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정용찬,박언호,최재원,전병철 대한화학회 2017 Bulletin of the Korean Chemical Society Vol.38 No.10
The graft polymerization of tert-butyl acrylate (TBA) onto polyurethane (PU) was conducted to prepare a series of samples that was compared to a control series comprising a physical mixture of poly(TBA) and PU. Maximum tensile stress sharply increased because of chemical cross-linking via poly(TBA), whereas tensile breaking strain slightly diminished by the grafted poly(TBA). Percent shape recovery at 10°C rapidly increased by the additional grafting of poly(TBA), whereas control series decreased with increases in TBA monomer content. Chemical cross-linking from the grafted poly(TBA) was responsible for the enhancement of shape recovery. Low-temperature flexibility tests from −35°C demonstrated that a proper composition of grafted poly(TBA) could enhance the flexibility of PU below 0°C. Overall, the grafted poly(TBA) greatly stepped up the maximum tensile stress, recovery capability to original form, and flexibility of PU at very low temperature.
정용찬,박지은,최재원,전병철 대한화학회 2019 Bulletin of the Korean Chemical Society Vol.40 No.4
Noticeable enhancements in the (a) breaking tensile stress and (b) shape recovery rate after the grafting of polystyrene onto PU in PS series.
정용찬,구교진,현창택 대한건축학회 2004 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.24 No.1
Recently, as the building height goes up, the construction period of finishing materials has become one of the most important key issues in the tall building construction. For the reason, one of the vertical transportation equipment, the lift car is more important than before. So. this study reviews properties and problems of the lift car planning in the tall building construction field, and systemizes the process of how many lift cars are suitable in the field. Also, this study suggests the lift car selecting model to calculate exact figures of finishing materials and workers.
정용찬,김동의,최재원,전병철 한국고분자학회 2020 Macromolecular Research Vol.28 No.2
Perpendicular cardo structural units were inserted into a polyurethane (PU) framework from the pH indicator (phenolphthalein (PP), phenol red (PR), or bromocresol green (BG)) sharing a triphenylmethyl group. The thermal transitions, mechanical properties, pH-sensitive color change, and low temperature flexibility of the PU modified with the cardo structural units were compared with those of the ordinary PU. Slight cross-linking between PU chains was performed because the insertion of the indicator moieties deteriorated the mechanical properties. The breaking tensile stress and shape recovery capability at 0 °C of the BG-PU series surpassed those of the PP-PU and PR-PU series. The inserted pH indicator moieties did not show the color change under different pH conditions because the isomerization under basic conditions was blocked. Among the three series of PUs, the BG-PU demonstrated the best low temperature flexibility compared with that of the PP-PU and PR-PU due to the functional groups on the phenyl rings of BG. Insertion of a cardo structural unit from the pH indicator reduced the molecular interaction between PU chains.
정용찬,박지은,최재원,전병철 한국고분자학회 2021 Macromolecular Research Vol.29 No.11
Melamine was grafted to a polyurethane (PU) frame and utilized for crosslinking PU via amino groups. The degree of crosslinking and the solution viscosity increased notably after grafting melamine due to the formation of crosslinks. The thermal transition of the soft segment was not significantly affected, but the glass transition was observed at a slightly higher temperature in case of the grafted melamine. Melamine-mediated crosslinking increased not only the breaking tensile stress but also the shape recovery performance of PU. In addition, crosslinked PU was more flexible at low temperature than unmodified PU. Overall, melamine-mediated crosslinking improved the tensile resistance to stress, the recovery tendency to the initial shape, and the flexibility with minor changes in the thermal transition, tensile strain, and shape retention at a low temperature.
정용찬,전병철,박종신,신창훈,최재원 한국고분자학회 2012 Macromolecular Research Vol.20 No.1
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.