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المؤلفون: Ji Eun Park, Byoung Chul Chun, Ji Young Kim, Yong-Chan Chung
المصدر: Fibers and Polymers. 22:904-915
مصطلحات موضوعية: Materials science, Polymers and Plastics, General Chemical Engineering, Ionic bonding, 02 engineering and technology, General Chemistry, 010402 general chemistry, 021001 nanoscience & nanotechnology, Grafting, 01 natural sciences, 0104 chemical sciences, law.invention, Contact angle, chemistry.chemical_compound, chemistry, Chemical engineering, law, medicine, Phenol, Fiber, Swelling, medicine.symptom, Crystallization, 0210 nano-technology, Polyurethane
الوصف: 2,4,6-Tris(dimethylaminomethyl) phenol (TDMP) was used as a grafted functional group to modify the hydrophilicity of polyurethane (PU) and to enhance the mechanical properties and low-temperature flexibility of PU. The grafted TDMP after conversion to the ionic form notably enhanced the hydrophilicity of PU, as confirmed by the water contact angle, water swelling, and water vapor permeability results. The light crosslinking that occurred during the grafting step increased the crosslink density and solution viscosity but did not disturb the solvation of PU. The melting of the soft segment was not affected by the grafted TDMP, but the crystallization of the soft segment was significantly reduced. The breaking tensile stress and shape recovery capability were notably enhanced, but the breaking tensile strain and shape retention capability were not impaired. In addition, the grafted TDMP notably improved the flexibility of PU at very low temperature compared with that of plain PU and control series PU. Overall, it is worth grafting TDMP onto PU considering the simple preparation method, the novelty of the modification mechanism, the notable enhancement in hydrophilicity, and the potential applications in fiber and biomedical fields.
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المؤلفون: Dong Eui Kim, Yong-Chan Chung, Jae Won Choi, Byoung Chul Chun
المصدر: Polymer-Plastics Technology and Materials. 58:656-666
مصطلحات موضوعية: Materials science, Polymers and Plastics, General Chemical Engineering, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, Grafting, 01 natural sciences, 0104 chemical sciences, law.invention, chemistry.chemical_compound, Membrane, chemistry, Polymerization, Chemical engineering, law, Ultimate tensile strength, Materials Chemistry, Poly(N-isopropylacrylamide), Crystallization, 0210 nano-technology, Glass transition, Polyurethane
الوصف: Poly(N-isopropylacrylamide) (poly(NIPAM)) was grafted onto polyurethane (PU) using a graft-polymerization method to develop a thermo-responsive PU and to investigate the impact on cross-link density, solution viscosity, soft segment thermal transitions, tensile properties, shape memory effect, and water vapor permeation through PU membrane. The soft segment crystallization peak sharply decreased with the increase in NIPAM content, whereas the glass transition temperature (Tg) slightly increased with the increase of NIPAM content. The breaking tensile stress rapidly increased with the increase in NIPAM content due to the cross-linking effect between the grafted poly(NIPAM) chains, whereas the strain at break did not significantly decreased as the NIPAM content increased. The shape recovery at 10°C rapidly increased from 46.9% for plain PU to above 90% after the grafting of poly(NIPAM) onto PU, and the shape retention at −25°C slightly decreased with the increase in NIPAM content. Finally, the graft...
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_________::13d2a2c9bf655d9c6cbee4c2ee06313d
https://doi.org/10.1080/03602559.2018.1520247 -
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المؤلفون: Byoung Chul Chun, Jae Won Choi, Gi Young Kim, Dong Eui Kim, Yong-Chan Chung
المصدر: Polymer Bulletin. 76:2041-2060
مصطلحات موضوعية: chemistry.chemical_classification, Polymers and Plastics, 02 engineering and technology, General Chemistry, 010402 general chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Grafting, 01 natural sciences, 0104 chemical sciences, law.invention, Salicylanilide, chemistry.chemical_compound, Polyol, chemistry, Chemical engineering, law, Barnacle (slang), Ultimate tensile strength, Materials Chemistry, Crystallization, 0210 nano-technology, Glass transition, Polyurethane
الوصف: Grafting of niclosamide or salicylanilide onto polyurethane (PU) was executed to develop antifungal effectiveness and barnacle repelling capability in seawater compared with underivatized PU. The PU surface was simultaneously modified to improve the surface hydrophilicity by inserting dimethylolpropionic acid into PU frame or by grafting recycled polyols onto PU. Surface modifications of PU significantly affected its properties, such as cross-link density, tensile and shape memory properties, and flexibility under freezing conditions relative to the unmodified PU. The modification of PU surface also notably influenced the glass transition and the melting and crystallization related to soft segments. The breaking tensile stress and the shape recovery were enhanced significantly after the grafting of polyol due to chemical cross-linking, whereas the breaking tensile strain was not reduced. Some PU samples demonstrated complete antifungal effectiveness against a mixture of fungi, and barnacle growth on PU films was limited in the specifically modified PUs.
