Applications of PTFE gaskets
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From what I’ve read, it seems that PTFE gaskets are really excellent. Aside from temperature and pressure limitations, what types of media cannot be handled with PTFE gaskets? Are there any other classifications for modified PTFE gaskets? Who can explain it in detail? 3Q
It cannot be used in environments with strong corrosive agents; PTFE can only withstand mild corrosion
Suitable media for polyperfluoroethylene FEP (F46): any organic solvent or reagent, dilute or concentrated inorganic acids, bases, alkanes, aromatics, chlorinated hydrocarbons, etc. Operating temperature: -85~150. Features: Its mechanical, electrical properties and chemical stability are essentially the same as those of F4, but its key advantage is high dynamic impact toughness, along with excellent weathering and radiation resistance. Polytrifluoroethylene PCTEF (F3): Suitable media: various organic solvents, inorganic corrosive liquids (oxidizing acids). Operating temperature: -195 to 120°C. Features: Its heat resistance, electrical properties, and chemical stability are second only to those of F4; its mechanical strength, creep resistance, and hardness are better than those of F4. Polypropylene: RPP. Suitable media: aqueous solutions of inorganic salts, as well as dilute or concentrated solutions of inorganic acids and bases. Operating temperature: -14~80. Features: One of the lightest plastics; it has superior yield, tensile, and compressive strengths as well as hardness compared to low-pressure polyethylene. It offers excellent rigidity, good heat resistance, is easy to mold, and is cost-effective. Modified dynamic impact resistance, fluidity, and bending elasticity. Polyvinyl chloride: Rigid PVC. Suitable media: water, concentrated alkalis, non-oxidizing acids, alkanes, oils, and ozone. Operating temperature: 0-55. Features: high mechanical strength, excellent chemical stability and dielectric properties, good oil resistance and aging resistance, easy to weld and bond, and low cost. Media suitable for polytetrafluoroethylene PTFE (F4): strong acids, strong bases, strong oxidizing agents, etc. Operating temperature: -200~180. Features: It possesses excellent chemical stability, high heat and cold resistance, a very low friction coefficient, making it an excellent self-lubricating material. However, its mechanical properties are poor, its fluidity is low, and it experiences significant thermal expansion. Polyvinylidene chloride PVDF(F2): Medium used: Resistant to most chemicals and solvents. Operating temperature: -70~100. Features: Better tensile strength to compressive strength ratio than F4; resistant to bending, weathering, and radiation. It is resistant to light and aging, etc.; its main advantages are good toughness and easy formability. Polyolefins: PO. Suitable media: acids, bases, salts at various concentrations, and certain organic solvents. Operating temperature: -58~80. Features: It is currently the most ideal anti-corrosion material in the world, and is widely used as a lining for large-scale equipment and pipe components manufactured by rotational molding.
I rarely use PTFE gaskets. In my industry, where there is no corrosion and the pressure levels are moderate, I use flexible graphite gaskets. Metal wound gaskets are more commonly used. Of course, PTFE gaskets can also be used in low-pressure applications, but one issue is the cost of these gaskets (PTFE is likely more expensive than graphite). The most important problem is that once a PTFE gasket is compressed and takes its shape, it cannot be reused!
Who says it can only be used in mildly corrosive environments? Polytetrafluoroethylene remains inert to most chemicals and solvents, and it can withstand strong acids, strong bases, water, and various organic solvents.
Modified PTFE gaskets: It depends on what purpose you intend to use them for. The most common types that are modified are fiberglass gaskets, copper powder gaskets, black PTFE gaskets (usually with additives such as graphite, and sometimes carbon fiber as well), and so on.