Studies on syntheses and permeabilities of special polymer membranes. II. Permeation characteristics of cellulose nitrate membranes

For the purpose of application in artificial kidneys the permeation characteristics of semipermeable membranes obtained from a system of cellulose nitrate/methyl alcohol/1,4‐dioxane/barium perchlorate were investigated under various conditions. The optimum composition of the casting solution was found to be the proportion cellulose nitrate: methyl alcohol: 1,4‐dioxane as 13:45:42 (wt.‐%). It was found that the permeation rate was influenced by the evaporation period, the maximum permeability lay at 30s. The addition of barium perchlorate to the casting solution increased the permeation rate, especially if more than 60 wt.‐% of barium perchlorate per cellulose nitrate was used. The permeation rate is increasing with the operating pressure, but decreasing with the feed concentration. When several samples of poly(ethylene glycol) having different average molecular weights were used as feed solute, the permeation rate decreased with an increase in average molecular weight. The permeation fraction was 100% in systems of poly(ethylene glycol) with mol. wt. from 200 to 4000 and was 0% in systems of poly(ethylene glycol) 6000 under 200 mm Hg. In blood filtrations the permeation rate of cellulose nitrate membranes had about four‐fold values of cuprophane membranes, and moreover no protein was found in the blood filtrate.