The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
Yanmo Chen - One of the best experts on this subject based on the ideXlab platform.
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highly porous fibers prepared by electrospinning a ternary system of nonsolvent solvent poly l lactic acid
Materials Letters, 2009Co-Authors: Zhonghua Qi, Hao Yu, Yanmo ChenAbstract:Abstract In this work, a facile method for fabricating fibers with micro- and nano-porous structure by electrospinning a ternary system of nonsolvent/solvent/poly( l -lactic acid) is presented. Poly( l -lactic acid) (PLLA) was dissolved in a mixture of dichloromethane (solvent) and butanol (nonsolvent) with a certain ratio. During the electrospinning, the evaporation of solvent and nonsolvent would take the composition of polymer fluid jet to enter the two phase region of the ternary phase diagram, since the solvent is more volatile than the nonsolvent. Thus the jet yielded to different phase separated structures, and further evaporation of the residual nonsolvent would lead to porous fibers.
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Highly porous fibers prepared by electrospinning a ternary system of nonsolvent/solvent/poly(l-lactic acid)
Materials Letters, 2009Co-Authors: Zhonghua Qi, Hao Yu, Yanmo ChenAbstract:Abstract In this work, a facile method for fabricating fibers with micro- and nano-porous structure by electrospinning a ternary system of nonsolvent/solvent/poly( l -lactic acid) is presented. Poly( l -lactic acid) (PLLA) was dissolved in a mixture of dichloromethane (solvent) and butanol (nonsolvent) with a certain ratio. During the electrospinning, the evaporation of solvent and nonsolvent would take the composition of polymer fluid jet to enter the two phase region of the ternary phase diagram, since the solvent is more volatile than the nonsolvent. Thus the jet yielded to different phase separated structures, and further evaporation of the residual nonsolvent would lead to porous fibers.
Hideto Matsuyama - One of the best experts on this subject based on the ideXlab platform.
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Solidification characteristics of polymer solution during polyvinylidene fluoride membrane preparation by nonsolvent-induced phase separation
Journal of Membrane Science, 2013Co-Authors: Toru Ishigami, Tatsuo Maruyama, Keisuke Nakatsuka, Yoshikage Ohmukai, Eiji Kamio, Hideto MatsuyamaAbstract:Abstract We investigated the solidification rate of polyvinylidene fluoride (PVDF) membranes during preparation by the nonsolvent-induced phase separation (NIPS) method. A new apparatus for quantitatively measuring membrane stiffness during phase separation was developed. In this apparatus, a polymer solution placed on a stage moves upward and the surface of the polymer solution contacts a sphere attached to the top of a needle. The displacement of a blade spring attached to the needle is then measured by a laser displacement sensor and converted to the surface repulsive force of the polymer solution. The effects of polymer concentration, composition of coagulant, molecular weight of polymer, and addition of hydrophilic additives were investigated. The solidification rate increases with increasing polymer concentration and molecular weight and decreases with the addition of solvent to the coagulation bath. The addition of hydrophilic additives causes rapid uptake of nonsolvent into the polymer solution and had the largest effect on solidification rate. Based on these results, two correlation groups between the solidification rate of the polymer solution and the mechanical strength of the ultimate membrane were identified. This is the first work to directly and quantitatively measure the solidification rate during nonsolvent-induced phase separation.
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preparation of pvdf hollow fiber membrane from a ternary polymer solvent nonsolvent system via thermally induced phase separation tips method
Separation and Purification Technology, 2008Co-Authors: Saeid Rajabzadeh, Tatsuo Maruyama, Tomohiro Sotani, Hideto MatsuyamaAbstract:Abstract Porous poly (vinylidene fluoride) PVDF hollow fiber membranes were successfully prepared from a ternary system including PVDF, solvent and nonsolvent via thermally induced phase separation (TIPS) process. Glycerol triacetate (triacetin) as solvent and glycerol as nonsolvent were used in this study. The effect of nonsolvent concentration on polymer/solvent/nonsolvent phase diagram was studied. The addition of glycerol brought about the change of phase separation mechanisms from the solid–liquid phase separation (polymer crystallization) to liquid–liquid phase separation. Based on these results, hollow fiber membranes were fabricated. Effects of nonsolvent concentration, air gap distance and water bath temperature on morphology, water permeability, solute rejection and strength of fabricated membranes were studied. Using shorter air gap distance, higher bath temperature and higher glycerol concentration were effective to obtain higher water permeability. In another set of experiments, the effect of polymer extrusion temperature on morphology and permeability of the hollow fiber membrane was studied. It was observed that changing polymer extrusion temperature had different effects on membrane permeabilities for both membranes with crystalline and interconnected structures. In addition, the performance of membranes prepared from PVDF/triacetin/glycerol system was compared with that prepared from PVDF/triacetin system.
R. Bhargava - One of the best experts on this subject based on the ideXlab platform.
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FTIR Imaging of Polymer Dissolution. 2. Solvent/Nonsolvent Mixtures
Macromolecules, 2001Co-Authors: T. Ribar, Jack L. Koenig, R. BhargavaAbstract:Fourier transform infrared (FTIR) spectroscopic imaging employing focal plane array (FPA) detection is used to study the dissolution of poly(α-methylstyrene) (PAMS) by solvent solutions containing systematically varied amounts of a nonsolvent. Sequential images were acquired as dissolution proceeded and the samples were not disturbed during image acquisition. Qualitative spatial and chemical distribution of each species within the field of view was obtained by analyzing images based on the characteristic vibrational modes of each species, while quantitative information was gathered through the calculation of individual concentration profiles along the chemical gradient. The images and absorbance profiles showed selective solvent penetration in all cases. In general, the dissolution rate of the polymer decreased linearly with the weight-percent of nonsolvent present in the solution. Anomalously high dissolution rates were observed for solutions containing ∼5−10% nonsolvent. This increase was attributed to ...
