Decreased Permeability with "dry" Microcons
When I first starting testing the microcon filters I noticed that if they were allowed to sit overnight (exposed to air) after having been already tested with water the next day if they were tested again the permeability of the membrane decreased significantly.
The membranes come pre-wet with trace amounts of glycerin; spinning with water essentially flushes all the glycerin out of the membrane and thus when it drys the result is a membrane that is not pre-wet. After last weeks tests I let the three membranes that I had tested at 1.35 psi sit open to the atmosphere to allow them to dry completely. I then repeated the same testing procedures and recalculated the hydraulic permeability.
The grouping on the left (1) represents the hydraulic permeability values found during initial testing when the membranes were “fresh out of the box”. The grouping to the right (2) represents the hydraulic permeability of the same membranes found once the glycerin had been removed and the membrane was allowed to dry. Without pre-wetting the hydraulic permeability of the 100K microcon membranes is essentially cut in half.
How do you know that they are shipped with glycerine? Was it stated in the product literature? We have gotten several different stories about whether these need to be pre-wet, so it would be nice to have some documentation…