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المؤلفون: Byoung Chul Chun, Yong-Chan Chung, Ho-Sung Kim
المصدر: Polymers and Polymer Composites. 26:141-153
مصطلحات موضوعية: Materials science, Polymers and Plastics, Graphene, Oxide, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, 01 natural sciences, 0104 chemical sciences, law.invention, chemistry.chemical_compound, chemistry, law, Ultimate tensile strength, Materials Chemistry, Ceramics and Composites, Polymer composites, Surface modification, Graphite, Composite material, 0210 nano-technology, Sheet resistance, Polyurethane
الوصف: Reduced graphene oxide (RGO) or graphite is functionalized with hydroxyl groups for linking to the sides of polyurethane (PU) chains. Blended PU with RGO or graphite is prepared as a control for comparison. The PU composites are compared with respect to their spectroscopic, thermal, mechanical, shape memory, and sheet resistance properties. Scanning electron microscopy images demonstrate the good distribution of functionalized graphene oxide (FGO) or functionalized graphite (FG) particles on the inner surface of the PU. The linking of FGO or FG onto PU does not significantly affect the thermal behavior or shape memory properties but sharply improves the tensile strength of the PU composites without a noticeable decrease in tensile strain. The shape recovery of PU composites remains at approximately 90%, regardless of the FGO or FG content. The FG-linked PU composites exhibit a sharp decrease in sheet resistance as the FG content increases, whereas the sheet resistance of the FGO-linked PU composites does not decrease with increasing FGO content. The control PU composites with blended RGO or graphite show significant reductions in their sheet resistance. Considering the ease of functionalization of the graphite surface and the significant improvement in tensile strength, linking FG onto PU is advantageous for the development of PU composites with low sheet resistance.
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المؤلفون: Jae Won Choi, Byoung Chul Chun, Yong-Chan Chung, Byung Hee Lee
المصدر: Advances in Polymer Technology. 37:323-331
مصطلحات موضوعية: Materials science, Polymers and Plastics, General Chemical Engineering, Organic Chemistry, 02 engineering and technology, 010402 general chemistry, 021001 nanoscience & nanotechnology, Elastomer, 01 natural sciences, 0104 chemical sciences, law.invention, chemistry.chemical_compound, chemistry, law, Thermal, Ultimate tensile strength, Water vapor permeability, Epichlorohydrin, Crystallization, Composite material, 0210 nano-technology, Glass transition, Polyurethane
الوصف: Epichlorohydrin (ECH) was used as a cross-linking agent for a series of polyurethanes (PU series). The spectroscopic, thermal, tensile, shape memory, low-temperature flexibility, and water vapor permeability properties of these PUs were compared with those of a control polyurethane series (CPU series) without ECH cross-linking. In the thermal test, the soft segment crystallization of the PU series disappeared as the ECH cross-linking increased. The glass transition temperature (Tg) of the PU and CPU series slightly increased with the increase in ECH content. The tensile strength of the PU series sharply increased at a critical ECH content, whereas that of the CPU series did not. The breaking strain of the PU and CPU series remained the same with the increase in ECH content. The shape recovery of the PU series remained above 90% at 45°C but increased moderately with the increase in ECH content at 0°C. Finally, the PU series with ECH cross-linking demonstrated better low-temperature flexibility and lower water vapor permeability than the unmodified PU.
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المؤلفون: Su Hyeon Jo, Byoung Chul Chun, Byoung Hee Lee, Yong-Chan Chung
المصدر: Polymer-Plastics Technology and Engineering. 54:1066-1076
مصطلحات موضوعية: Materials science, Polymers and Plastics, General Chemical Engineering, Materials Science (miscellaneous), Grafting, law.invention, chemistry.chemical_compound, chemistry, law, Ultimate tensile strength, Materials Chemistry, Side chain, Copolymer, Polystyrene, Crystallization, Composite material, Polyurethane
الوصف: A polyurethane series containing grafted polystyrene and a Control series with free polystyrene were prepared, and their spectroscopic, thermal, tensile, shape-memory, and low-temperature flexibility properties were compared. The grafted polystyrene significantly reduced the ΔHc and also reduced the crystallization peaks of the polyurethane series. The tensile strength of the polyurethane series sharply increased with polystyrene content, whereas the Control series did not. The shape recovery of the polyurethane series remained high but the shape retention gradually decreased after four repeated tests. Lastly, the polyurethane series grafted with polystyrene demonstrated excellent low-temperature flexibility.
