Compatibility Study of Low-Temperature–capable Fluoroelastomers in Jet Fuels

Abstract

A series of four peroxide-cured fluoroelastomer (FKM) samples, varying in fluorine level and low-temperature resistance, were assessed in jet fuels JP-8 and JP-8+100 at 125 °C from 1 to 5 weeks. The key factors were fluorine level, FKM chemical structure, and the jet fuel +100 additive package. FKM stiffened upon aging with a corresponding loss in both tensile and elongation at break properties. Volume swell increased with immersion time, whereas any changes in chemical cross-linking density by equilibrium swelling were minor. The +100 additive package had a mild effect in causing property deterioration through stiffening and volume swell increases. Loss of fluorine from attack at the vinylidene fluoride group by basic additives is likely taking place. Lower fluorine containing FKM with flexible side chains was less affected by the additive package and provided the lowest glass-transition temperature (Tg; approaching −30 °C). The volume swells (<15%) are within the realm of an acceptable material to be in contact with jet fuels.