Hydrophilic polymers dehydration applications

To effectively use ionomer membranes for dehydration applications it is necessary to understand water transport in these polymers. Molecular diffusion in swollen polymers does not follow the classical Fickian behavior. Fickian behavior is observed for diffusion of gases at low pressure through rubbery polymers at temperatures well above Tg. Under these conditions permeability is independent of gas pressure. Glassy polymers show pressure dependent permeabilities. These effects disappear at higher pressures and can be explained by dual mode theory. Similarly, permeabilities of vapors such as water in hydrophobic or mildly hydrophilic membranes are independent of water vapor pressure. 

With sheet hydrogel, the hydrophilic polymers, typically polyacrylamide or polyethylene oxide, are partially cross-linked to form a membrane with sufficient water-holding hydrophilic sites. Typically a hydrogel contains about 96% water. When applied to wound sites such as dermabrasions, minor bums, and skin donor sites, they relieve pain and reduce trauma on both application and removal of the dressings. Hydrogels can be dried to form a dehydrated hydrogel, which has a higher absorption capacity than the hydrated form. 

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