problematic with several fuel system polymers. Researchers
are conducting empirical studies to con;rm compatibility in
many of these instances.
ORNL has conducted exposure studies on test fuels representing gasoline and ethanol in the following volumetric
blends: E10, E17, E25, E50 and E85.
ORNL also has examined gasoline blended with 16 percent and 24 percent isobutanol.
Heavier fuels have included diesel, diesel blended with 20
percent of a fully upgraded bio-oil, (also referred to as pyrolysis
oil or biocrude, the research fuel is made by heating biomass
without oxygen) and a neat bio-intermediate fuel. Both bio-oils
were produced through fast pyrolysis. Fuel types analyzed for
solubility using Hansen solubility parameters include dimethyl
ether, which is a research fuel for use in compression ignition
diesel engines that can be made from biomass, methanol or fossil fuels, and biodiesel. ORNL also has investigated the solubility
of biodiesel as a function of degradation. This study provided
good insight into the observed compatibility behaviors of elastomers exposed to biodiesel and its blends with diesel fuel.
NREL work has focused on functional testing of new and
used equipment at UL and working with industry groups and
refueling manufacturers to develop compatibility documentation. The UL work began with the DOE’s Clean Cities program,
which participated in UL meetings as testing subjects and
standards were developed to address the changing fuel market.
The resulting UL testing subjects — now standards
— (87A for ethanol blends above 10 percent and 87B for bio-diesel blends above 5 percent) require a 15-week soak test with
a percent volume of biofuel followed by performance testing
unique to each equipment type ( 25 percent or 85 percent ethanol; 25 percent or 100 percent biodiesel). (UL 87A and 87B