For several years, one of the biggest drawbacks of “chemically resistant” FFKMs, or perfluoroelasters, has been their relatively poor compression set resistance. Typically, compounding these materials to be extremely resistant to many different chemical environments comes with the drawback of having to give up their ability to resist taking a set after being under high temperatures for an extended period. Parker's solution to this industry challenge is ULTRA FF156.
Compression set refers to a common failure mode of elastomers where a seal permanently flattens out while in application and the joint begins to leak. A material's resistance to this permanent deformation can be easily tested in the lab. To do so, a seal’s thickness is measured, then that seal is compressed about 25% before being heated in an oven at a particular temperature for a predetermined amount of time. That seal is then removed from the oven and the thickness is remeasured.
The value reported is “% seal height not recovered”, therefore a lower value would imply a higher compression set resistance. Figure 1, seen below, shows how FF156 compares to other chemically resistant FFKM offerings within the same hardness range and class. As you can see, FF156 vastly outperforms both in compression set resistance which implies longer seal life in application.
When looking at relative value and cost of material, FF156 is an excellent choice within the FFKM material family. It demonstrates a higher temperature capability and broader chemical resistance compared to FKMs, silicones, and AFLAS. The higher temperature capability of FF156 allows it to be used for applications in aerospace, heavy duty mobile, chemical processing, and semiconductor industries where temperatures can routinely exceed 400°F. A snapshot of FF156’s chemical resistance is shown in Figure 1, with the low volume swell in an Ethylene Diamine fluid immersion. Ethylene Diamine is a very aggressive base and is used as a common benchmark to test fluid for FFKM chemical resistance. Additionally, FF156 demonstrates above average hot water and steam resistance for an FFKM compound. Outside of FF580 and FF582, Parker’s explicit “steam resistant FFKMs”, it has the best steam resistance within the material family. Finally, FF156 can be manufactured into a variety of custom molded, extruded, spliced, O-ring or lathe cut products. This versatility allows a uniform compound offering for the Parker ULTRA FFKM family of products.
FF156 offers a wide variety of features, including high compression set resistance, broad chemical resistance, and steam resistance, at approximately 60% of the cost of FF580, widely considered to be one of the top-performing 75 duro FFKMs in its class. Coupled with the ability to be extruded, spliced, or molded into complex shapes, FF156 is Parker’s newest solution to your sealing needs.