Fig. 2 shows a non-linear decrease in
the viscosity with increasing temperature due to less intermolecular
interactions at higher temperatures. When the flow curves were
described by the Arrhenius equation, the activation energy which
is an indicator of the sensitivity of a material to temperature
changes, ranged from 15.0 to 20.1 kJ mol1 (data not shown). No
correlation between activation energy and PEM concentrations
was detected.