ABSTRACT
Before addressing fluid intrusion studies as a way of characterizing filter media and deducing pore-size distributions, let us consider one mechanical model and two mathematical models of random pore-size distributions. The structure of a track-etched membrane is simple. Using high-energy radiation followed by leaching of the damaged tracks, a 10-
µ
m-thick polycarbonate film is drilled with round holes that go straight through. Since the holes are located randomly, the porosity, the ratio of open areas to bulk area, is kept at only 10%. (The diameters of the pores are a function of the leaching time.) Placing more pores would result in overlap, making some extra large pores. Thus, the vast majority of the pores have the same diameter; the pore-size distributions are very narrow. But because the permeabilities of such membranes are low, they are only used for analytical filtration where investigators want to be sure that particles or microbes larger than a certain size are captured.
