Selecting the right elastomer and the right seal design is a difficult task. This compatibility guide addresses the ability of the seal material to resist the contacting fluid. Greene Tweed offers a broad range of elastomers, as shown in this guide. Chemraz®, a perfluoroelastomer combining the broad, almost universal chemical resistance of PTFE with the resilience of elastomers, is our most chemically resistant material.
Applying the Compatibility Guide
The ratings contained in this guide result from published data, laboratory soak tests and informed decisions on the part of Greene Tweed personnel. Most ratings are based on ambient temperature, low pressure and 100% concentrations. These ratings could change under different exposure conditions. Real world differences must be recognized when applying laboratory and empirical information to actual field situations. Many factors affect seal performance in actual field conditions. Some elastomer compounds shrink instead of swell in certain fluids. This phenomenon, coupled with high compression set, can result in seal leakage following thermal or pressure cycling. Seals behave differently in dynamic applications than in static conditions. This booklet is only a general guide to the properties of Greene Tweed elastomers. It does not account for differences in the plasticizers that exist between different compounds of the same elastomer. Specific recommendations can only be made when the design and exposure conditions are studied by experienced seal engineers. Whenever in doubt, test for suitability before using, if at all possible. Greene Tweed encourages testing of elastomers before use and will provide test specimens.
Fluorinated products (i.e., Fluoraz®, Fluorosilicone, Viton*, Fluorel** and Chemraz®) should not be exposed to molten or gaseous alkali metals such as potassium or sodium, since an extremely exothermic reaction may occur. (*DuPont trademark, **3M trademark)