What are the commonly used non-metallic materials for valves?

Nitrile Rubber Buna-N
The rated temperature range of nitrile rubber seat is -18℃~100℃. Usually also called NBR, NITRILE, or HYCAR. It is a general-purpose rubber material suitable for water, gas, oil and grease, gasoline (except gasoline with additives), alcohol and ethanol, liquefied petroleum gas, propane and butane, fuel oil and many other media. At the same time, it also has good wear resistance and deformation resistance.
The rated temperature range of food grade (FG) nitrile rubber seat is -18℃~82℃. Its composition complies with CFR Part 21, Section 177.2600. Its scope of use is the same as that of conventional nitrile rubber but requires FDA (US Food and Drug Administration) certification.
Ethylene Propylene Rubber EPDM
The rated temperature range of the ethylene propylene rubber seat is -28°C~120°C. EPDM is the abbreviation of its composition, that is, the terpolymer of ethylene, propylene and alkene, usually also called EPT, Nordell, EPR. Ozone resistance and weather resistance, good electrical insulation performance, good resistance to polar solvents and inorganic media. Therefore, it can be widely used in HVAC industry, water, phosphate ester, alcohol, ethanol, etc. Ethylene-propylene rubber valve seats are not used in hydrocarbon organic solvents and oils, chlorinated hydrocarbons, or other petroleum-based greases.
The rated temperature range of food grade ethylene propylene rubber valve seat is -28℃~120℃. Its composition complies with CFR Part 21, Section 177.2600. Its scope of use is the same as that of conventional nitrile rubber but requires FDA (US Food and Drug Administration) certification.
PTFE
The rated temperature range of PTFE valve seat is -32℃~200℃. Excellent high temperature resistance and chemical corrosion resistance. Because PTFE has high density and excellent anti-permeability, it can also prevent corrosion from most chemical media.
Conductive PTFE is a modified version of PTFE that allows current to pass through the lining thereby eliminating the insulating properties of PTFE. Because of its conductive properties, conductive PTFE cannot be tested for its quality by electric sparks.
Reinforced polytetrafluoroethylene RTFE
RTFE is a modified body of PTFE material. Although the friction coefficient of pure PTFE is very low (0.02~0.04), but the amount of wear, and because of its easy creep, poor mechanical properties, low bearing capacity, poor dimensional stability and other characteristics, its use as a friction material has great limitations. Only modification, the method of material compounding can meet the special requirements of various industries for wear-resistant sealing materials. In terms of improving the wear resistance of PTFE, some wear-resistant substances such as glass fiber, carbon fiber, graphite, molybdenum sulfide, and bronze can be added. powder and some organic compounds, so that they form a network node in the PTFE layered structure, thereby improving stiffness, thermal conductivity, creep resistance, and greatly improving wear resistance.
Viton Viton
The rated temperature of the fluororubber seat is -18°C~150°C. Viton is a registered trademark of DuPont, and Fluorel is a registered trademark of 3M, which is equivalent to fluorine rubber. This material has high temperature resistance and excellent chemical resistance. Suitable for hydrocarbon products, low and high concentrations of mineral acids, but not for steam media and water (poor water resistance).
Ultra High Molecular Weight Polyethylene UHMWPE
The rated temperature range of UHMWPE valve seat is -32℃~88℃. This material has better low temperature resistance than PTFE, but still has excellent chemical resistance. Ultra-high molecular weight polyethylene also has good wear resistance and corrosion resistance, and can be used in high abrasive situations.
Silicon copper rubber Silicone
Silicon-copper rubber is a polymer with organic groups whose main chain is composed of silicon-oxygen atoms. The rated temperature range is -100℃~300℃. It has good heat resistance and temperature resistance, excellent electrical insulation performance and high chemical inertness. Suitable for organic acid and low concentration inorganic acid, dilute alkali and concentrated alkali. Disadvantages: low mechanical strength. After vulcanization is required.
Graphite
Graphite is a crystal of carbon, a non-metallic material with a silver-gray color, soft texture and metallic luster. The Mohs hardness is 1~2, the specific gravity is 2.2~2.3, and its bulk density is generally 1.5~1.8. It has unique physical and chemical properties such as high temperature resistance, oxidation resistance, corrosion resistance, thermal shock resistance, high strength, good toughness, high self-lubricating strength, strong thermal conductivity and electrical conductivity. It has special oxidation resistance, self-lubrication and plasticity at high temperature, and also has good electrical conductivity, thermal conductivity and adhesion. It can be used as a filler or performance improver for rubber, plastic and various composite materials to improve the wear resistance, compression resistance or conductivity of the material. Graphite is usually used to make valve gaskets, packing and valve seats.
The melting point of graphite* is that it begins to soften and tends to melt at 3000°C under vacuum. At 3600°C, graphite begins to evaporate and sublime. The strength of general materials gradually decreases at high temperatures, while graphite is heated to 2000°C. On the contrary, it is twice as high as that at normal temperature, but the oxidation resistance of graphite is poor, and the oxidation rate gradually increases with the increase of temperature.