The Properties of Water in Capillary Systems.
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)
Document Details
- Document Type
- Technical Report
- Publication Date
- Oct 01, 1971
- Accession Number
- AD0733467
Entities
People
- Doron Lancet
- Mordechai Shporer
- Moshe A. Frommer