Fluoroelastomer compound

Parts made from fluoroelastomers ate used ia appHcations that justify their high cost, usually where the maintenance and replacement costs are high enough to offset the initial cost of the part. These include automotive appHcations such as valve stem seals, fuel injector components, radiator, crankcase and transmission seals, and carburetor needle tips. Numerous seals and gaskets in the marine, oilfield, and chemical processing industries employ fluoroelastomers. In addition, many hoses in the automotive and chemical industry are made entirely of fluoroelastomer compounds or have a veneer of the fluoroelastomer as a barrier exposed to the harsh environment. Seals and gaskets in military appHcations and the binder for flares and missile appHcations ate made with fluoroelastomers. 

Figures 10-14 illustrate the reductions obtained in hardness, 50% modulus, 100% modulus, elongation, and tensile strength, respectively, for a fluoroelastomer compound produced under normal production conditions. Table 1 shows the improvement obtained in detail.

Figure 10 Comparison of hardness 3 sigma variability ratings fluoroelastomer compound.

Processing behavior of fluoroelastomers can be improved by the addition of small amounts of plasticizers and processing aids. High-molecular-weight hydrocarbon esters, such as dioctyl phtalate (DOP) and pentaery thritol stearate, are effective plasticizers in fluoroelastomer compounds. Lower-molecular-weight esters also soften... 

Most molds for injection molding are unique in design, which depends on application, fluoroelastomer compound, and feed system (hot or cold runners). Standard systems are distinguished as two plate, three plate, or stack molds [58],... 

Cri-Spersion. [Cri-Tech] Calcium hy-droxide/magnesium oxide/fluorocar-bon elastomer blends activator for fluoroelastomer compounding. 

The general physical and mechanical properties of fluoroelastomers are similar to those of other synthetic rubbers. Fluoroelastomer compounds have good tensile strengths, ranging from 188 to 2900 psi. In general, the tensile strength of any elastomer tends to decrease at elevated temperatures however, loss in tensile strength is much less with the fluoroelastomers. 

A plot was made of the percentage pellet height remaining compared with the pressure applied (see Fig. 4) examining two very good nitrile compounds compared with a number of fluoroelastomer compounds (see Table 6). At a temperature of 200°C the degree of extrusion (loss of pellet height) increases with pressure for all the samples tested. 

The interesting conclusion was that although conventional automotive -type fluoroelastomer compounds were certainly poorer than nitrile, the high-modulus FKM AHV compound performed best of all. Hence, providing proper selection is made, fluorocarbon rubbers can be considered to be at least as good as nitrile in extrusion resistance. 

EFFECT OF STALE" DIESEL OIL ON NITRILE AND FLUOROELASTOMER COMPOUNDS (18 DAYS AT 94°C)... 

Fluoroelastomer compounds, although more costly than most mid-performance elastomers, provide additional value with heat, chemical resistance, and longer seal life. Figure 4.3 expresses the value in use versus the cost per liter (more adapted as part prices are volume based, whereas material prices are mass based). 

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