scholarly journals Sorption/Diffusion Contributions to the Gas Permeation Properties of Bi-Soft Segment Polyurethane/Polycaprolactone Membranes for Membrane Blood Oxygenators

Membranes ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 8
Author(s):  
Tiago M. Eusébio ◽  
Ana Rita Martins ◽  
Gabriela Pon ◽  
Mónica Faria ◽  
Pedro Morgado ◽  
...  
Keyword(s):  
Steady State ◽  
Soft Segment ◽  
Time Lag ◽  
Transient State ◽  
Gas Permeation ◽  
Dominant Factor ◽  
Atmospheric Gases ◽  
Equilibrium Conditions ◽  
Permeability Coefficients ◽  
Permeation Properties

Due to their high hemocompatibility and gas permeation capacity, bi-soft segment polyurethane/polycaprolactone (PU/PCL) polymers are promising materials for use in membrane blood oxygenators. In this work, both nonporous symmetric and integral asymmetric PU/PCL membranes were synthesized, and the permeation properties of the atmospheric gases N2, O2, and CO2 through these membranes were experimentally determined using a new custom-built gas permeation apparatus. Permeate pressure vs. time curves were obtained at 37.0 °C and gas feed pressures up to 5 bar. Fluxes, permeances, and permeability coefficients were determined from the steady-state part of the curves, and the diffusion and sorption coefficients were estimated from the analysis of the transient state using the time-lag method. Independent measurements of the sorption coefficients of the three gases were performed, under equilibrium conditions, in order to validate the new setup and procedure. This work shows that the gas sorption in the PU/PCL polymers is the dominant factor for the permeation properties of the atmospheric gases in these membranes.

Gas Permeation Properties of Poly(N-Vinylpyrrolidone)/ 3-Aminopropyltriethoxysilane Hybrid Membranes

2007 ◽  
Vol 124-126 ◽  
pp. 683-686 ◽  
Author(s):  
Kyoung Mi Jang ◽  
Jun Seok Kim ◽  
Sung Koo Lee ◽  
Hyun Joon Kim
Keyword(s):  
Gas Permeability ◽  
Diffusion Mechanism ◽  
Sol Gel ◽  
Gas Permeation ◽  
Hybrid Membranes ◽  
Positive Dependence ◽  
Chain Flexibility ◽  
Permeability Coefficients ◽  
Increasing Temperature ◽  
Permeation Properties

The organic-inorganic hybrid membranes of poly(N-vinylpyrrolidone) (PVP) and 3- aminopropyltriethoxysilane (APTEOS) were prepared by sol-gel process and their permeation properties of N2 and O2 were studied. The gas permeability coefficients of N2 and O2 are increased with increasing temperature in a range of 30-50°C. The positive dependence on temperature and higher ideal separation factor than theoretical Knudsen value indicates that PVP/APTEOS hybrid membranes follow solution-diffusion mechanism, which is applied to nonporous membrane. The permeability coefficients of N2 and O2 are decreased with increasing PVP content, at a given temperature. It can be explained that the stronger interaction between PVP and APTEOS reduces available free volume, although the increasing of PVP content may lead to an enhancement of chain flexibility.

scholarly journals Gas Permeation Properties of High-Silica CHA-Type Zeolite Membrane

Membranes ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 249
Author(s):  
Yasuhisa Hasegawa ◽  
Chie Abe ◽  
Mayumi Natsui ◽  
Ayumi Ikeda
Keyword(s):  
Molecular Size ◽  
Gas Permeation ◽  
Zeolite Membrane ◽  
Type Zeolite ◽  
High Silica ◽  
Separation Of Co2 ◽  
Α Al2o3 ◽  
Separation Performances ◽  
Molecular Sieving ◽  
Permeation Properties

The polycrystalline CHA-type zeolite layer with Si/Al = 18 was formed on the porous α-Al2O3 tube in this study, and the gas permeation properties were determined using single-component H2, CO2, N2, CH4, n-C4H10, and SF6 at 303–473 K. The membrane showed permeation behavior, wherein the permeance reduced with the molecular size, attributed to the effect of molecular sieving. The separation performances were also determined using the equimolar mixtures of N2–SF6, CO2–N2, and CO2–CH4. As a result, the N2/SF6 and CO2/CH4 selectivities were as high as 710 and 240, respectively. However, the CO2/N2 selectivity was only 25. These results propose that the high-silica CHA-type zeolite membrane is suitable for the separation of CO2 from CH4 by the effect of molecular sieving.

scholarly journals Multi-Machine Repairable System with One Unreliable Server and Variable Repair Rate

Mathematics ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 1299
Author(s):  
Shengli Lv
Keyword(s):  
Steady State ◽  
Transient State ◽  
Repairable System ◽  
Repair Rate ◽  
Numerical Illustration ◽  
Transform Method ◽  
Unreliable Server ◽  
Busy Time ◽  
The Mean ◽  
Mean Time

This paper analyzed the multi-machine repairable system with one unreliable server and one repairman. The machines may break at any time. One server oversees servicing the machine breakdown. The server may fail at any time with different failure rates in idle time and busy time. One repairman is responsible for repairing the server failure; the repair rate is variable to adapt to whether the machines are all functioning normally or not. All the time distributions are exponential. Using the quasi-birth-death(QBD) process theory, the steady-state availability of the machines, the steady-state availability of the server, and other steady-state indices of the system are given. The transient-state indices of the system, including the reliability of the machines and the reliability of the server, are obtained by solving the transient-state probabilistic differential equations. The Laplace–Stieltjes transform method is used to ascertain the mean time to the first breakdown of the system and the mean time to the first failure of the server. The case analysis and numerical illustration are presented to visualize the effects of the system parameters on various performance indices.

scholarly journals The Effect of Extrusion Conditions and Material Properties on the Gas Permeation Properties of LDPE/LLDPE Silage Wrap Films

2005 ◽  
Vol 21 (1) ◽  
pp. 27-38 ◽  
Author(s):  
Gerry M. McNally ◽  
Christopher Laffin ◽  
P. D. Forristal ◽  
Padraig O’Kiely ◽  
Christopher M. Small
Keyword(s):  
Material Properties ◽  
Gas Permeation ◽  
Permeation Properties
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