
164 HIGH PERFORMANCE POLYMERS
In general, the epoxy resins and the curing agents
in the composite membranes reduce the amount of
available sulfonic acid groups. Thus, the proton con-
ductivity increases.
Therefore, for curing the epoxy groups, special
curing agents, such as, 4,4
-diaminodiphenylsulfone
and 2,2
-benzidinedisulfonic acid, have been used. It
has been demonstrated that 2,2
-benzidinedisulfonic
acid, which bears sulfonic acid groups, can effectively
reduce the loss of proton conductivity in the composite
film [73].
6.5.5 Hydrogen Fuel Cell
Membranes
Sulfonated PEEK polymers have received attention
as a substitute of Nafion® because of their high ...