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Santi Kulprathipanja - One of the best experts on this subject based on the ideXlab platform.

  • Effects of novel silane modification of zeolite surface on Polymer Chain rigidification and partial pore blockage in polyethersulfone (PES)-zeolite A mixed matrix membranes
    Journal of Membrane Science, 2006
    Co-Authors: Yi Li, Tai-shung Chung, Huai Min Guan, Santi Kulprathipanja
    Abstract:

    A novel silane coupling agent, (3-aminopropyl)-diethoxymethyl silane (APDEMS) was used in this work to modify zeolite surface for mixed matrix membranes (MMMs). Both elementary analysis and XPS spectra confirm the chemical modification, while BET measurements show no changes in zeolite surface area and total pore volume after the modification. Polyethersulfone (PES)-zeolite 3A, 4A and 5A MMMs were fabricated at high processing temperatures using unmodified and chemical modified zeolite. SEM images of these MMMs indicate the interface between Polymer and zeolite phases becomes better if modified zeolite is used. The effects of chemical modification of zeolite surface and zeolite loadings on the gas separation performance of these MMMs were investigated. Both permeability and selectivity of MMMs made from APDEMS modified zeolite are higher than those of MMMs made from unmodified zeolite at 20 wt% zeolite loading because of a decrease in the degree of partial pore blockage of zeolites. The permeability of all studied gases decreases with increasing zeolite content for PES-zeolite 4A-NH2 MMMs, while for PES-zeolite 5A-NH2 MMMs, the gas permeability decreases and then increases with an increase in zeolite loadings. This unique phenomenon implies that using large pore-size zeolite for MMMs would potentially offset the negative effects of partial pore blockage and Polymer Chain rigidification on permeability. A modified Maxwell model with adjusted parameters was applied to study the PES-zeolite 4A-NH 2 MMM system. The predicted permeability and selectivity show very good agreement with experimental data, indicating the modified Maxwell model is fully capable of predicting the gas separation performance of MMMs made from both unmodified and modified zeolite. © 2005 Elsevier B.V. All rights reserved.

  • the effects of Polymer Chain rigidification zeolite pore size and pore blockage on polyethersulfone pes zeolite a mixed matrix membranes
    Journal of Membrane Science, 2005
    Co-Authors: Yi Li, Tai-shung Chung, Santi Kulprathipanja
    Abstract:

    Abstract The polyethersulfone (PES)-zeolite 3A, 4A and 5A mixed matrix membranes (MMMs) were fabricated with a modified solution-casting procedure at high temperatures close to the glass transition temperatures ( T g ) of Polymer materials. The effects of membrane preparation methodology, zeolite loading and pore size of zeolite on the gas separation performance of these mixed matrix membranes were studied. SEM results show the interface between Polymer and zeolite in MMMs experiencing natural cooling is better (i.e., less defective) than that in MMMs experiencing immediate quenching. The increment of glass transition temperature ( T g ) of MMMs with zeolite loading confirms the Polymer Chain rigidification induced by zeolite. The experimental results indicate that a higher zeolite loading results in a decrease in gas permeability and an increase in gas pair selectivity. The unmodified Maxwell model fails to correctly predict the permeability decrease induced by Polymer Chain rigidification near the zeolite surface and the partial pore blockage of zeolites by the Polymer Chains. A new modified Maxwell model is therefore proposed. It takes the combined effects of Chain rigidification and partial pore blockage of zeolites into calculation. The new model shows much consistent permeability and selectivity predication with experimental data. Surprisingly, an increase in zeolite pore size from 3 to 5 A generally not only increase gas permeability, but also gas pair selectivity. The O 2 /N 2 selectivity of PES-zeolite 3A and PES-zeolite 4A membranes is very similar, while the O 2 /N 2 selectivity of PES-zeolite 5A membranes is much higher. This implies the blockage may narrow a part of zeolite 5A pores to approximately 4 A, which can discriminate the gas pair of O 2 and N 2 , and narrow a part of zeolites 3A and 4A pores to smaller sizes. It is concluded that the partial pore blockage of zeolites by the Polymer Chains has equivalent or more influence on the separation properties of mixed matrix membranes compared with that of the Polymer Chain rigidification.

