Prevailing trends in aircraft turbine engine applications are pushing current elastomeric seal materials to their limits. These trends include the continued drive towards more powerful, lighter weight engines, with accompanying reductions in noise, emissions and fuel consumption, as well as ongoing improvements in reliability, maintainability, and longer intervals between engine overhauls. These trends converge to push engine thermodynamics to their limits, which manifests in higher operating and soakback temperatures. As a result, engine manufacturers specify high temperature stabilized (HTS) oils in order to achieve engine performance and life targets.
Aircraft engine lubricants have had to keep pace with higher operating temperatures while still meeting stringent performance requirements and regulatory and environmental compliance. The demands on lubricant manufacturers include improved thermal oxidative stability, load carrying capability, reductions in vapor phase coking, and environmentally friendly additive systems. In order for oils to be stable at higher temperatures, different and more aggressive base stocks are often used in conjunction with sophisticated packages of surfactants and amine-based stabilizers. It is primarily the additive packages that challenge traditional fluoroelastomers to maintain long life, leak-free sealing performance.
In this paper the compatibility of various fluoroelastomers with commercial jet engine oils will be reviewed. Fluoroelastomers that have historically been used in aerospace sealing applications will be compared to several specialty types. Properties relevant to sealing devices and applications will be discussed. Laboratory testing will characterize physical properties and property retention in jet oil through 1500 hours at 200°C.