resistant oil and alcohol based aviation fluid: must be used.

(3) High pressure (>25 MPa) dynamic seal: Provides better high-temperature extrusion resistance and wear resistance than NBR (but still requires a retaining ring).

(4) High requirement static sealing: The primary requirement for system reliability is in critical locations where long-term maintenance is inconvenient or longer service life is needed.

(5) Sealing in contact with multiple chemical media: For example, maintenance equipment may come into contact with sealing points of different oils and solvents.