  • The effects of Polymer Chain rigidification, zeolite pore size and pore blockage on polyethersulfone (PES)-zeolite A mixed matrix membranes
    Journal of Membrane Science, 2005
    Co-Authors: Yi Li, Chun Cao, Tai-shung Chung, Santi Kulprathipanja
    Abstract:

    The polyethersulfone (PES)-zeolite 3A, 4A and 5A mixed matrix membranes (MMMs) were fabricated with a modified solution-casting procedure at high temperatures close to the glass transition temperatures (Tg) of Polymer materials. The effects of membrane preparation methodology, zeolite loading and pore size of zeolite on the gas separation performance of these mixed matrix membranes were studied. SEM results show the interface between Polymer and zeolite in MMMs experiencing natural cooling is better (i.e., less defective) than that in MMMs experiencing immediate quenching. The increment of glass transition temperature (Tg) of MMMs with zeolite loading confirms the Polymer Chain rigidification induced by zeolite. The experimental results indicate that a higher zeolite loading results in a decrease in gas permeability and an increase in gas pair selectivity. The unmodified Maxwell model fails to correctly predict the permeability decrease induced by Polymer Chain rigidification near the zeolite surface and the partial pore blockage of zeolites by the Polymer Chains. A new modified Maxwell model is therefore proposed. It takes the combined effects of Chain rigidification and partial pore blockage of zeolites into calculation. The new model shows much consistent permeability and selectivity predication with experimental data. Surprisingly, an increase in zeolite pore size from 3 to 5 Å generally not only increase gas permeability, but also gas pair selectivity. The O2/N 2 selectivity of PES-zeolite 3A and PES-zeolite 4A membranes is very similar, while the O2/N2 selectivity of PES-zeolite 5A membranes is much higher. This implies the blockage may narrow a part of zeolite 5A pores to approximately 4 Å, which can discriminate the gas pair of O2 and N2, and narrow a part of zeolites 3A and 4A pores to smaller sizes. It is concluded that the partial pore blockage of zeolites by the Polymer Chains has equivalent or more influence on the separation properties of mixed matrix membranes compared with that of the Polymer Chain rigidification. © 2005 Elsevier B.V. All rights reserved.

Yi Li - One of the best experts on this subject based on the ideXlab platform.

  • Effects of novel silane modification of zeolite surface on Polymer Chain rigidification and partial pore blockage in polyethersulfone (PES)-zeolite A mixed matrix membranes
    Journal of Membrane Science, 2006
    Co-Authors: Yi Li, Tai-shung Chung, Huai Min Guan, Santi Kulprathipanja
    Abstract:

    A novel silane coupling agent, (3-aminopropyl)-diethoxymethyl silane (APDEMS) was used in this work to modify zeolite surface for mixed matrix membranes (MMMs). Both elementary analysis and XPS spectra confirm the chemical modification, while BET measurements show no changes in zeolite surface area and total pore volume after the modification. Polyethersulfone (PES)-zeolite 3A, 4A and 5A MMMs were fabricated at high processing temperatures using unmodified and chemical modified zeolite. SEM images of these MMMs indicate the interface between Polymer and zeolite phases becomes better if modified zeolite is used. The effects of chemical modification of zeolite surface and zeolite loadings on the gas separation performance of these MMMs were investigated. Both permeability and selectivity of MMMs made from APDEMS modified zeolite are higher than those of MMMs made from unmodified zeolite at 20 wt% zeolite loading because of a decrease in the degree of partial pore blockage of zeolites. The permeability of all studied gases decreases with increasing zeolite content for PES-zeolite 4A-NH2 MMMs, while for PES-zeolite 5A-NH2 MMMs, the gas permeability decreases and then increases with an increase in zeolite loadings. This unique phenomenon implies that using large pore-size zeolite for MMMs would potentially offset the negative effects of partial pore blockage and Polymer Chain rigidification on permeability. A modified Maxwell model with adjusted parameters was applied to study the PES-zeolite 4A-NH 2 MMM system. The predicted permeability and selectivity show very good agreement with experimental data, indicating the modified Maxwell model is fully capable of predicting the gas separation performance of MMMs made from both unmodified and modified zeolite. © 2005 Elsevier B.V. All rights reserved.

  • the effects of Polymer Chain rigidification zeolite pore size and pore blockage on polyethersulfone pes zeolite a mixed matrix membranes
    Journal of Membrane Science, 2005
    Co-Authors: Yi Li, Tai-shung Chung, Santi Kulprathipanja
    Abstract:

    Abstract The polyethersulfone (PES)-zeolite 3A, 4A and 5A mixed matrix membranes (MMMs) were fabricated with a modified solution-casting procedure at high temperatures close to the glass transition temperatures ( T g ) of Polymer materials. The effects of membrane preparation methodology, zeolite loading and pore size of zeolite on the gas separation performance of these mixed matrix membranes were studied. SEM results show the interface between Polymer and zeolite in MMMs experiencing natural cooling is better (i.e., less defective) than that in MMMs experiencing immediate quenching. The increment of glass transition temperature ( T g ) of MMMs with zeolite loading confirms the Polymer Chain rigidification induced by zeolite. The experimental results indicate that a higher zeolite loading results in a decrease in gas permeability and an increase in gas pair selectivity. The unmodified Maxwell model fails to correctly predict the permeability decrease induced by Polymer Chain rigidification near the zeolite surface and the partial pore blockage of zeolites by the Polymer Chains. A new modified Maxwell model is therefore proposed. It takes the combined effects of Chain rigidification and partial pore blockage of zeolites into calculation. The new model shows much consistent permeability and selectivity predication with experimental data. Surprisingly, an increase in zeolite pore size from 3 to 5 A generally not only increase gas permeability, but also gas pair selectivity. The O 2 /N 2 selectivity of PES-zeolite 3A and PES-zeolite 4A membranes is very similar, while the O 2 /N 2 selectivity of PES-zeolite 5A membranes is much higher. This implies the blockage may narrow a part of zeolite 5A pores to approximately 4 A, which can discriminate the gas pair of O 2 and N 2 , and narrow a part of zeolites 3A and 4A pores to smaller sizes. It is concluded that the partial pore blockage of zeolites by the Polymer Chains has equivalent or more influence on the separation properties of mixed matrix membranes compared with that of the Polymer Chain rigidification.

  • The effects of Polymer Chain rigidification, zeolite pore size and pore blockage on polyethersulfone (PES)-zeolite A mixed matrix membranes
    Journal of Membrane Science, 2005
    Co-Authors: Yi Li, Chun Cao, Tai-shung Chung, Santi Kulprathipanja
    Abstract:

    The polyethersulfone (PES)-zeolite 3A, 4A and 5A mixed matrix membranes (MMMs) were fabricated with a modified solution-casting procedure at high temperatures close to the glass transition temperatures (Tg) of Polymer materials. The effects of membrane preparation methodology, zeolite loading and pore size of zeolite on the gas separation performance of these mixed matrix membranes were studied. SEM results show the interface between Polymer and zeolite in MMMs experiencing natural cooling is better (i.e., less defective) than that in MMMs experiencing immediate quenching. The increment of glass transition temperature (Tg) of MMMs with zeolite loading confirms the Polymer Chain rigidification induced by zeolite. The experimental results indicate that a higher zeolite loading results in a decrease in gas permeability and an increase in gas pair selectivity. The unmodified Maxwell model fails to correctly predict the permeability decrease induced by Polymer Chain rigidification near the zeolite surface and the partial pore blockage of zeolites by the Polymer Chains. A new modified Maxwell model is therefore proposed. It takes the combined effects of Chain rigidification and partial pore blockage of zeolites into calculation. The new model shows much consistent permeability and selectivity predication with experimental data. Surprisingly, an increase in zeolite pore size from 3 to 5 Å generally not only increase gas permeability, but also gas pair selectivity. The O2/N 2 selectivity of PES-zeolite 3A and PES-zeolite 4A membranes is very similar, while the O2/N2 selectivity of PES-zeolite 5A membranes is much higher. This implies the blockage may narrow a part of zeolite 5A pores to approximately 4 Å, which can discriminate the gas pair of O2 and N2, and narrow a part of zeolites 3A and 4A pores to smaller sizes. It is concluded that the partial pore blockage of zeolites by the Polymer Chains has equivalent or more influence on the separation properties of mixed matrix membranes compared with that of the Polymer Chain rigidification. © 2005 Elsevier B.V. All rights reserved.

Tai-shung Chung - One of the best experts on this subject based on the ideXlab platform.

  • Effects of novel silane modification of zeolite surface on Polymer Chain rigidification and partial pore blockage in polyethersulfone (PES)-zeolite A mixed matrix membranes
    Journal of Membrane Science, 2006
    Co-Authors: Yi Li, Tai-shung Chung, Huai Min Guan, Santi Kulprathipanja
    Abstract:

    A novel silane coupling agent, (3-aminopropyl)-diethoxymethyl silane (APDEMS) was used in this work to modify zeolite surface for mixed matrix membranes (MMMs). Both elementary analysis and XPS spectra confirm the chemical modification, while BET measurements show no changes in zeolite surface area and total pore volume after the modification. Polyethersulfone (PES)-zeolite 3A, 4A and 5A MMMs were fabricated at high processing temperatures using unmodified and chemical modified zeolite. SEM images of these MMMs indicate the interface between Polymer and zeolite phases becomes better if modified zeolite is used. The effects of chemical modification of zeolite surface and zeolite loadings on the gas separation performance of these MMMs were investigated. Both permeability and selectivity of MMMs made from APDEMS modified zeolite are higher than those of MMMs made from unmodified zeolite at 20 wt% zeolite loading because of a decrease in the degree of partial pore blockage of zeolites. The permeability of all studied gases decreases with increasing zeolite content for PES-zeolite 4A-NH2 MMMs, while for PES-zeolite 5A-NH2 MMMs, the gas permeability decreases and then increases with an increase in zeolite loadings. This unique phenomenon implies that using large pore-size zeolite for MMMs would potentially offset the negative effects of partial pore blockage and Polymer Chain rigidification on permeability. A modified Maxwell model with adjusted parameters was applied to study the PES-zeolite 4A-NH 2 MMM system. The predicted permeability and selectivity show very good agreement with experimental data, indicating the modified Maxwell model is fully capable of predicting the gas separation performance of MMMs made from both unmodified and modified zeolite. © 2005 Elsevier B.V. All rights reserved.

  • the effects of Polymer Chain rigidification zeolite pore size and pore blockage on polyethersulfone pes zeolite a mixed matrix membranes
    Journal of Membrane Science, 2005
    Co-Authors: Yi Li, Tai-shung Chung, Santi Kulprathipanja
    Abstract:

    Abstract The polyethersulfone (PES)-zeolite 3A, 4A and 5A mixed matrix membranes (MMMs) were fabricated with a modified solution-casting procedure at high temperatures close to the glass transition temperatures ( T g ) of Polymer materials. The effects of membrane preparation methodology, zeolite loading and pore size of zeolite on the gas separation performance of these mixed matrix membranes were studied. SEM results show the interface between Polymer and zeolite in MMMs experiencing natural cooling is better (i.e., less defective) than that in MMMs experiencing immediate quenching. The increment of glass transition temperature ( T g ) of MMMs with zeolite loading confirms the Polymer Chain rigidification induced by zeolite. The experimental results indicate that a higher zeolite loading results in a decrease in gas permeability and an increase in gas pair selectivity. The unmodified Maxwell model fails to correctly predict the permeability decrease induced by Polymer Chain rigidification near the zeolite surface and the partial pore blockage of zeolites by the Polymer Chains. A new modified Maxwell model is therefore proposed. It takes the combined effects of Chain rigidification and partial pore blockage of zeolites into calculation. The new model shows much consistent permeability and selectivity predication with experimental data. Surprisingly, an increase in zeolite pore size from 3 to 5 A generally not only increase gas permeability, but also gas pair selectivity. The O 2 /N 2 selectivity of PES-zeolite 3A and PES-zeolite 4A membranes is very similar, while the O 2 /N 2 selectivity of PES-zeolite 5A membranes is much higher. This implies the blockage may narrow a part of zeolite 5A pores to approximately 4 A, which can discriminate the gas pair of O 2 and N 2 , and narrow a part of zeolites 3A and 4A pores to smaller sizes. It is concluded that the partial pore blockage of zeolites by the Polymer Chains has equivalent or more influence on the separation properties of mixed matrix membranes compared with that of the Polymer Chain rigidification.

  • The effects of Polymer Chain rigidification, zeolite pore size and pore blockage on polyethersulfone (PES)-zeolite A mixed matrix membranes
    Journal of Membrane Science, 2005
    Co-Authors: Yi Li, Chun Cao, Tai-shung Chung, Santi Kulprathipanja
    Abstract:

    The polyethersulfone (PES)-zeolite 3A, 4A and 5A mixed matrix membranes (MMMs) were fabricated with a modified solution-casting procedure at high temperatures close to the glass transition temperatures (Tg) of Polymer materials. The effects of membrane preparation methodology, zeolite loading and pore size of zeolite on the gas separation performance of these mixed matrix membranes were studied. SEM results show the interface between Polymer and zeolite in MMMs experiencing natural cooling is better (i.e., less defective) than that in MMMs experiencing immediate quenching. The increment of glass transition temperature (Tg) of MMMs with zeolite loading confirms the Polymer Chain rigidification induced by zeolite. The experimental results indicate that a higher zeolite loading results in a decrease in gas permeability and an increase in gas pair selectivity. The unmodified Maxwell model fails to correctly predict the permeability decrease induced by Polymer Chain rigidification near the zeolite surface and the partial pore blockage of zeolites by the Polymer Chains. A new modified Maxwell model is therefore proposed. It takes the combined effects of Chain rigidification and partial pore blockage of zeolites into calculation. The new model shows much consistent permeability and selectivity predication with experimental data. Surprisingly, an increase in zeolite pore size from 3 to 5 Å generally not only increase gas permeability, but also gas pair selectivity. The O2/N 2 selectivity of PES-zeolite 3A and PES-zeolite 4A membranes is very similar, while the O2/N2 selectivity of PES-zeolite 5A membranes is much higher. This implies the blockage may narrow a part of zeolite 5A pores to approximately 4 Å, which can discriminate the gas pair of O2 and N2, and narrow a part of zeolites 3A and 4A pores to smaller sizes. It is concluded that the partial pore blockage of zeolites by the Polymer Chains has equivalent or more influence on the separation properties of mixed matrix membranes compared with that of the Polymer Chain rigidification. © 2005 Elsevier B.V. All rights reserved.

Thomas A. Vilgis - One of the best experts on this subject based on the ideXlab platform.

  • thermal breakage and self healing of a Polymer Chain under tensile stress
    Journal of Chemical Physics, 2010
    Co-Authors: A Ghosh, Andrey Milchev, DIPL.-ING. MIREV DIMITROV, Vakhtang G. Rostiashvili, Thomas A. Vilgis
    Abstract:

    We consider the thermal breakage of a tethered Polymer Chain of discrete segments coupled by Morse potentials under constant tensile stress. The Chain dynamics at the onset of fracture is studied analytically by Kramers–Langer multidimensional theory and by extensive molecular dynamics simulations in one dimension (1D) and three dimension (3D) space. Comparison with simulation data in one and three dimensions demonstrates that the Kramers–Langer theory provides good qualitative description of the process of bond scission as caused by a collective unstable mode. We derive distributions of the probability for scission over the successive bonds along the Chain which reveal the influence of Chain ends on rupture in good agreement with theory. The breakage time distribution of an individual bond is found to follow an exponential law as predicted by theory. Special attention is focused on the recombination (self-healing) of broken bonds. Theoretically derived expressions for the recombination time and distance ...

  • Thermal breakage and self-healing of a Polymer Chain under tensile stress
    Journal of Chemical Physics, 2010
    Co-Authors: A Ghosh, Andrey Milchev, DIPL.-ING. MIREV DIMITROV, Vakhtang G. Rostiashvili, Thomas A. Vilgis
    Abstract:

    We consider the thermal breakage of a tethered Polymer Chain of discrete segments coupled by Morse potentials under constant tensile stress. The Chain dynamics at the onset of fracture is studied analytically by Kramers-Langer multidimensional theory and by extensive molecular dynamics simulations in one dimension (1D) and three dimension (3D) space. Comparison with simulation data in one and three dimensions demonstrates that the Kramers-Langer theory provides good qualitative description of the process of bond scission as caused by a collective unstable mode. We derive distributions of the probability for scission over the successive bonds along the Chain which reveal the influence of Chain ends on rupture in good agreement with theory. The breakage time distribution of an individual bond is found to follow an exponential law as predicted by theory. Special attention is focused on the recombination (self-healing) of broken bonds. Theoretically derived expressions for the recombination time and distance distributions comply with MD observations and indicate that the energy barrier position crossing is not a good criterion for true rupture. It is shown that the fraction of self-healing bonds increases with rising temperature and friction.

  • CONFORMATION OF A Polymer-Chain DISSOLVED IN A CRITICAL FLUID
    Journal De Physique Ii, 1993
    Co-Authors: Thomas A. Vilgis, Anne Sans, Gérard Jannink
    Abstract:

    The problem of a Polymer Chain immersed in a critical fluid, e.g. a mixture of low molecular weight solvent close to its critical point, is studied and reformulated in a field theoretic framework. The starting point is a path integral formulation of the Polymer Chain which interacts with the solvent molecules. If the critical solvent is approximated by a Gaussian model all classical results are recovered, i.e. the Polymer Chain collapses close to the critical point. These results become modified at the critical point where non-classical exponents determine the precise form of the fluctuation induced interaction potential between two monomers of the Chain, and so its conformation

A Ghosh - One of the best experts on this subject based on the ideXlab platform.

  • thermal breakage and self healing of a Polymer Chain under tensile stress
    Journal of Chemical Physics, 2010
    Co-Authors: A Ghosh, Andrey Milchev, DIPL.-ING. MIREV DIMITROV, Vakhtang G. Rostiashvili, Thomas A. Vilgis
    Abstract:

    We consider the thermal breakage of a tethered Polymer Chain of discrete segments coupled by Morse potentials under constant tensile stress. The Chain dynamics at the onset of fracture is studied analytically by Kramers–Langer multidimensional theory and by extensive molecular dynamics simulations in one dimension (1D) and three dimension (3D) space. Comparison with simulation data in one and three dimensions demonstrates that the Kramers–Langer theory provides good qualitative description of the process of bond scission as caused by a collective unstable mode. We derive distributions of the probability for scission over the successive bonds along the Chain which reveal the influence of Chain ends on rupture in good agreement with theory. The breakage time distribution of an individual bond is found to follow an exponential law as predicted by theory. Special attention is focused on the recombination (self-healing) of broken bonds. Theoretically derived expressions for the recombination time and distance ...

  • Thermal breakage and self-healing of a Polymer Chain under tensile stress
    Journal of Chemical Physics, 2010
    Co-Authors: A Ghosh, Andrey Milchev, DIPL.-ING. MIREV DIMITROV, Vakhtang G. Rostiashvili, Thomas A. Vilgis
    Abstract:

    We consider the thermal breakage of a tethered Polymer Chain of discrete segments coupled by Morse potentials under constant tensile stress. The Chain dynamics at the onset of fracture is studied analytically by Kramers-Langer multidimensional theory and by extensive molecular dynamics simulations in one dimension (1D) and three dimension (3D) space. Comparison with simulation data in one and three dimensions demonstrates that the Kramers-Langer theory provides good qualitative description of the process of bond scission as caused by a collective unstable mode. We derive distributions of the probability for scission over the successive bonds along the Chain which reveal the influence of Chain ends on rupture in good agreement with theory. The breakage time distribution of an individual bond is found to follow an exponential law as predicted by theory. Special attention is focused on the recombination (self-healing) of broken bonds. Theoretically derived expressions for the recombination time and distance distributions comply with MD observations and indicate that the energy barrier position crossing is not a good criterion for true rupture. It is shown that the fraction of self-healing bonds increases with rising temperature and friction.