Gas impermeability

N. Moroni, G. Calloni, and A. MarcotulUo. Gas impermeable carbon black cements analysis of field performances. In Proceedings Volume, volume 2, pages 781-792. E P Forum et al Offshore Mediter Conf (OMC 97) (Ravenna, Italy, 3/19-3/21), 1997. 

In contrast to the exterior localization of cutin, suberin can be deposited in both external and internal tissues. External deposition occurs in the periderm of secondary roots and stems and on cotton fibers, whereas internal deposition occurs in the root endodermis and the bundle sheath of monocots. The Casparian strip of the root en-dodermis contains suberin, which produces a barrier isolating the apoplast of the root cortex from the central vascular cylinder. Suberin also produces a gas-impermeable barrier between the bundle sheath and mesophyll cells in C4 plants. The bark of trees contains periderm-derived cork cells that have a high suberin content. 

PP/EPDM-V better elasticity and good thermal resistance PP/NBR-V same elasticity plus oil resistance PP/IIR-V same elasticity plus gas impermeability TPU high mechanical properties... 

The structure of the rice root is therefore apparently dominated by the need for internal gas transport. On the face of it, this structure may conflict with the needs for efficient nutrient absorption (Kirk and Bouldin, 1991). The development of gas-impermeable layers in the root wall seems likely to impair the ability of those parts of the root to absorb nutrients, and the disintegration of the cortex might impair transport from the apoplasm to the main solute transport vessels in the stele, though these points are uncertain (Drew and Saker, 1986 Kronzucker et al, 1998a). It seems likely that the short fine lateral roots are responsible for the bulk of the nutrient absorption by the root system and compensate for any impairment of nutrient absorption by the primary roots as a result of adaptations for internal aeration. 

Outstanding oil and solvent resistance, good gas impermeability, resistance to aging, ozone, bad odors, low tensile strength, poor heat resistance... 

Gas, or vapor molecules, after the degasitication process, can go through the pore structure of crystalline and ordered nanoporous materials through a series of channels and/or cavities. Each layer of these channels and cavities is separated by a dense, gas-impermeable division, and within this adsorption space the molecules are subjected to force fields. The interaction with this adsorption field within the adsorption space is the base for the use of these materials in adsorption processes. Sorption operations used for separation processes imply molecular transfer from a gas or a liquid to the adsorbent pore network [2],... 

In an SOFC, the electrochemical reactions take place in the electrodes in the functional layer, that is, a zone within a distance of less than 10-20 pm from the electrolyte surface [5,136-138], The portion of the electrode beyond this width is principally a current collector structure, which has to be porous to permit the admission of gas to the functional layer where the oxidation and reduction reactions occur. Besides, the electrolyte has to be gas impermeable to avoid direct combination and combustion of the gases [137], The essential parts of the SOFC, that is, the electrolyte, the anode, and the cathode, are made of ceramic materials produced with appropriate electrical conducting properties, chemical and structural stabilities, similar expansion coefficients, and negligible reactivity properties [135],... 

Currently, the most widely applied electrolyte in PEFCs is Nation, manufactured by DuPont, Dow Chemical, Midland, MI, USA and other chemical companies. The Nation polymer electrolyte is a good proton conductor. Besides, it has very low electron conductivity, and is gas impermeable in order to provide the necessary spatial separation between the anode oxidation and the cathode reduction reactions. 

Acrylonitrile (AN), C3H3N, first became an important polymeric building block in tlie 1940s. Although it had been discovered in 1893 (1), its unique properties were not realized until the development of nitrile rubbers during World War II (see Elastomers, synthetic, nitrile rubber) and the discovery of solvents for the homopolymer with resultant fiber applications (see Fibers, acrylic) for textiles and carbon libers. As a comonomer, acrylonitrile (qv) contributes hardness, rigidity, solvent and light resistance, gas impermeability, and the ability to orient. These properties have led to many copolymer application developments since 1950. 

Acrylonitrile lias contributed the desirable properties of rigidity, high temperature resistance, clarity, solvent resistance, and gas impermeability to many polymeric systems. Its availability, reactivity7, and low cost ensure a continuing market presence and provide potential for many new applications. 

Ethylene oxide forms explosive mixtures in air at concentrations ranging from. f to 80% by volume. The explosion hazard is eliminated when the gas is mixed with sufUeicnt concentrations of carbon dioxide. Carhoxide is a commercial sterilant containing 10% ethylene oxide and 9()%> carbon dioxide by volume that can be handled and released in air without danger of explosion. Sterilization is aeeompiishcd in a sealed, autoclave-like chamber or in gas-impermeable bags. 

The electrolyte has to have a high conductivity at operating temperature, that is, it should cause a low ohmic drop (<0.15 2/cm2). It should have negligible electronic conductivity, be gas impermeable, and chemically stable in an oxidative and reductive environment (1.2 and 0.0 V, respectively). 

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