Surface morphology changes of hydrophobic Celgard 2500 and Accurel 1E-PP me
mbranes during initial contact with water were examined using scanning elec
tron microscopy (SEM) and image analysis. The surfaces of both membranes sh
owed increases in several of the following morphology parameters after 72 h
of contact: porosity, pore area, pore length, pore breadth, pore equivalen
t diameter and pore spread factor. This was attributed to non-wetting intru
sion of the water meniscus into some pores with a resulting enlargement of
pore entrances. The results also suggested that the larger pores became lar
ger and the smaller pores became smaller. A model based on more effective i
ntrusion of liquid water into the larger pores and a resulting lateral disp
lacement of the fibrils that formed the boundaries with neighbouring, small
er pores was invoked to explain the latter observation. Celgard 2500 membra
ne was also subjected to contact with 30% w/w CaCl2 solution but no signifi
cant morphology change was observed in this medium after 72 h. The absence
of a morphology change was attributed to a lower degree of intrusion of the
CaCl2 solution relative to that of water due to the higher surface tension
of the former. (C) 2000 Elsevier Science B.V. All rights reserved.