Elastomeric Lining

FIG. 10-56 Single- rotor screw pump with an elastomeric lining. CouHesy of Moyno Tump Division, Rohhins [Pg.912]

FIG. 14.15 Single-rotor screw pump with elastomeric lining. (From Perry, R.H., Chilton, C.H., and Kirkpatrick, S.D., Chemical Engineers Handbook, 4th ed., McGraw-Hill, New York, 1963.)... 

Elastomeric linings play an important role in industry where their resistance to highly corrosive environments allow many processes to be carried out in an economic manner. Major areas of use include heavy chemicals, dyestuffs, pharmaceuticals, electroplating, fertilisers, steel, fo stuffs, ore extraction, hydrometallurgical extraction of elemental metals and the water treatment industry. 

Both natural and synthetic rubbers are used as elastomeric linings. The most commonly used synthetic elastomers are NBR (acrylonitrile-butadiene), Hypalon (chlorosulfonated polyethylene), EPDM (ethylene-propylene-diene monomer), EPT (ethylene-propylene-diene terpolymer), SBR (styrene-butadiene), and neoprene (polychloroprene). A maximum use temperature of nS F/SOX is typical. 

The thicker lines represent the sequences of hard urethane segments, and the clusters of these effectively act as crosslinks, making the material act as a conventional elastomer. When the temperature is raised high enough, the clusters disassociate and the material can be made to flow when subsequently cooled, the clusters can reform and the material again exhibits elastomeric properties. Thus these materials show elastomeric behaviour at room temperature, but can be processed as thermoplastics. Hence the name of the material class - thermoplastic elastomers. 

It is possible to explain the decrease of ZnCFO efficiency as component of various vulcanization systems for rubbers of general and special assignment in the earlier submitted line (fig. 10) also by character of formed morphology of compositions. So, at use of ZnCFO as the activator of sulfur vulcanization the structure of rubbers with the minimal value of parameter r is formed, and at transition from sulfur to peroxide vulcanization of elastomeric compositions the particles size of heterophase is increased (fig. 11 b). 

ZnCFO is the effective vulcanization active component of the sulfur, thiuram, peroxide and metaloxide vulcanization systems for isoprene, nitrile-butadiene and chloroprene rubbers at the same time it is not effective in resin vulcanization system for butyl rubber. On a degree of positive influence on the properties of elastomeric compositions vulcanization systems with ZnCFO are arranged in a line ... 

Even though there is no specific pharmacopeial prescription for testing these materials, they should present the same profile stipulated for container and closures. In the case of tubing lines, which are also made of elastomeric materials, an extractabihty test for elastomeric closures is recommended, mainly for those made of PVC. 

Various organic dihalides are employed in a reaction with sodium polysulfide to produce organic polysulfides (Thiokols). Ethylene dichloride, from the direct chlorination of ethylene, dichloroethyl formal, and /3,0 -dichlorodiethyl ether are the principal dihalides that have been employed in the process (44). These elastomeric polymers have been commercially available for a number of years, and many applications have been developed for them. They have excellent oil resistance and one of their principal uses has been in hose and tank linings in which that property is required. 

Running loss emissions are emissions from the fuel tank during vehicle operation due to heating of the fuel, losses from the evaporative canister, or losses due to permeation of fuel through elastomeric fuel lines. 

For suction pump systems where the potential for syphoning exists should the fuel feed line be broken when the dispenser is in operation, some jurisdictions require a valve that allows fuel flow from the tank only when the dispenser is in operation. These valves are typically made from brass and have an elastomeric diaphragm used to open the valve. The diaphragm within the valve must be methanol-compatible or it will rupture, causing the pump to draw air and lose prime. The valves should be nickel-plated and the diaphragm replaced with one made from teflon [4.4],... 

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