Fluoroelastomer and Perfluoroelastomer Compatibility with Advanced Gas Turbine Lubricants

The progression of gas turbine engine design encompasses a relentless drive towards more powerful, higher thrust, lighter weight, fuel efficient engines, with accompanying reductions in noise and emissions, as well as better reliability, operating safety and longer time on wing. These trends converge to push engine thermodynamics to their limits, invariably culminating in higher operating temperatures. As a result, engine builders have adopted advanced lubricants with higher thermo-oxidative stability (HTS), in order to achieve long life engine performance. These HTS oils are proving to be significantly more aggressive towards standard fluoroelastomers. As a result, there is a gradual migration to specialty grades that offer significantly improved compatibility with HTS oils. As temperatures have escalated, higher performance perfluoroelastomers have found greater use in aircraft engines. Selection and adoption is primarily a result of their ability to deliver outstanding seal performance in hot air and lube oils. In this presentation the compatibility of selected fluoroelastomers and perfluoroelastomers with commercial gas turbine engine lubricants will be discussed. Fluoroelastomers that have historically been used will be compared to several new specialty types that display improved resistance to HTS oils. In addition, several perfluoroelastomers demonstrating superior compatibility to HTS turbine oils will be reviewed. Testing will characterize physical properties and property retention in lube oil through 2000 hours at 200°C and 232°C. Properties relevant to sealing applications will be discussed and best in class for each type of material will highlighted. In gaining a better understanding of the respective capabilities of these high performance fluorinated elastomers, the engineer may design more robust sealing systems.