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Garth L Wilkes - One of the best experts on this subject based on the ideXlab platform.
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structure property relationships of poly urethane urea s with ultra low monol Content poly propylene glycol soft Segments i influence of soft Segment molecular weight and Hard Segment Content
Journal of Applied Polymer Science, 2002Co-Authors: Matthew J Osickey, Bruce D Lawrey, Garth L WilkesAbstract:Structure–property relationships in poly(urethane urea)s synthesized with ultra-low monol Content poly(propylene glycol) soft Segments were investigated as soft Segment molecular weight (2000, 4000, and 8000 g/mol) and Hard Segment Content (6.3 and 9.0 wt %) were varied. Morphological features such as interdomain spacing and interphase thickness were quantified and revealed with small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM). The thermal and mechanical behavior was assessed with a dynamic mechanical analyzer (DMA) and by differential scanning calorimetry (DSC) and stress-strain tests. Hard Segment Content, over the limited range studied, had little effect on the morphology and soft Segment thermal and mechanical properties. The molecular weight of the soft Segments had considerably more influence on the morphology and mechanical properties. Increasing soft Segment molecular weight resulted in greater interdomain spacings, as shown by SAXS, and a noticeable change in the structure, as shown by AFM. Additionally, as soft Segment molecular weight decreased the soft Segment glass transition broadened and rose to higher temperatures. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 229–243, 2002; DOI 10.1002/app.10168
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Structure–property relationships of poly(urethane urea)s with ultra‐low monol Content poly(propylene glycol) soft Segments. I. Influence of soft Segment molecular weight and Hard Segment Content
Journal of Applied Polymer Science, 2002Co-Authors: Matthew J. O'sickey, Bruce D Lawrey, Garth L WilkesAbstract:Structure–property relationships in poly(urethane urea)s synthesized with ultra-low monol Content poly(propylene glycol) soft Segments were investigated as soft Segment molecular weight (2000, 4000, and 8000 g/mol) and Hard Segment Content (6.3 and 9.0 wt %) were varied. Morphological features such as interdomain spacing and interphase thickness were quantified and revealed with small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM). The thermal and mechanical behavior was assessed with a dynamic mechanical analyzer (DMA) and by differential scanning calorimetry (DSC) and stress-strain tests. Hard Segment Content, over the limited range studied, had little effect on the morphology and soft Segment thermal and mechanical properties. The molecular weight of the soft Segments had considerably more influence on the morphology and mechanical properties. Increasing soft Segment molecular weight resulted in greater interdomain spacings, as shown by SAXS, and a noticeable change in the structure, as shown by AFM. Additionally, as soft Segment molecular weight decreased the soft Segment glass transition broadened and rose to higher temperatures. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 229–243, 2002; DOI 10.1002/app.10168
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Exploring macro- and microlevel connectivity of the urea phase in slabstock flexible polyurethane foam formulations using lithium chloride as a probe
Polymer, 2002Co-Authors: Ashish Aneja, Garth L WilkesAbstract:Abstract Urea phase connectivity has been probed by systematically varying the Hard Segment Content, and lithium chloride Content, in a series of plaques based on slabstock flexible polyurethane foams. The plaque formulations are identical to those of slabstock polyurethane foams with the exception that a surfactant is not utilized. Small angle X-ray scattering (SAXS) is used to demonstrate that all materials investigated are microphase separated with similar interdomain spacings, irrespective of Hard Segment Content (21–37 wt%) or LiCl Content. Several complimentary characterization techniques are employed to reveal that urea phase connectivity is present at different length scales. Macrolevel connectivity, or connectivity of the large-scale urea rich aggregates typically observed in flexible slabstock polyurethane foams, is probed using SAXS, TEM, and atomic force microscopy. These techniques collectively show that the urea aggregation increases as the Hard Segment Content is increased. Incorporation of LiCl is shown to systematically reduce the urea aggregation behavior, thus leading to a loss in the macroconnectivity of the urea phase. Wide angle X-ray scattering is used to probe the regularity in Segmental packing, or the microlevel connectivity between the Hard Segments, which is observed to decrease systematically on addition of LiCl. The loss in microlevel connectivity is suggested to increase chain slippage, and leads to increased rates of stress-relaxation for the samples containing LiCl. Materials containing LiCl also display relatively short rubbery plateaus as compared to their counterparts which do not contain the additive. Modulus values, as obtained at ambient conditions by stress-strain analyses, are found to be a stronger function of LiCl Content when the Hard Segment Content is higher.
