Water Impedance of Nitro-cellulose Films

Abstract

Mellon Institute and are tike average results of a number of tests on each type of material. For convenience in calculating heat losses for various mean temperature conditions, the conductivity of a few of these insulations is given in Figure 3. The thickness of insulation required to prevent sweating on the above air duct for any of the insulations whose conductivities are included will be found to be directly proportional to conductivities of the insulations chosen and the insulation used in calculating the table . . In conclusion, the author wishes to express his thanks to R. W. Ortmiller who determined the conductivities of the various insulations. Literature Cited(1) Griffith and Davis, Natl. Phys. Lab., Special Kept. 9 (1922).(2) Heilman, R, H.t Trans. Am. Soc. Meek. EngrsFuels Steam Power, 51, 257 (1929).(3) HotteL H. C" Ibid., 53(19b), 265 (1931).

Permeability of membranes to water vapor with special reference to packaging materials/

“…34 [ [26] 0. 04 [28] 1.1 [26] 2 [28] 22 [2] 44 [1] 68 [20] 150 [26] 1.4 [31] 6 [31] 15 [20] 10 [26] 20 [20] 42 [20] 0. 6 30] 100 [30] 75 [22] 100 [3] 105 [22] 120 [14] 21S [1] 251 [20 336 [14 1, 327 [1] 115 [14] 3.9 6.5 9.6 [23] 126 [20] 130 [14] i The numbers in brackets refer to the list of references at the end of the paper.…”

“…Evidence that such a relation does not hold is found [23], although others have concluded that the relation may or may not hold, depending upon the type of testing method used, the nature of the material, and the effect of sorption at high humidities [26]. Other workers report that the moisture impedance (reciprocal of the permeability) is substantially proportional to the thickness or linearly related to it [31,33].…”

“…Since an increase in moisture transpiration is usually associated with an increase in moisture absorption, we may expect the Von Schroeder effect to have a bearing on the permeability of membranes to water vapor. The testing of materials that do not exhibit the Von Schroeder effect may be simplified by allowing the moisture to enter the membrane from water in direct contact with the membrane [19,31]. Behavior that might be termed a negative Von Schroeder effect has been reported by one investigator [11].…”