• Elastomers and Composites
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• v.33 no.2
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• pp.93-102
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• 1998

In electric cable industries, the curing extent of the rubber materials covering the electric cores gives an significant effect on their final performance. The curing extent of rubber is controlled mostly by pull-out velocity of cable in the extrusion process. The final curing extent may be different for different radial positions inside the rubber because of the non-uniform temperature distributions during the curing process. In this contribution, the prediction of curing extent distribution throughout the radial direction of rubber is represented when the cable is passing through the steam curing zone with a fixed pull-out velocity. The prediction of the optimum pull-out velocity for the desired curing extent distribution is also reported. The steady-state heat balance was developed for the curing and cooling processes in which the pull-out rubber was cured by high temperature steam and then cooled by ambient water. A few essential material properties such as density, specific heat, and thermal conductivity were measured to analyze the temperature distribution during the curing and cooling processes. The times to reach 90% curing extent at varying temperatures were measured and used to determine the final cure extent distribution inside the rubber.

• Journal of the Korean Wood Science and Technology
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• v.36 no.6
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• pp.121-129
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• 2008

Environmental friendly UV-curable coatings, having excellent hardness, gloss, mar and chemical resistance, are commonly used for the wooden flooring coatings. Especially epoxy acrylate oligomers are chosen for the wooden flooring coatings, due to their thermal stability and fast curing. In this study, we investigated the effect of the acrylate functionality on the thermal stability and surface hardness. The thermal degradations of monomers, oligomer, photoinitiator and formulated coatings with different acrylate functionality were measured using a thermogravimetric analysis (TGA). And the surface hardness was also measured with a pendulum hardness tester to compare relationship between the thermal stability and the physical property. The cured coatings became thermally stable by crosslinking during UV-curing. Both the thermal stability and surface hardness of cured coatings were improved with increasing acrylate functionality.

• Polymer(Korea)
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• v.25 no.2
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• pp.168-176
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• 2001

The effect of novel N-crotyl-N,N-dimethyl-4-methylanilinium hexafluoroantimonate (CMH) curing agent as a thermal latent initiator on thermal behaviors, rheological properties, and thermal stability of diglycidylether of bisphenol A (DGEBA) epoxy cationic system was investigated. From DSC measurements of DGEBA/CMH system, it was shown that this system exhibits an excellent thermal latent characteristic at a given temperature. The conversion and conversion rate of DGEBA/CMH system increased with increasing the concentration of initiator, due to high activity of CMH. Rheological properties of the system were investigated under isothermal condition using a rheometer The gelation time was obtained from the analysis of storage modulus (G'), loss modulus (G"), and damping factor (tan $\delta$). As a result, the reduction of gelation time was affected by high curing temperature and concentration of CMH, resulting in high degree of network formation in cationic polymerization, due to difference of activity. The thermal stability of the cured epoxy resin was discussed in terms of the activation energy for decomposition and thermal factors determined from TGA measurements.ents.

• Restorative Dentistry and Endodontics
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• v.25 no.1
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• pp.91-108
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• 2000

Most of cervical abrasion and erosion lesions show gingival margin where the cavosurface angle is on cementum or dentin. Composite resin restoration of cervical lesion shrink toward enamel margin due to polymerization contraction. This shrinkage has clinical problem such as microleakage and secondary caries. Several methods to diminish contraction stress of composite resin restoration, such as modifying cavity form and building up restorations in several increments have been attempted. The purpose of this study was to compare polymerization contraction stress of composite resin in Class V cavity subjected to cavity forms and placement methods. In this study, finite element model of 5 types of Class V cavity was developed on computer tomogram of maxillary central incisor. The types are : 1) Box cavity 2) Box cavity with incisal bevel 3) V shape cavity 4) V shape cavity with incisal bevel 5) Saucer shape cavity. The placement methods are 1) Incisal first oblique incremental curing 2) Bulk curing. An FEM based program for light activated polymerization is not available. For simulation of curing dynamics, time dependent transient thermal conduction analysis was conducted on each cavity and each placement method. For simulation of polymerization shrinkage, thermal stress analysis was performed with each cavity and each placement method. The time-temperature dependent volume shrinkage rate, elastic modulus, and Poisson's ratio were determined in thermal conduction data. The results were as follows : 1. With all five Class V cavifies, the highest Von Mises stress at the composite-tooth interface occurred at gingival margin. 2. With box cavity, V shape cavity and saucer cavity, Von Mises stress at gingival margin of V shape cavity was lower than the others. And that of box cavity was lower than that of saucer cavity. 3. Preparing bevel at incisal cavosurface margin decreased the rate of stress development in early polymerization stage. 4. Preparing bevel at incisal cavosurface margin of V shape cavity increased the Von Mises stress at gingival margin, but decreased at incisal margin. 5. At incisal margin, stress development by bulk curing method was rapid at early stage. Stress development by first increment of incremental curing method was also rapid but lower than that by bulk curing method, however after second increment curing final stress was the same for two placement methods. 6. At gingival margin, stress development by incremental curing method was suddenly rapid at early stage of second increment curing, but final stress was the same for two placement methods.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.136-139
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• 2004

