Permeability Constants

Table 10.6 Vapor Permeability Constants (10 ° P) at 35°Cfor Polymers 10.69...

TABLE 10.5 Gas Permeability Constants (10 P) at 25°C for Polymers and Rubbers The gas permeability constant P is defined as... 

The gas permeability constant is the amount of gas expressed in cubic centimeters passed in 1 s through a 1-cm area of film when the pressure across a film thickness of 1 cm is 1 cmHg and the temperature is 25°C. All tabulated values are multiplied by 10 and are in units of seconds" (centimeters of Hg) k Other temperatures are indicated by exponents and are expressed in degrees Celsius. 

An extensive new Section 10 is devoted to polymers, rubbers, fats, oils, and waxes. A discussion of polymers and rubbers is followed by the formulas and key properties of plastic materials. Eor each member and type of the plastic families there is a tabulation of their physical, electrical, mechanical, and thermal properties and characteristics. A similar treatment is accorded the various types of rubber materials. Chemical resistance and gas permeability constants are also given for rubbers and plastics. The section concludes with various constants of fats, oils, and waxes. 

Table IV. 02, C02, and H20 Permeability Constants of Typical Commercial Polymers at 23°C...

Carbon dioxide permeability constants of commercial polymers 66... 

Pjpp permeability constant measured in Caco-2 or PAM PA assay... 

The gas permeability constants (P) are generally expressed by the amount of the gas at standard temperature and pressure normalized for the thickness, membrane area, time and differential pressure of gas as in the following equation ... 

All symbols are defined at the end of the paper. Equation 10 defines the pure water permeability constant A for the membrane which is a measure of its overall porosity eq 12 defines the solute transport parameter D /K6 for the membrane, which is also a measure of the average pore size on the membrane surface on a relative scale. The Important feature of the above set of equations is that neither any one equation in the set of equations 10 to 13, nor any part of this set of equations is adequate representation of reverse osmosis transport the latter is governed simultaneously by the entire set of eq 10 to 13. Further, under steady state operating conditions, a single set of experimental data on (PWP), (PR), and f enables one to calculate the quantities A, Xy 2> point... 

Membrane Specifications. At a specified operating temperature and pressure, a cellulose acetate membrane is completely specified in terms of its pure water permeability constant A and solute transport parameter D /k6 for a convenient reference solute such as sodium chloride. A single set of experimental data on (PWP), (PR), and f at known operating conditions is enough to obtain data on the specifying parameters A and (DAM/X6)jjg(. 2 at any given temperature and pressure. 

Figure 16. Decrease of separation (or increase of solute permeabilities) of seawater reverse osmosis desalination at several concentration levels of NaOCl. Initial membrane constants pure water permeability constant = 97.0 nmol m Pa s and the solute permeability constant for NaCl = 0.9 X 10 cm s . Operational conditions k = 7.(97 X 10 cm s Ap = 6.0 MPa, and T = 25°C.

The ability of a substance or ion to pass through a membrane typically measured by permeability constants. See Permeability Constant... 

EXTERNAL ION-PAIR RETURN HIDDEN RETURN Ion permeation across membrane, PERMEABILITY CONSTANT PERMEABILITY COEFFICIENT ION PUMPS... 

PERMEABILITY PERMEABILITY CONSTANT MEMBRANE POTENTIAL ACTION POTENTIAL DEPOLARIZATION GOLDMAN EQUATION NERNST EQUATION RESTING POTENTIAL THRESHOLD POTENTIAL PATCH-CLAMP TECHNIQUE Membrane protein dynamics,... 

H. Yasuda, Permeability constants, Section 5 in Polymer Handbook, J. Brandrup and E H. Immergut, eds., Wiley-Interscience, New York (1975). 

Skin penetration rates and permeability constants ( p) for C-labelled diethanolamine (Table 7) were determined in vitro using full-thickness skin preparations from rats, mice, rabbits and humans (female mammoplasty patients). Human skin proved to be the best barrier against aqueous diethanolamine (37%, w/w) followed by rat, rabbit and mouse skin when the chemical was applied as an infinite dose (20 mg/cm to cm of skin for 6 h). The total absorbed dose from aqueous diethanolamine was greater (0.23-6.68%) than that from undiluted material (0.02-1.3%) (Sun et al, 1996). 

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