The composition and design of the material resulting from
this unique manufacturing process have a great influence on
the physical properties of the separator, and especially porosity,
electrical resistance and acid displacement (Table 1).
Generally speaking, separator porosity refers to all the
void spaces existing within the structure of the material. In
the case of silica containing polymeric membranes, two
sources of voids contribute to the overall pore volume: (i) the
silica agglomerate void volume which is the empty space
existing within each silica aggregate (intra-granular porosity)
as well as the space in between different aggregates
(inter-granular porosity), and (ii) the extraction void volume
which results from the extraction of the solvent needed for
the polymer extrusion.