Density membrane

Millet determined self-diffusion coefficients for Na and Cs+ ions in hydrated 1200 EW membranes using conductivity measurements and the Einstein equation, D+ = u+kT, where u+ is the absolute mobility of the given cation. u+ can be derived from the equivalent conductivity according to A = 0+IC+ = Fu+, where 0+ is the specific conductivity, C+ is the cation concentration (calculated on the basis of the dry membrane density, EW, and the water content), and F is the Faraday constant. The values of D+ determined via these conductivity measurements... 

Real membrane density (g/cm ) dynamic viscosity of the gas (Pa s) osmotic pressure at membrane surface (cm/s) fluid viscosity membrane lifetime (year)... 

In the case of diffusion of a substance through a stationary solid or semisolid phase such as the polymeric network of a membrane, it is convenient to view the stationary phase as a fixed reference and to consider only the flux of mobile molecules, namely dmg or external solvent. Assuming that the diffusion processes do not imply important variations of membrane density [50] and that no convective flux is present (this is the most common situation met in practice when dealing with membranes),... 

Membrane Density Porosity = 1 - Density Polymer Density = 1.370 g/cm ... 

Ni-Al203 membrane Density (g/cm ) Diameter Shrinkage (%) Thickness shrinkage(%)... 

The molar concentrations of the membrane components can be calculated if the membrane volume is known. It can be determined by measuring the membrane geometric dimensions or by using the membrane density determined independently and knowing the membrane mass. In PIM extraction and transport studies, emphasis is placed on achieving high extraction constants and transport rates and separation from other species present in the aqneous phase. 

Another possible approach to indirectly characterize the membrane morphology is based on the investigation of the free volume within the matrix. Density measurements [119,120] and positron annihilation lifetime spectroscopy evaluation [47] are common methods. Typically, the comparison between the theoretical density or free volume (calculated by simple additivity rules) and the experimental one can reveal the presence of a good interfacial morphology or the presence of interface voids or clustering formation. Fig. 7.13 shows the influence of filler content on the morphology of poly(trimethylsilyl propyne) (PTMSP)/Ti02 NCMs in terms of the volumetric fraction of interface voids as calculated from a comparison of the expected and measured membrane density [119],... 

As water swells the membrane, we assume the partial molar volume of water plus the partial molar volume of the dry membrane adds to the total membrane volume per mole. If M w is the equivalent weight of the dry membrane, Mw (18 gm/mol) is the mass per mole of water, is the dry membrane density, the mass per equivalent of the swelled membrane is, and... 

Every PVC membrane can absorb water from the water phase, which causes turbidity of membrane. This phenomenon was studied by Harrison et a/. [31,32]. It was found that water is not evenly distributed in the membrane, but there exists a water-rich area near the electrode surface. The water content in a typical PVC membrane (33% PVC, 67% bis(2-ethylhexyl) adipate (DOA)) is approx. 0.6 w/w the membrane density is 1.08 g/cm This value is approximated, since it depends on the membrane composition (hydrophilic components will cause higher adsorption of water) and the concentration of ions (ionic strength) in the water phase. 

The layer structure is an oversimplified model, since the membranes also have a lateral structure. However the real membrane density can be separated into a pure layer structure and a lateral density Ap f ... 

Kubinski, H., Kasper, C. B. Interactions between carcinogens and microsomal membrane Change in membrane density and in its ability to bind nucleic acids. Science... 

PLA membranes with different crystalline structures were prepared by regulating the heating and cooling conditions during membrane preparation [1], Thermally induced crystallization of PLA membranes was conducted by casting under vacuum for 48 hours at 70°C, 80°C, 90°C, and 150°C. The thermally treated PLA membranes were then cooled to room temperature under atmospheric pressure. The properties of the PLA membranes prepared in the study of Sawada et al. are summarized in Table 3.1 [1]. The membrane density increased from 1.257 to 1.273 g cm" as the treatment temperature increased from 70°C to 150°C. 

The membrane density of these PLA membranes is snnunarized in Table 3.3. The sample preparation conditions of the PLA products significantly inflnenced their man-brane densities. The literature indicates that PLA manbranes have density valnes ranging from 1.248 to 1.27 g cm [9,16-18]. The density of the nonimmersed amorphons PLA membrane in this study was 1.257 g cm", which falls within the range reported in the literature [2]. Type I and Type 11 membranes had densities of approximately 1.257 g cm". However, the densities of Type III membranes decreased, ranging from 1.241 to 1.252 g cm". The membranes that swelled more had lower densities. The densities of Type IV membranes sharply decreased, ranging from 0.488 to 0.851 g cm-. ... 

Crystallinity as a function of density is shown in Figure 3.10. The density of Type I and Type II films was 1.257 g cm, which is similar to that of nonimmersed amorphous PLA membranes. Crystallinity does not depend on membrane density at low-range crystallinity (0%-5%). Meanwhile, the crystallinity of Type III PLA membranes was approximately 25% at membrane densities, ranging from 1.242 to 1.257 g cm. Density slightly decreased with increasing crystallinity. The crystallinity of... 

FIGURES.10 Membrane density as a function of crystallinity under DSC. (Reprinted from S. Sato et al, Effects of various liquid organic solvents on solvent-induced crystallization of amorphous poly[lactic acid] film, Journal of Applied Polymer Science, 2013, 129, 1607-17. Copyright Wiley-VCH Verlag GmbH Co. KGaA.)... 

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