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FTIR imaging of polymer dissolution. 2. Solvent/nonsolvent mixtures
Macromolecules, 2001Co-Authors: T. Ribar, J L Koenig, R. BhargavaAbstract:Fourier transform infrared (FTIR) spectroscopic imaging employing focal plane array (FPA) detection is used to study the dissolution of poly(?methylstyrene) (PAMS) by solvent solutions containing systematically varied amounts of a nonsolvent. Sequential images were acquired as dissolution proceeded and the samples were not disturbed during image acquisition. Qualitative spatial and chemical distribution of each species within the field of view was obtained by analyzing images based on the characteristic vibrational modes of each species, while quantitative information was gathered through the calculation of individual concentration profiles along the chemical gradient. The images and absorbance profiles showed selective solvent penetration in all cases. In general, the dissolution rate of the polymer decreased linearly with the weight-percent of nonsolvent present in the solution. Anomalously high dissolution rates were observed for solutions containing ?5-10% nonsolvent. This increase was attributed to the formation of a band of high polymer concentration perpendicular to solvent diffusion direction during the dissolution process. The efficacy of FTIR imaging in studying the spatiotemporal variation of microscopic gradient evolution in multicomponent systems is underscored.
Zhonghua Qi - One of the best experts on this subject based on the ideXlab platform.
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highly porous fibers prepared by electrospinning a ternary system of nonsolvent solvent poly l lactic acid
Materials Letters, 2009Co-Authors: Zhonghua Qi, Hao Yu, Yanmo ChenAbstract:Abstract In this work, a facile method for fabricating fibers with micro- and nano-porous structure by electrospinning a ternary system of nonsolvent/solvent/poly( l -lactic acid) is presented. Poly( l -lactic acid) (PLLA) was dissolved in a mixture of dichloromethane (solvent) and butanol (nonsolvent) with a certain ratio. During the electrospinning, the evaporation of solvent and nonsolvent would take the composition of polymer fluid jet to enter the two phase region of the ternary phase diagram, since the solvent is more volatile than the nonsolvent. Thus the jet yielded to different phase separated structures, and further evaporation of the residual nonsolvent would lead to porous fibers.
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Highly porous fibers prepared by electrospinning a ternary system of nonsolvent/solvent/poly(l-lactic acid)
Materials Letters, 2009Co-Authors: Zhonghua Qi, Hao Yu, Yanmo ChenAbstract:Abstract In this work, a facile method for fabricating fibers with micro- and nano-porous structure by electrospinning a ternary system of nonsolvent/solvent/poly( l -lactic acid) is presented. Poly( l -lactic acid) (PLLA) was dissolved in a mixture of dichloromethane (solvent) and butanol (nonsolvent) with a certain ratio. During the electrospinning, the evaporation of solvent and nonsolvent would take the composition of polymer fluid jet to enter the two phase region of the ternary phase diagram, since the solvent is more volatile than the nonsolvent. Thus the jet yielded to different phase separated structures, and further evaporation of the residual nonsolvent would lead to porous fibers.
T. Ribar - One of the best experts on this subject based on the ideXlab platform.
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FTIR Imaging of Polymer Dissolution. 2. Solvent/Nonsolvent Mixtures
Macromolecules, 2001Co-Authors: T. Ribar, Jack L. Koenig, R. BhargavaAbstract:Fourier transform infrared (FTIR) spectroscopic imaging employing focal plane array (FPA) detection is used to study the dissolution of poly(α-methylstyrene) (PAMS) by solvent solutions containing systematically varied amounts of a nonsolvent. Sequential images were acquired as dissolution proceeded and the samples were not disturbed during image acquisition. Qualitative spatial and chemical distribution of each species within the field of view was obtained by analyzing images based on the characteristic vibrational modes of each species, while quantitative information was gathered through the calculation of individual concentration profiles along the chemical gradient. The images and absorbance profiles showed selective solvent penetration in all cases. In general, the dissolution rate of the polymer decreased linearly with the weight-percent of nonsolvent present in the solution. Anomalously high dissolution rates were observed for solutions containing ∼5−10% nonsolvent. This increase was attributed to ...
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FTIR imaging of polymer dissolution. 2. Solvent/nonsolvent mixtures
Macromolecules, 2001Co-Authors: T. Ribar, J L Koenig, R. BhargavaAbstract:Fourier transform infrared (FTIR) spectroscopic imaging employing focal plane array (FPA) detection is used to study the dissolution of poly(?methylstyrene) (PAMS) by solvent solutions containing systematically varied amounts of a nonsolvent. Sequential images were acquired as dissolution proceeded and the samples were not disturbed during image acquisition. Qualitative spatial and chemical distribution of each species within the field of view was obtained by analyzing images based on the characteristic vibrational modes of each species, while quantitative information was gathered through the calculation of individual concentration profiles along the chemical gradient. The images and absorbance profiles showed selective solvent penetration in all cases. In general, the dissolution rate of the polymer decreased linearly with the weight-percent of nonsolvent present in the solution. Anomalously high dissolution rates were observed for solutions containing ?5-10% nonsolvent. This increase was attributed to the formation of a band of high polymer concentration perpendicular to solvent diffusion direction during the dissolution process. The efficacy of FTIR imaging in studying the spatiotemporal variation of microscopic gradient evolution in multicomponent systems is underscored.