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المؤلفون: Byoung Chul Chun, Jong Shin Park, Yong-Chan Chung, Chang Hoon Shin, Jae Won Choi
المصدر: Macromolecular Research. 20:66-75
مصطلحات موضوعية: Materials science, Aqueous solution, Polymers and Plastics, Electrolysis of water, General Chemical Engineering, Organic Chemistry, Electrolyte, Grafting, Polymer engineering, Cathode, law.invention, chemistry.chemical_compound, Chemical engineering, chemistry, law, Ultimate tensile strength, Polymer chemistry, Materials Chemistry, Polyurethane
الوصف: Shape memory polyurethane (SMPU) grafted using polyethyleneimine (PEI) was tested for its electrolytic attraction in aqueous solution and shape memory effect. The PEI was connected through a second 4,4′-diphenylmethane diisocyanate anchored to the carbamate moiety of SMPU. Two series of SMPU that differed in soft segment polytetramethylene glycol and PEI content were prepared to compare their tensile and shape memory properties. Shape recovery was high as 99% and reduced only to 97% after four test cycles. The PEI group attached to the SMPU chain, if converted to the imminium salt form, was designed to work as an electrolyte during water electrolysis and was to be attracted toward the cathode to show SMPU movement in aqueous solution. The electrolytic attraction of SMPU in aqueous solution was demonstrated in an experiment in which a specimen moved to the cathode only when voltage above a minimum was applied. The mechanism and application of this finding are discussed. Open image in new window
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المؤلفون: Woo Seok Kim, Yong-Chan Chung, Byoung Chul Chun, Tae Keun Cho
المصدر: Fibers and Polymers. 9:388-392
مصطلحات موضوعية: Materials science, Polymers and Plastics, General Chemical Engineering, Melting temperature, Enthalpy, Extender, General Chemistry, Dynamic mechanical analysis, Shape-memory alloy, law.invention, chemistry.chemical_compound, chemistry, law, Copolymer, Glycerol, Composite material, Polyurethane
الوصف: A series of shape memory polyurethane (PU) copolymers synthesized from 1,4-phenyldiisocyanate (PDI), poly(tetramethyleneglycol) (PTMG), 1,4-butanediol (BD) as a chain extender, and glycerol as a cross-linking agent were tested for the mechanical properties and the shape memory effect at the temperature 20 °C above melting temperature (Tm), and were compared with other PUs synthesized from 4,4′-methylene-bis-phenyldiisocyanate (MDI), PTMG, and BD. Mechanical properties and shape memory effect were improved substantially by adopting both PDI and glycerol. Interestingly, enthalpy of melting and Tm were not affected by the glycerol content. Vibration and shock absorption ability was investigated by measuring both loss tan δ and storage modulus with dynamic mechanical analyzer (DMA).
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المؤلفون: Byoung Chul Chun, Tae Keun Cho, Yong-Chan Chung
المصدر: European Polymer Journal. 42:3367-3373
مصطلحات موضوعية: Materials science, Polymers and Plastics, Hydrogen bond, Organic Chemistry, Extender, General Physics and Astronomy, Ethylenediamine, Shape-memory alloy, Atmospheric temperature range, law.invention, chemistry.chemical_compound, chemistry, law, Materials Chemistry, Copolymer, Composite material, Glass transition, Polyurethane
الوصف: 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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المؤلفون: Sun Hwa Lee, Yong Chae Jung, Byoung Chul Chun, Yong-Chan Chung, Jae Whan Cho
المصدر: Fibers and Polymers. 4:114-118
مصطلحات موضوعية: Materials science, Polymers and Plastics, General Chemical Engineering, Enthalpy of fusion, Extender, Modulus, General Chemistry, law.invention, chemistry.chemical_compound, chemistry, law, Copolymer, Elongation, Composite material, Phenylisocyanate, Prepolymer, Polyurethane
الوصف: 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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