Carbon dioxide permeabilities

Carbon dioxide permeability constants of commercial polymers 66... 

The presence of -S02(OH) groups reduced the carbon dioxide permeability by a factor of three. This can be explained (15) by the decrease in local segmental mobility of the polymer chains due to the interactions arising from hydrogen bonding. However, the overall transport process for this polymer membrane is more complicated and involves a more pronounced discrimination against methane molecules due to the highly polar nature of the polymer. 

The concept of permeability. Pm, described first in Section 4.3.2.2 also applies to membranes. Equation (4.77) relates the permeability to the diffusion coefficient and solubility. Some representative values of permeabilities for common gases in common polymer films are given in Table 4.17. The units of permeability in Table 4.17 are obtained when diffusivity is in units of m /s, and gas solubility is in units of m gas m /(m soUd-N). Note that carbon dioxide permeabilities are generally 3-4 times... 

Carbon Dioxide Permeability, B, and Permeance, II, in the Studied Membranes... 

The effect of plasticizers and temperature on the permeability of small molecules in a typical vinylidene chloride copolymer has been studied thoroughly. The oxygen permeability doubles with the addition of about 1.7 parts per hundred resin (phr) of common plasticizers, or a temperature increase of 8°C (91). The effects of temperature and plasticizer on the permeability are shown in Figure 4. The moisture (water) vapor transmission rate (MVTR or WVTR) doubles with the addition of about 3.5 phr of common plasticizers (92). The dependence of the WVTR on temperature is a litde more complicated. WVTR is commonly reported at a constant difference in relative humidity and not at a constant partial pressure difference. WVTR is a mixed term that increases with increasing temperature because both the fundamental permeability and the fundamental partial pressure at constant relative humidity increase. Carbon dioxide permeability doubles with the addition of about 1.8 phr of common plasticizers, or a temperature increase of 7°C (93). 

Solutions of strong base attack glass and therefore should be stored in polyethylene containets. Polyethylene is slightly permeable to carbon dioxide (permeability constant about 1 X 10 ml-cm/sec-cmS-cm Hg), but no significant carbonate contamination occurs within a reasonable time (see Problem 6-6). 

Solvent-drying. After annealing at lOO C, the absorbed water inside the membranes was removed by a proprietary procedure. Its effect on gas permeation is given in Table VI. No effect is observed on the.helium and carbon dioxide permeability rates. But the permeability rates of nitrogen and methane are considerably lowered so that the separations of both systems, helium/nltrogen and carbon dloxlde/methane, are enhanced. With a value of 44.1 for helium/ nitrogen, the ideal separation factor of the external reference membrane is slightly exceeded, whereas the separation factor for CO2/CK of more than 2500 is Improved by a factor of 600. 

Table 1.5. Water Vapor, Oxygen, Nitrogen, and Carbon Dioxide Permeability through Fluorinated Ethylene Propylene Copolymer...

Figure 1.3 Oxygen and carbon dioxide permeability vs temperature through fluorinated ethylene propylene copolymer.

Figure II.03 Carbon dioxide permeability vs thickness through polyvinylidene fluoride.

High carbon dioxide permeability—so that the liquid membrane it forms allows rapid transfer of carbon dioxide from the blood phase to the bubbles. 

The crystallization of the PLA matrix induces a decrease in the carbon dioxide permeability coefficient [123, 132]. According to Sawada et al, [128] the effect of crystallinity on CO permeability is similar to the one on oxygen, that is to say there is a slight increase in the diffusion coefficient at low crystallinity followed by a decrease of 40%, whereas solubility decreases slowly in relation with the crystallinity degree. 

They must have high oxygen and carbon dioxide permeability. They should be chemically stable without leachable moieties and be blood compatible, minimizing thrombosis, platelet activation and injury, and protein denaturation. 

The presence of a non-hydrophilic lens over the drug delivery system reduced evaporation from the drug plate. However, the oxygen and carbon dioxide permeability of the combined system was lower than that recommended for the safe daily wear of CLs, the CL was too thick to accept, and it proved ineffective at delivering medication for extended periods of time. 

BSI (1997). Paints and Varnishes - Coating Materials and Coating Systems for Exterior Masonry and Concrete Part 6 - Determination of Carbon Dioxide Permeability prEN 1062-6, British Standards Institute London. 

Nakatsuka, S. and Andiady, A. (1994) Studies on enhanced degradable plastics. III. The effect of weathering of polyethylene and (ethylene-carbon monoxide) copolymers on moisture and carbon dioxide permeability. Journal... 

The oxygen permeability of the copolymer membranes varies from 0.17 Barrer to 220 Barrer depending on the membrane composition without a significant loss in selectivity. Fully converted poly(benzoxazole) membranes showed a high carbon dioxide permeability of 1014 Barrer with a CO2/CH4 selectivity of 24 [106]. 

Figure 10.4 Carbon dioxide permeability of [hmim][Tf2N] on cross-linked nylon without CO 5% CO O —> 10ppm CO O 100ppm CO A —>...

Fig. 15.10 Carbon dioxide permeability of the isotropic HPC matrix versus feed pressure [13]...

Unfortunately, except for a few gases in a few glassy polymers, high-pressure sorption and permeation data are not available to pursue the concept of decoupling the thermodynamic and kinetic contributions to the ideal separation factor. The technique, however, can be illustrated for the important case of CO. and CH), for which a fair number of data exist at pressures up to 20 atm. Carbon dioxide permeabilities at 3S°C in a variety of glassy polymers at upstream pressures up to 20 atm (with a negligible downstream pressure) are shown in Fig. 20.3-9. Besides the dramatic range of permeabilities represented (more than a... 

The following results have been obtained for the carbon dioxide permeability in PVC (polyvinyl chloride) at I bar and 10 bar respectively... 

The modified atmosphere packages, with high oxygen and carbon dioxide permeability, give salads or other sorts of vegetables two weeks of shelf life. 

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