Jae Whan Cho - One of the best experts on this subject based on the ideXlab platform.
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Water vapor permeability and mechanical properties of fabrics coated with shape‐memory polyurethane
Journal of Applied Polymer Science, 2004Co-Authors: Jae Whan Cho, Byoung Chul Chun, Yong Chae Jung, Yong-chan ChungAbstract:Water vapor permeable fabrics were prepared by coating shape-memory polyurethane (PU), which was synthesized from poly(tetramethylene glycol), 4,4'-methylene bis(phenylisocyanate), and 1,4-butanediol, onto polyester woven fabrics. Water vapor permeability and mechanical properties were investigated as a function of PU Hard-Segment Content or polymer concentration of the coating solution. Water vapor permeability of PU-coated fabrics decreased dramatically with increased concentration of coating solution, whereas only a slight change was observed with the control of PU Hard-Segment Content. The coated fabric showed the clear appearance of a nonporous PU surface according to SEM measurements. Attainment of high water permeability in PU-coated fabrics is considered to arise from the smart permeability characteristics of PU. Mechanical properties of coated fabrics, although there was some variation depending on the concentration of coating solution, were primarily affected by PU Hard-Segment Content. Fabrics coated with PU Hard-Segment Content of 40% showed the lowest breaking stress and modulus as well as the highest breaking elongation, which could be interpreted in terms of the dependency of mechanical properties of coated fabrics on PU Hard-Segment Content and the yarn mobility arising from a difference in penetrating degree of coating solution into the fabric.
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Characterization and mechanical properties of prepolymer and polyurethane block copolymer with a shape memory effect
Fibers and Polymers, 2003Co-Authors: Jae Whan Cho, Byoung Chul Chun, Yong Chae Jung, Sun Hwa Lee, Yong-chan ChungAbstract:The prepolymer and the final polyurethane (PU) block copolymer were synthesized by reacting 4,4-methylene bis(phenylisocyanate) with poly(tetramethylene glycol) and the prepolymer with 1,4-butanediol as a chain extender, respectively, to investigate the relation between phase separation and it’s resulting properties. According to FT-IR data, the phase separation of Hard and soft Segments in the prepolymer and the PU block copolymer grew bigger by increasing the Hard Segment Content, and the PU showed more dominant phase separation than the prepolymer. The heat of fusion due to soft Segments decreased in both the prepolymer and the PU by increasing the Hard Segment Content, whereas the heat of fusion due to Hard Segments increased in the PU did not appear in the prepolymers. The breaking stress and modulus of the prepolymer increased by increasing the Hard Segment Content, and the elongation at break decreased gradually, and the PU showed the highest breaking stress and modulus at 58 % Hard Segment Content. However, the best shape recovery of the PU was obtained at 47 % Hard Segment Content due to the existence of proper interaction among the Hard Segments for shape memory effect. Consequently, the mechanical properties and shape memory effect of the PU were influenced by the degree of phase separation, depending on the incorporation of chain extender as well as the Hard Segment Content.
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structure and thermomechanical properties of polyurethane block copolymers with shape memory effect
Macromolecules, 2001Co-Authors: Bo Sun Lee, Byoung Chul Chun, Yong-chan Chung, And Kyung Il Sul, Jae Whan ChoAbstract:Shape memory polyurethane (PU) block copolymers composed of 4,4‘-methylenebis(phenylisocyanate), poly(tetramethylene glycol), and 1,4-butanediol as a chain extender were synthesized by a two-step process. FT-IR spectra showed that carbonyl peak appearing at 1700 cm-1 increased with higher Hard Segment Content, whereas another carbonyl peak at 1730 cm-1 decreased. It suggests that Hard Segments get more aggregated to form domains in the PU block copolymer as Hard Segment Content increases. Such domain formation has a significant influence on the mechanical and thermomechanical properties of PU, such as maximum stress, tensile modulus, and elongation at break. Especially, maximum stress, tensile modulus, and elongation at break increased significantly at 30 wt % of Hard Segment Content, and the highest loss tangent was observed at the same composition. Heat of crystallization as measured by differential scanning calorimetry is also dependent on the Hard Segment Content. Finally, 80−95% of shape recovery was...
Sung Chul Kim - One of the best experts on this subject based on the ideXlab platform.
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liquid liquid phase separation in a ternary system of Segmented polyetherurethane dimethylformamide water effect of Hard Segment Content
Polymer, 2001Co-Authors: Hwan Kwang Lee, Jy Kim, Yd Kim, Jy Shin, Sung Chul KimAbstract:Abstract A series of Segmented polyurethanes (SPUs) using poly(tetramethylene oxide) (PTMO), 4,4′-methylenebis (phenyl isocyanate) (MDI), and ethylene glycol (EG) with different molar ratios of MDI and PTMO were prepared to study the effects of the Hard Segment Content in SPU on liquid–liquid phase separation in the SPU/dimethylformamide(DMF)/water system. The cloud points were obtained by a titration method and the phase diagrams were calculated based on the Flory–Huggins thermodynamics. The DMF–SPU interaction parameter, χ 23 was determined by the intrinsic viscosity measurement. The water–SPU interaction parameter, χ 13 was measured by an equilibrium swelling experiment. As the Hard Segment fraction in SPU increased, the values of χ 23 increased slightly and those of χ 13 decreased significantly. The amount of water to achieve liquid demixing increased systematically with the Hard Segment Content. The χ 13 values in the practical concentration range were estimated by comparison of the calculated phase diagrams with the experimental cloud points. Liquid–liquid phase separation was coupled with liquid–solid phase separation (crystallization) when the SPU had high concentration of the Hard Segment. These coupled phenomena in combination with the phase segregation in SPU arising from the incompatibility between the Hard and soft Segments may be utilized to produce a variety of the morphologies of polyurethane membranes prepared by immersion precipitation.
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Liquid–liquid phase separation in a ternary system of Segmented polyetherurethane/dimethylformamide/water: effect of Hard Segment Content
Polymer, 2001Co-Authors: Hwan Kwang Lee, Jy Kim, Yd Kim, Jy Shin, Sung Chul KimAbstract:Abstract A series of Segmented polyurethanes (SPUs) using poly(tetramethylene oxide) (PTMO), 4,4′-methylenebis (phenyl isocyanate) (MDI), and ethylene glycol (EG) with different molar ratios of MDI and PTMO were prepared to study the effects of the Hard Segment Content in SPU on liquid–liquid phase separation in the SPU/dimethylformamide(DMF)/water system. The cloud points were obtained by a titration method and the phase diagrams were calculated based on the Flory–Huggins thermodynamics. The DMF–SPU interaction parameter, χ 23 was determined by the intrinsic viscosity measurement. The water–SPU interaction parameter, χ 13 was measured by an equilibrium swelling experiment. As the Hard Segment fraction in SPU increased, the values of χ 23 increased slightly and those of χ 13 decreased significantly. The amount of water to achieve liquid demixing increased systematically with the Hard Segment Content. The χ 13 values in the practical concentration range were estimated by comparison of the calculated phase diagrams with the experimental cloud points. Liquid–liquid phase separation was coupled with liquid–solid phase separation (crystallization) when the SPU had high concentration of the Hard Segment. These coupled phenomena in combination with the phase segregation in SPU arising from the incompatibility between the Hard and soft Segments may be utilized to produce a variety of the morphologies of polyurethane membranes prepared by immersion precipitation.
