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Discoloration mechanism of UV-curable polymer/metal hybrid coating
김문호,최길영,이종배 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.1
The purpose of this study is to conduct an in-depth analysis of the discoloration mechanism of UVcurable polymer/metal hybrid coating. A variety of technical approaches, including microscopic,spectroscopic, and chromatographic analysis techniques, were used to investigate the nature of discoloration and the root cause. The hybrid coating has a typical multilayered structure consisting of a base coat, a vacuum deposited metal layer, and a top coat. The results obtained by microscopic and spectroscopic analyses demonstrated that the discoloration of the hybrid coating stemmed from yellowing of the top coat. Deterioration or degradation of the metal component in the vacuum deposited metal layer was not confirmed. The results of an analysis of additives in the discolored top coat showed that there is a small quantity of unreacted photoinitiators remaining in the top coat. From the results of solvent extraction and gel content measurement, it is believed that an excessive amount of photoinitiators was used in the resin of the top coat and one of the residual unreacted photoinitiators caused yellowing of the top coat.
Discoloration mechanism of polymer surface in contact with air–water interface
김문호,최길영,변두진,유지은 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.3
The white-colored inner surface of a polypropylene (PP) material containing water discolored and turned yellow. The discoloration occurred selectively on the surface at the point of contact with the air–water interface. Since the polymer surface was exposed to water in darkness at room temperature, no sign of deterioration or degradation of the polymer at the discolored surface was confirmed. This study conducts an in-depth analysis of the discoloration mechanism of the polymer surface. A variety of technical approaches, including microscopic, spectroscopic, and chromatographic analysis techniques, were used to investigate the nature of discoloration and the root cause. From the analysis results, the discoloration was ascribed principally to a phenol transformation compound having the structure of a quinone methide, which was identified as a degradation product of a primary antioxidant. Based on the observations and experimental results, a plausible discoloration mechanism was proposed.
7050 Al합금의 가공열처리가 미세조직변화와 피로성질에 미치는 영향
김문호,권숙인 ( M . H . Kim,S . I . Kwun ) 한국열처리공학회 1991 熱處理工學會誌 Vol.4 No.4
The effects of thermomechanical treatments on microstructure and fatigue properties of 7050 Al alloy were investigated. The precipitation kinetics changed to a faster rate due to cold deformation employed in this special TAHA thermomechanical treatments including pre-aging, plastic deformation and two step final-aging. The G.P. zones in the under-aged condition were cut by dislocations and dissolved during the plastic deformation. During the low cycle fatigue, the T6` condition showed cyclic hardening behavior whereas the TMT5, TMT27 and T76 conditions showed cyclic softening at above 0.7% total strain amplitudes. The ΔK_(th) value of TMT27 was improved more than two times, compared with that of T76 condition. The T6` with small shearable precipitates resulted in the markedly high ΔK_(th) value. This is thought to be resulted from dislocation reversibility and roughness-induced crack closure due to planarity of slip.
Deformation Behavior of Polymeric Colloidal Photonic Crystals Induced by UV Irradiation
김문호,변두진,송시용,신세문,곽수경,최길영 한국고분자학회 2013 Macromolecular Research Vol.21 No.12
The deformation behavior of polymeric colloidal photonic crystals (CPCs) during UV irradiation was investigated. A CPC grown from a polystyrene (PS) colloidal suspension was prepared and exposed to UV light. The UV irradiation resulted in photochemical reactions that induced morphological changes in the surfaces of CPC,including deformations in the sizes, shapes, and packing structures of the PS particles. The crystal morphology evolution resulting from UV irradiation differed significantly from the photoaging behavior observed during exposure to a light source that mimicked natural sunlight. The structural deformations destroyed the optical properties (by deteriorating the photonic bandgap). The UV irradiation induced photooxidation processes that altered the composition of the polymer material surface.
사과나무 腐爛病에 關한 硏究(Ⅰ) : Valsa ceratosperma의 代謝生成物質에 對하여 on the metabolite of Valsa ceratosperma
金文鎬,李準琸 慶北大學校 1975 論文集 Vol.20 No.-
In this study a phytotoxic metabolite extracted from the culture filtrate of Valsa ceratosperma causing apple canker, and some experiment was carried out on the effect of this metabolite to the apple tree and the growth of the fungus. The results obtained are as follows. 1. The metabolite has an inhibitory effect upon the growth of V. ceratosperma and the inhibitory effect seemed to be lost when the metabolite absorbed into apple tree tissue. 2. With the treatment of high concentration on artificial wound, metabolite caused necrosis on apple tree tissue. 3. Apple tree cuttings absorbed with metabolite solution of high cocentration showed a decrease of resistant activity against the invasion of fungus, and vice versa. 4. The treatment of apple tree cuttings with metabolite solution of high cocentration caused wilting on the leaf and discoloration of phloem and surface of xylem. These aspect of injuries was similar with that of a twig infected with apple canker. Some differences of injurious effect of this metabolite were observed between the varieties of apple tree.