Accession Number : AD0733467

Title :   The Properties of Water in Capillary Systems.

Descriptive Note : Technical rept.,

Corporate Author : HYDRONAUTICS INC LAUREL MD

Personal Author(s) : Frommer,Moshe A. ; Lancet,Doron ; Shporer,Mordechai

Report Date : OCT 1971

Pagination or Media Count : 31

Abstract : The relative amounts of freezing and non-freezing water in various cellulose acetate (CA) membranes have been determined by differential scanning calorimetry. It has been found that: A significant fraction (17-40 percent) of the water (1.0-3.1 g H2O per g dry CA) in any membrane does not freeze at temperatures as low as -40C. The amount of non-freezing bound water (0.4-0.7g non-freezing water per g dry CA) depends upon the nature of the membrane, and is significantly higher than the total amount of water (all of which is non-freezing) absorbed from liquid water by a dense film of the same polymer (about 0.18g water per g dry CA). The structures of the membranes have been studied by scanning-electron-microscopy. The results suggest that the amounts of non-freezing water in cellulose acetate membranes decrease with the increase in the packing density (compactness) of polymer within the membrane. NMR techniques proved to be a powerful tool for studying freezing processes of water in membranes. The amounts of water contained in a wet membrane equilibrated with water vapors at 90 percent R.H. was approximately, twice that adsorbed on a freeze-dried membrane under identical equilibration conditions. The amount of non-freezing water in a wet membrane (representing equilibration at 100 percent R.H.) is approximately equal to the amount of water present in an identical membrane. (Author)

Descriptors :   (*CELLULOSE ACETATES, MEMBRANES), (*MEMBRANES, *FREEZING), (*WATER, *ADSORPTION), ICE, NUCLEAR MAGNETIC RESONANCE, CALORIMETRY, ELECTRON MICROSCOPY, SURFACE PROPERTIES, FILMS, POLYMERS

Subject Categories : Physical Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE