The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
Donald R Paul - One of the best experts on this subject based on the ideXlab platform.
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feasibility of thermal crosslinking of Polyarylate gas separation membranes using benzocyclobutene based monomers
Journal of Membrane Science, 1997Co-Authors: C T Wright, Donald R PaulAbstract:Abstract Current literature results suggest that crosslinking may be a useful route to balance the productivity/selectivity tradeoff of polymeric gas-separation membranes. This study explores the use of benzocyclobutene chemistry to thermally crosslink Polyarylate membranes based on 1,2-dihydrocyclobutabenzene-3,6-dicarbonyl dichloride (XTA-Cl), fluorene bisphenol (FBP) and 5- t -butyl isophthalic acid dichloride (tBIA). Very high temperatures were required to produce significant crosslinking which also caused significant degradation of the polymers. The result of this heat treatment was small increases in gas-permeability coefficients and small decreases in permselectivity; this is opposite to what is typically observed for simple crosslinking. It is concluded that the thermal treatment required for crosslinking is too severe to utilize this approach successfully for Polyarylate gas-separation membranes.
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Polyarylate gas separation membranes
Macromolecular Symposia, 1997Co-Authors: Donald R Paul, M. R. PixtonAbstract:The molecular design of polymers for membrane separation of gases is illustrated for the oxygen/nitrogen pair by a series of Polyarylates. The use of tetrabromo ring substitutions combined with a fluorene connector group on the bisphenol with or without a t-butyl group on the isophthalic acid monomer leads to state-of-the-art productivity-selectivity combinations.
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gas sorption and transport in uv irradiated Polyarylate copolymers based on tetramethyl bisphenol a and dihydroxybenzophenone
Journal of Membrane Science, 1997Co-Authors: C T Wright, Donald R PaulAbstract:Abstract Gas sorption and transport properties at 35°C are reported for a series of ultraviolet irradiated Polyarylates prepared from tetramethyl bisphenol-A (TMBPA), 4,4′-dihydroxybenzophenone (DHB), and 5-tertiary-butyl isophthalic acid dichloride (tBIA). UV irradiation induces crosslinking and photo-Fries rearrangements in these polymers. The gas permeability of the Polyarylates decreases with UV irradiation due to reductions in the diffusion coefficient; however, the ideal selectivity for all gas pairs increases with UV irradiation. The effect of UV irradiation on the gas transport properties of the Polyarylates is compared with that reported in the literature for similar polyimide materials. The polyimides show much greater improvement in selectivity than do the current Polyarylate materials. The photo-Fries rearrangements limit the amount of crosslinking achievable in these Polyarylate materials in spite of the fact that additional benzophenone units are formed.
Pieter Gijsman - One of the best experts on this subject based on the ideXlab platform.
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photostabilizing of bisphenol a polycarbonate by using uv absorbers and self protective block copolymers based on resorcinol Polyarylate blocks
Polymer Degradation and Stability, 2009Co-Authors: Marjolein M Diepens, Pieter GijsmanAbstract:Bisphenol A polycarbonate degrades due to sunlight, humidity and oxygen. In this study two possible techniques to stabilize the polymer were compared, i.e. blending of UV-absorbers (UVAs) into the polymer or using block copolymers based on resorcinol Polyarylates. Combination of different analysis techniques shows that the protection by UVAs is not as good as by the resorcinol Polyarylate block copolymers. The block copolymer rearranges itself through a photo-Fries rearrangement within hours into a UV-absorbing top layer. Two different block compositions were studied, and the copolymer with the highest concentration of resorcinol Polyarylate groups shows the best protection.
C T Wright - One of the best experts on this subject based on the ideXlab platform.
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feasibility of thermal crosslinking of Polyarylate gas separation membranes using benzocyclobutene based monomers
Journal of Membrane Science, 1997Co-Authors: C T Wright, Donald R PaulAbstract:Abstract Current literature results suggest that crosslinking may be a useful route to balance the productivity/selectivity tradeoff of polymeric gas-separation membranes. This study explores the use of benzocyclobutene chemistry to thermally crosslink Polyarylate membranes based on 1,2-dihydrocyclobutabenzene-3,6-dicarbonyl dichloride (XTA-Cl), fluorene bisphenol (FBP) and 5- t -butyl isophthalic acid dichloride (tBIA). Very high temperatures were required to produce significant crosslinking which also caused significant degradation of the polymers. The result of this heat treatment was small increases in gas-permeability coefficients and small decreases in permselectivity; this is opposite to what is typically observed for simple crosslinking. It is concluded that the thermal treatment required for crosslinking is too severe to utilize this approach successfully for Polyarylate gas-separation membranes.
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gas sorption and transport in uv irradiated Polyarylate copolymers based on tetramethyl bisphenol a and dihydroxybenzophenone
Journal of Membrane Science, 1997Co-Authors: C T Wright, Donald R PaulAbstract:Abstract Gas sorption and transport properties at 35°C are reported for a series of ultraviolet irradiated Polyarylates prepared from tetramethyl bisphenol-A (TMBPA), 4,4′-dihydroxybenzophenone (DHB), and 5-tertiary-butyl isophthalic acid dichloride (tBIA). UV irradiation induces crosslinking and photo-Fries rearrangements in these polymers. The gas permeability of the Polyarylates decreases with UV irradiation due to reductions in the diffusion coefficient; however, the ideal selectivity for all gas pairs increases with UV irradiation. The effect of UV irradiation on the gas transport properties of the Polyarylates is compared with that reported in the literature for similar polyimide materials. The polyimides show much greater improvement in selectivity than do the current Polyarylate materials. The photo-Fries rearrangements limit the amount of crosslinking achievable in these Polyarylate materials in spite of the fact that additional benzophenone units are formed.
Wen-yen Chiu - One of the best experts on this subject based on the ideXlab platform.
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Synthesis of Polyarylate through interfacial polycondensation by use of glycolyzed products of poly(ethylene terephthalate) glycolysis with bisphenol-a
Journal of Polymer Research, 1997Co-Authors: Ding-chang Wang, Chung-yu Wang, Wen-yen Chiu, Leo-wang ChenAbstract:The glycolysis of poly (ethylene-terephthalate) with bisphenol-A at certain ratios of PET/BPA was carried out in an autoclave reactor at different temperatures for varying periods of time. Then the glycolyzed products were utilized together with bisphenol-A for the synthesis of Polyarylates through interfacial polycondensation. The Polyarylates obtained (referred to as b/g-Polyarylates in this article) possess good thermal characteristics but have lower mechanical strength than typical Polyarylate synthesized from pure bisphenol-A by use of the same method. Blending the b/g-Polyarylate with polycarbonate improved the impact strength significantly. As a whole, glycolysis with bisphenol-A followed by synthesis of Polyarylate through interfacial polycondensation provided a feasible route for the reuse of poly(ethylene terephthalate).
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Synthesis of flexible Polyarylate by interfacial polycondensation
Journal of Polymer Research, 1994Co-Authors: Ding-chang Wang, Wen-yen ChiuAbstract:Products with hydroxyl ends were synthesized from the esterification of bisphenol-A, terephthalic acid and ethylene glycol. These ester products were then used for synthesis of Polyarylate by interfacial polycondensation. Not only the relative concentrations of reactants for esterification but also the conditions for interfacial polycondensation, such as the monomer ratio between two phases and the reaction time, play significant roles in affecting the properties of final products. Under proper synthesis conditions, the Polyarylate formed could possess equivalent thermal characteristics and much higher impact strength in comparison with unmodified Polyarylate due to the incorporation of flexible aliphatic segments from ethylene glycol. X-ray diffraction showed the existence of aliphatic segments would induce small degree of orderly alignment locally in structure.
Marjolein M Diepens - One of the best experts on this subject based on the ideXlab platform.
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photostabilizing of bisphenol a polycarbonate by using uv absorbers and self protective block copolymers based on resorcinol Polyarylate blocks
Polymer Degradation and Stability, 2009Co-Authors: Marjolein M Diepens, Pieter GijsmanAbstract:Bisphenol A polycarbonate degrades due to sunlight, humidity and oxygen. In this study two possible techniques to stabilize the polymer were compared, i.e. blending of UV-absorbers (UVAs) into the polymer or using block copolymers based on resorcinol Polyarylates. Combination of different analysis techniques shows that the protection by UVAs is not as good as by the resorcinol Polyarylate block copolymers. The block copolymer rearranges itself through a photo-Fries rearrangement within hours into a UV-absorbing top layer. Two different block compositions were studied, and the copolymer with the highest concentration of resorcinol Polyarylate groups shows the best protection.