Yong-chan Chung - One of the best experts on this subject based on the ideXlab platform.
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Effect of glycerol cross-linking and Hard Segment Content on the shape memory property of polyurethane block copolymer
Journal of Materials Science, 2007Co-Authors: Byoung Chul Chun, Mi Hwa Chong, Yong-chan ChungAbstract:Effect of glycerol cross-linking and Hard Segment Content on the shape memory property of polyurethane block copolymer is comprehensively investigated. Phase separation of Hard and soft Segment is dependent on glycerol cross-linking and Hard Segment Content as judged from FT-IR and DSC data. Hydrogen bonding and dipole–dipole interaction between Hard Segments provides strong interaction between copolymer chains in addition to chemical cross-linking by glycerol. As the Hard Segment Content increases, the copolymer shows better tensile mechanical properties and higher melting temperature of soft Segment ( T _m). Effect of glycerol cross-linking on mechanical properties and T _m of soft Segment is low compared to Hard Segment effect. Although XRD peak at 2θ = 19.5° is observed, clear difference between the copolymers with various Hard Segment and cross-linking Content is not observed. Significant increase in shape recovery rate in the case of 30 wt% Hard Segment copolymer is observed after glycerol cross-linking. The drastic change of the properties of polyurethane block copolymer is discussed in the point of copolymer chain interaction.
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Enhanced mechanical and shape memory properties of polyurethane block copolymers chain-extended by ethylene diamine
European Polymer Journal, 2006Co-Authors: Byoung Chul Chun, Tae Keun Cho, Yong-chan ChungAbstract:Effect on shape memory and mechanical properties of polyurethane (PU) copolymers by changing the chain extender from 1,4-butanediol (BD) to ethylenediamine (ED) was investigated. PU copolymers composed of the different ratio of Hard and soft Segment were prepared and characterized by IR, DSC, XRD, and UTM. Glass transition temperature of PU increased to room temperature range by adopting ED as a chain extender. The XRD peak pattern changed with Hard Segment Content. ED type PU achieved the high mechanical properties at lower Hard Segment Content than BD type PU. Especially, strain at break of ED type significantly improved compared to BD type. Shape recovery rates were similar for both types of PU, but ED type showed better shape retention rate than BD type. The reason for the differences between two types of PU is discussed in this paper.
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Water vapor permeability and mechanical properties of fabrics coated with shape‐memory polyurethane
Journal of Applied Polymer Science, 2004Co-Authors: Jae Whan Cho, Byoung Chul Chun, Yong Chae Jung, Yong-chan ChungAbstract:Water vapor permeable fabrics were prepared by coating shape-memory polyurethane (PU), which was synthesized from poly(tetramethylene glycol), 4,4'-methylene bis(phenylisocyanate), and 1,4-butanediol, onto polyester woven fabrics. Water vapor permeability and mechanical properties were investigated as a function of PU Hard-Segment Content or polymer concentration of the coating solution. Water vapor permeability of PU-coated fabrics decreased dramatically with increased concentration of coating solution, whereas only a slight change was observed with the control of PU Hard-Segment Content. The coated fabric showed the clear appearance of a nonporous PU surface according to SEM measurements. Attainment of high water permeability in PU-coated fabrics is considered to arise from the smart permeability characteristics of PU. Mechanical properties of coated fabrics, although there was some variation depending on the concentration of coating solution, were primarily affected by PU Hard-Segment Content. Fabrics coated with PU Hard-Segment Content of 40% showed the lowest breaking stress and modulus as well as the highest breaking elongation, which could be interpreted in terms of the dependency of mechanical properties of coated fabrics on PU Hard-Segment Content and the yarn mobility arising from a difference in penetrating degree of coating solution into the fabric.
