Increase In Gas Permeability Research Articles

Decarburization Reaction of Molten Iron of Low Carbon Concentration with Vacuum Suction Degassing Method.

A kinetic study has been made on decarburization reaction of molten iron of low carbon and oxygen concentrations with solid oxides. A new degassing method, namely Vacuum Suction Degassing (VSD) method, was applied to decarburize molten iron to an ultra-low carbon concentration. A porous oxide tube, the inside of which was evacuated, was immersed into molten iron. The initial carbon concentration was varied between 30 and 110 ppm. The initial oxygen concentration was below 50 ppm. The experiments were performed under Ar atmosphere (1.01×105 Pa). The experimental temperature was 1853 K. The VSD method can greatly increase the rate of decarburization of molten iron and the carbon concentration decreases to a very low value of a few ppm. The rate of decarburization with an Al2O3-SiO2 tube is higher than that with an Al2O3 tube. Increase in gas permeability of a porous tube enhances the decarburization reaction. The apparent rate constant of decarburization at the porous tube-molten iron interface with evacuation in the porous tube is about 10 times larger than that without evacuation.

Gas permeation in polycarbonate membranes prepared by the wet-phase inversion method

Polycarbonate (PC) membranes prepared by the wet-phase inversion process was investigated in the present study. Varying amounts of a non-solvent (methanol) were added to the casting solution during membrane preparation and was found to increase significantly membrane porosity. The gas permeability of the PC membranes was increased from 1.68 and 0.26 barrers, respectively, for oxygen and nitrogen without the non-solvent, to 35.1 and 3.86 barrers with 3 ml of the nonsolvent added. The drastic increase in gas permeability was accompanied by only a slight decrease in selectivity. Hence, the PC membranes prepared with addition of methanol have a great potential for industrial oxygen enrichment applications. A simple gas diffusion model with an effective gas diffusion coefficient was found to describe reasonably well the gas permeation process. The estimated effective gas diffusion coefficient can closely reflect the increase in gas permeability of the membranes due to the addition of methanol.

The Selection of Plastic Materials for Blood Bags

The procedures used in the preparation of blood components together with the processes used in the manufacture of multiple blood bag systems impose a unique combination of requirements that severely limits the selection of plastics. Plasticized PVC, the plastic used in the first blood bags introduced by Carl Walter over 40 years ago, remains the material of choice today. Blood bag material research has focused on two areas: (1) the development of containers with increased gas permeability for the storage of platelet concentrates; and (2) the reduction or elimination of plasticizer contamination of stored blood components. This research has led to the development of several second-generation containers that have improved the quality and extended the allowable storage period of platelet transfusion products. Plastics virtually free of extractives are available for the storage of platelets and plasma, but elimination of plasticizers from RBC products has not yet been achieved.

Structure/permeability relationships of siliconcontaining polyimides

The permeability to H 2, O 2, N 2, CO 2, and CH 4 of (1) three silicone-polyimide random copolymers, and (2) two polyimides containing silicon atoms in their backbone chains, was determined at 35.0°C and at pressures up to about 120 psig ( ~ 8.2 atm). The copolymers contained different amounts of BPADA- m-PDA and amine-terminated poly (dimethyl siloxane), and also had different numbers of siloxane linkages in their silicone component. The polyimides containing silicon atoms (“silicon-modified polyimides”) were SiDA-4,4′-ODA and SiDA- p-PDA. The gas permeability and selectivity of the copolymers are more similar to those of their silicone component than of the polyimide component. By contrast, the permeability and selectivity of the silicon-modified polyimides are more similar to those of their parent polyimides. The substitution of SiDA for the PMDA moiety in a polyimide appears to result in a significant increase in gas permeability, without a correspondingly large decrease in selectivity. The potential usefulness of the above polymers and copolymers as gas separation membranes is discussed.

Silicone‐polyethylene blends

AbstractPolyethylene and reactive, high molecular weight polydimethylsiloxanes have been blended under conditions of shear and elevated temperature in order to form uniform, thermoplastic blends. The materials can be extruded, coated on wire, injection molded, or compression molded. Despite the thermoplastic nature, a high gel fraction is present. A structure is proposed consisting of microgelled and grafted particles of silicone dispersed in polyethylene. When compared to pure polyethylene, the blends show lowered modulus over a temperature range of −150 to +65°C increased gas permeability, and lowered mixing energies. Electrical properties include corona resistance superior to polyethylene and a resistance to degradation under conditions simulating those experienced by buried cables superior to typical silicone rubber. Other electrical properties are intermediate between the values observed in the component polymers.