Gasket materials, properties

TABLE 28-28 Important Properties of Gasket Materials Concluded)... 

Rubber (straight) To 600 See Gasket Materials for properties. Mainly used for ring-type seals, although some types are available as spiral packings. 

The product ( Teflon ) is a solid, chemically inert substance that is stable to around 300°. It makes excellent electrical insulation and gasket materials. It also has self-lubricating properties, which are exploited in the preparation of low-adhesion surfaces (such as nonstick fry pans) and light-duty bearings. 

D. Indium. Indium (mp I57°C), is a soft metal which wets many surfaces and retains its ductility at very low temperatures. This combination of properties makes indium an excellent gasket material between dissimilar materials. For example, a gasket made of indium wire will give a vacuum-tight seal between... 

Piston-cylinder devices rely on the compression of the sample itself to generate the pressure. In opposed-anvil systems, in contrast, the decrease in volume, and therefore the maximum pressure, is limited by the flow of deformable gaskets in various geometries. Thus, the starting geometry in such devices usually is critical it depends on the maximum desired pressure and on the mechanical properties of the sample and the gasket materials. 

Gaskets and other seals are required for use in many applications where adjacent surfaces are to be sealed to prevent fluid or gas leakage [81]. Composite gasket materials made by a wet laid process are comprised of a fiber component which is distributed within an elastomeric binder matrix, together with property improving solid fillers [82]. 

The values in Table are for ambient conditions oniy The gasket material selection is based on the design temperature and the process conditions. The properties for seating and seaiing of the gasket should be based on the ambient properties. 

Polyurethanes, 57, 62, 119-26 basic reactions, 120-22 catalysts, 124 chain extenders, 124 development of a new specification, 157 foams, 125, 135, 187 foam core in high speed train cab, 192 isocyanate, 120, 122 materials, 122 perlon, 121 polyols, 123 polyesters, 123 polyethers, 123 in printed gaskets, 149 properties, 125... 

Besides the bipolar plate, the gasket material is an important component of the fuel cell stack and tends to be heavily underestimated. It plays a key role in the mechanical properties of the stack, compensated tolerances and partially determines the mechanical compression of the MEA. Inappropriately selected gasket materials may cause failure of the MEA or fracture of the bipolar plates. Despite the fact that the gasket has only to seal the stack, it is a highly challenging issue due to the tolerances of the other components which have to be managed. And last but not the least, the gasket has to be cost attractive. 

Additionally, the gasket material has to be resistant to the selected coolant under operating conditions. Since some rubber composites contain carbon fillers to improve their mechanical properties, unintended electrical conductivity of the material needs not be ruled out. It has to be noted that the values mentioned above are for orientation and refer to standard elastomer materials available on the market. 

Table 19.3 Gasket material overview with physical properties...

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