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Cork Composition
Cork composition sheets are produced by grinding cork bark into granules, and bonding with protein or synthetic resin binders into blocks or mats, which are sliced into sheet form. Result is a gasketing material with high compressibility, unusual crush resistance, negligible side flow, good recovery and a high degree of impermeability, under relatively low flange loads.
Widely used for light bolting requirements to seal stamped metal flanges or sealing of easily damaged materials, i.e., glass or ceramics. Cork is impervious to water, lubricating oil and other petroleum derivatives.
Cork sheet primarily used for low internal pressures up to 345 kPa (50 psi), where sustained temperature at the gasket line does not exceed 250°F (120°C). It has poor shelf life and handling characteristics in addition to being dimensionally affected by humidity conditions. It should not be used to seal inorganic acids, alkalies or oxidizing solutions.
Cellular Rubber
Closed cell (expanded) rubber is made from various polymers such as neoprene, EPDM, nitrile & neoprene/ EPDM/SBR blends. The rubber is compounded & expanded into various hardnesses & densities that possess tiny individually sealed cells that resist moisture, dirt and air.
This material can be supplied with or without pressure sensitive adhesive. It is used as gasketing under very light duty applications as well as insulation, sound and vibration damper, also for dust seals to temperatures up to 200ºF.
Plastics
Of all the plastics, PTFE (polytetrafluoroethylene) has emerged as the most common plastic gasket material. PTFE's oustanding properties include resistance to temperature extremes from -423F to 500F. PTFE is highly resistant to chemicals, solvents, caustics and acids except free fluorine and alkali metals. It has a very low surface energy and does not adhere to the flanges. PTFE gaskets can be supplied in a variety of forms either as virgin or reprocessed material and with a variety of filler material such as glass, carbon, molybdenum disulfite, etc. The principal advantage in adding fillers to PTFE is to inhibit cold flow or creep relaxation.
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