Typically magnesium oxide is used to neutralize the resulting hydrofluoric acid and rearrange into magnesium fluoride and water. Ionic crosslinking dihydroxy crosslinking was the next step in curing FKMs.
This combination of high-performance capabilities makes FFKM seals the premium choice for the most challenging applications.
Usually used as a seat, stem packing, diaphragm and gasket. Recent advancements have broadened FDM uses and provide a wider spectrum of properties, such as exceptional tensile strength, tear and compression resistance, and various anti-degradation properties. Dihydroxy aromatic compounds are used as the crosslinking agent and quaternary phosphonium salts are typically used to accelerate the curing process. This modification produces a organophilic clay with a larger interlayer spacing. In contrast to diamine curing the ionic mechanism is not an addition mechanism but an aromatic nucleophilic substitution. Fluroelastomer or FKM is a class of synthetic rubber designed for very high temperature operation. Viton is generally compatible with hydrocarbons , but incompatible with ketones such as acetone and methyl ethyl ketone , ester solvents such as ethyl acetate , amines , and organic acids such as acetic acid. They also have good oil resistance. The first commercially available FFKM seal was produced in the late s. Crosslinking mechanisms[ edit ] There are three established crosslinking mechanisms used in the curing process of FKMs. The higher the fluorine content, the higher the resistance to various fluids. References 9. Automotive: Shaft seals, Check valve balls, Diaphragms, Military flare binders, Electrical connectors, Tire valve stem seals, Clips for jet engines, Lathe cut gaskets etc.
Conclusion FKM is of high value in use as a class of synthetic rubber which provides extraordinary levels of resistance to chemicals, oil and heat.
The moduli and tensile strngths of blend vulcanizates increased with increasing the amount and the cross-linking density of gels, but the elongations decreased.
The mechanical tests were carried out in a Texturometer with 50N load, at room temperature and samples were produced in stripes format with dimensions: 10mm of length, 0. Rooj et al studied [ 1 ] the incorporation of organomontmorillonite OMT in natural rubber to investigate the mechanical reinforcement in the nanocomposites developed.
Chang et al. Viton is generally compatible with hydrocarbonsbut incompatible with ketones such as acetone and methyl ethyl ketoneester solvents such as ethyl acetateaminesand organic acids such as acetic acid.
Fkm chemical compatibility
The Viton fluorocarbon o-rings have similar functional characteristics to Buna-N, but with much higher temperature and chemical resistance characteristics. These bonds also help prevent chemical saturation, and offer limited resistance to steam, methanol, and other highly polar fluids. FKM was originally developed in the late s in response to demand for high performance seals in the aerospace industry. Compression set and low temperature flexibility may be affected negatively. In aerospace, FKM uses include O-rings, shafts, fuel hoses, joints, and other components that help ensure stable operation and performance when subjected to temperature and pressure changes during in-flight conditions. Swelling of vulcanized samples was measured gravimetrically in methyl ethyl ketone MEK , which act as a solvent for FKM. Understanding the differences is critical in helping determine the appropriate sealing solution for your application. O-rings made of Viton are typically color-coded as black, but new gaskets, seals and O-rings should be green FKM or black FKM, but with a green mark on the outer edge. Although rarely used today, diamine curing provides superior rubber-to-metal bonding properties as compared with other crosslinking mechanisms. Today, FKM materials are commonly used to manufacture o-rings, seals, and gaskets for a variety of high-performance applications in the automotive, aerospace, energy, semiconductor, and industrial industries. The nancomposites with 0. The degree of swelling was calculated using Eq. References 9. Type 5 FKM is known for base resistance and high temperature hydrogen sulfide resistance.
based on 97 review