To address the water management problem in proton-exchange membrane
fuel cells, porous graphite composites were prepared by incorporating
sacrificial pore-forming agents in the blend of graphite and a phenolic
resin formed into a flat plate using compression molding. Sucrose
was found to be an effective porogen in the porous plate production
process. The effects of relative amounts of graphite, polymer, and
porogen in the composite were studied. Bipolar plate properties such
as the water uptake by wicking and vacuum infusion, gas-breakthrough
pressure across the water-infused pores, electrical conductivity,
and flexural strength of the plates were measured and correlated with
the plate composition. The plate porosity was evaluated by determining
the masses of dry and water-infused plates in air and under water.
The porosity, ε, showed a linear increase with an increase in
the porogen concentration in the range of 0–10%. The permeabilities, K, of water through the graphite plates with different porosity
values were calculated by measuring the water flux over a range of
pressures. The water permeability increased with oxidation and hydrophilization
of the pore surface. Dynamic water contact angle measurements were
used to characterize the effect of chemical and thermal treatments
on the water wettability of the plates. The gas-breakthrough pressure
of the water-infused plates was found to be linearly correlated with
the parameter,
, proportional to the capillary pressure
of the gas–water interface of surface tension, γ, and
contact angle, θ. Porous plates capable of a total water uptake
greater than 25 wt %, with the gas-breakthrough pressure higher than
10 psi, through-plane electrical conductivity exceeding 100 S cm–1, and flexural strength exceeding 25 MPa were obtained.