After extrusion, a flat sheet is recovered from the calender
and passed through a set of corrugating rolls to reach its
final pattern, and thus, the overall thickness is achieved
without the need of ribs. The corrugated separators are
available in two different wave designs: type ‘‘S’’ is sinusoidal
(Fig. 1), whereas type ‘‘T’’ is straight and vertical
(Fig. 2). The overall thickness achieved by the flat sheet
rolling process can range from 0.9 to 5.0 mm. The thickness
of the preliminary flat sheet is proportional to the required
overall thickness of the corrugated product. Therefore, the
backweb of the corrugated separator increases slightly
with the overall product thickness as illustrated in Table 1
(0.48 mm backweb for a 1.20 mm ‘‘S’’ separator compared
to 0.70 mm backweb for a 4.0 mm ‘‘T’’ separator). Note that
for certain applications, a glassmat can be laminated to one
side of the corrugated product, as for standard ribbed
separators.