fluoroelastomer
- March 21, 2017
Gallagher recently released our Introduction to Perfluoroelastomers White Paper, available for download on our site. This was written by Russell Schnell, a current contracted employee of Gallagher Fluid Seals, and more importantly, a former Senior Application Engineer with the Kalrez® perfluoroelastomer parts business at DuPont. The following excerpt is the first section of the White Paper, discussing the history or elastomers and perfluoroelastomers, and the chemistry that helped create these modern materials.
Introduction to the World of Perfluoroelastomers
The use of elastomers is widespread in our world. Elastomers have many uses including: sealing fluids, for tires, in chemical plants, in semiconductor manufacturing equipment, for dust and moisture seals on cell phones, and seals on aircraft engines. The function of the elastomer and technology involved can vary from something as simple as a barrier to rain water, to seals in automobile engines, to critical sealing applications on the Space Station. Selection of the correct elastomer in an application is very important for successful and long term equipment operation. Although many different elastomers exist in the marketplace, when the highest service performance is needed, in terms of chemical and high temperature resistance, the choice is perfluoroelastomers.A perfluoroelastomer can be represented by the letters: FFKM or FFPM (ASTM and ISO designations, respectively). The word itself has two parts, perfluoro (meaning fully fluorinated), and elastomer. Perfluoroelastomers exhibit many properties similar to PTFE (polytetrafluoroethylene), which is also fully fluorinated and considered inert to almost all solvents. PTFE is often referred to as Teflon®, which is a registered trademark of The Chemours Company. PTFE is a plastic, and when compressed, will not recover to its original shape. However, elastomers contain crosslinks, which act as springs to give the material resiliency and the ability to recover after a part has been compressed. This resistance to permanent compression (compression set) gives the material the ability to maintain a seal over time. Finally, while whereas plastics are crystalline, elastomers are amorphous at room temperature; they can be easily compressed and will mold themselves to maintain a seal. Given the chemical structure and performance similarities of FFKMs to PTFE, perfluoroelastomers are sometimes referred to as an elastomeric form of PTFE.