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Characterization and mechanical properties of prepolymer and polyurethane block copolymer with a shape memory effect
Fibers and Polymers, 2003Co-Authors: Jae Whan Cho, Byoung Chul Chun, Yong Chae Jung, Sun Hwa Lee, Yong-chan ChungAbstract:The prepolymer and the final polyurethane (PU) block copolymer were synthesized by reacting 4,4-methylene bis(phenylisocyanate) with poly(tetramethylene glycol) and the prepolymer with 1,4-butanediol as a chain extender, respectively, to investigate the relation between phase separation and it’s resulting properties. According to FT-IR data, the phase separation of Hard and soft Segments in the prepolymer and the PU block copolymer grew bigger by increasing the Hard Segment Content, and the PU showed more dominant phase separation than the prepolymer. The heat of fusion due to soft Segments decreased in both the prepolymer and the PU by increasing the Hard Segment Content, whereas the heat of fusion due to Hard Segments increased in the PU did not appear in the prepolymers. The breaking stress and modulus of the prepolymer increased by increasing the Hard Segment Content, and the elongation at break decreased gradually, and the PU showed the highest breaking stress and modulus at 58 % Hard Segment Content. However, the best shape recovery of the PU was obtained at 47 % Hard Segment Content due to the existence of proper interaction among the Hard Segments for shape memory effect. Consequently, the mechanical properties and shape memory effect of the PU were influenced by the degree of phase separation, depending on the incorporation of chain extender as well as the Hard Segment Content.
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structure and thermomechanical properties of polyurethane block copolymers with shape memory effect
Macromolecules, 2001Co-Authors: Bo Sun Lee, Byoung Chul Chun, Yong-chan Chung, And Kyung Il Sul, Jae Whan ChoAbstract:Shape memory polyurethane (PU) block copolymers composed of 4,4‘-methylenebis(phenylisocyanate), poly(tetramethylene glycol), and 1,4-butanediol as a chain extender were synthesized by a two-step process. FT-IR spectra showed that carbonyl peak appearing at 1700 cm-1 increased with higher Hard Segment Content, whereas another carbonyl peak at 1730 cm-1 decreased. It suggests that Hard Segments get more aggregated to form domains in the PU block copolymer as Hard Segment Content increases. Such domain formation has a significant influence on the mechanical and thermomechanical properties of PU, such as maximum stress, tensile modulus, and elongation at break. Especially, maximum stress, tensile modulus, and elongation at break increased significantly at 30 wt % of Hard Segment Content, and the highest loss tangent was observed at the same composition. Heat of crystallization as measured by differential scanning calorimetry is also dependent on the Hard Segment Content. Finally, 80−95% of shape recovery was...
Zhaosheng Hou - One of the best experts on this subject based on the ideXlab platform.
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Synthesis and properties of biodegradable poly(ester-urethane)s based on poly(ε-caprolactone) and aliphatic diurethane diisocyanate for long-term implant application: effect of uniform-size Hard Segment Content.
Journal of Biomaterials Science Polymer Edition, 2019Co-Authors: Li Zhang, Chunxia Zhang, Wenwen Zhang, Honghong Zhang, Zhaosheng HouAbstract:AbstractIn this article, a series of medical poly(ester-urethane)s (PEUs) with varying uniform-size Hard Segment Content were prepared via one-step chain extension of poly(e-caprolactone)s with ali...
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synthesis and properties of biodegradable poly ester urethane s based on poly e caprolactone and aliphatic diurethane diisocyanate for long term implant application effect of uniform size Hard Segment Content
Journal of Biomaterials Science-polymer Edition, 2019Co-Authors: Li Zhang, Chunxia Zhang, Wenwen Zhang, Honghong Zhang, Zhaosheng HouAbstract:AbstractIn this article, a series of medical poly(ester-urethane)s (PEUs) with varying uniform-size Hard Segment Content were prepared via one-step chain extension of poly(e-caprolactone)s with ali...
