Low Temperature Capable Fluoroelastomer Compatibility in Jet FUEL

A series of four reference peroxide cured fluoroelastomer (FKM) samples varying in fluorine level and low temperature behaviour have been assessed in jet fuel.    The standard jet fuels tested included JP-8 and  JP-8 +100.   Accelerated immersion aging was undertaken at 125°C  for periods up to 5 weeks.    Aged samples were tested  for hardness, volume swell, and mechanical properties.  Low temperature resistance was inferred through use of dynamic mechanical thermal analysis.

All compounds softened in the early stages of immersion aging and displayed a negative volume swell.  Upon further aging the samples slowly hardened and the volume swell become positive.  This is a normal observation in the degradation of most organic rubbers.  Both tensile strength and elongation to break change, which may start out positive in the beginning of the aging, turned negative and tended towards values of -20% to -35% depending on the FKM compound. Such property losses are generally acceptable for FKM compounds indicating that aging conditions were generally mild.

Within the testing limits applied in this investigation, all four FKM compounds portrayed good resistance to the tested jet fuels.  It appears that higher fluorine content in the FKM caused a more marked effect in observing property loss during immersion aging in spite of lower volume swell. Lower fluorine containing FKMs appear more favorable for overall property retention and have the advantage of providing extra low temperature resistance over standard FKMs.