The domestic concrete standard specification(l999) reports roughly about heat transfer analysis and thermal stress analysis for mass concrete. Engineers cannot but choice after all numerical method such FEM, FDM to escape review. It seems to us that the specification is room for reconsideration because above methods are vary expensive and without popularity. This study suggests thermal distributed function in mass concrete. The function consists of two independent variables, curing time and depth. It's results have been tested a sensitivity for unit cement content, form condition, curing condition, and shape(depth, width). Results of the function are made a comparison with analytical values of MIDAS/CIVIL and a few measurement values. The researchers could meet with coherent and good results for variable cases.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1847-1850
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• 2008

The process conditions during ultraviolet nanoimprint lithography (UV-NIL) process such as temperature, stamping pressure, UV irradiation, etc. are effective factors for successful imprinting of complex and fine patterns. In this study, the effects of aluminum mold on the thermal characteristics of UV-NIL process were investigated through imprinting experiments and numerical simulations. The temperature of polymer resin on mold was measured to study thermal characteristics during UV curing. From the experimental and numerical results, the importance of curing reaction control for UV-NIL process was discussed for deformation characteristics.

• Textile Coloration and Finishing
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• v.20 no.4
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• pp.8-14
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• 2008

Flame-retardant cotton fabrics were prepared by UV curing of photocurable aqueous formulations of phosphorous-containing methacrylate monomers and 2-hydroxy-2-methyl-1-phenyl-1-propanone as flame retardants and a photoinitiator respectively, which is an environmentally friendly and energy-saving process. The characterization of the UV-coated cotton fabric was made by ATR, TGA and limited oxygen index measurement. UV cured coating onto cotton fabrics reduced the first thermal decomposition temperature and mass loss as well as increase in the amount of char residue compared with the untreated cotton fabric presumably due to modified thermal decomposition process. The LOI values up to 28.5 and 27.2 were obtained by the UV curing of MMEP and TMEP respectively. The treatment was durable to five laundering cycles, which was more prominent in the case of trifunctional TMEP treatment.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.548-551
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• 1999

The cure characteristics of metal particle filled DGEBA/MDA/SN/ zeolite epoxy resin composite system for EMI shielding were investigated by dynamic DSC run method and FT-lR spectroscopy. As the heating rate increased, the peak temperature on dynamic DSC curve increased because of the rapid cure reaction. From the straight line of the Kissinger plot, the curing reaction activation energy and pre-exponential factor could be obtained. As the post-curing time at 15$0^{\circ}C$ increased, the glass increased the glass transition temperature or the thermal stability increased. When the post curing time is too long, the system filled with metallic Al particle can be thermally oxidized by the catalytic reaction of metal filler and the thermal stability of the composite for the EMI shielding application may be decreased.

• Journal of the Korea Concrete Institute
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• v.25 no.2
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• pp.195-200
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• 2013

New thermal crack control system for mass concrete was developed to increase quality and to save construction period and cost. The principle of this system is that the curing water having proper temperature is supplied automatically to the surface of mass concrete member to keep the temperature difference between center and surface of concrete less than generally recommended temperature difference ($20^{\circ}C$). Mock-up test was conducted to investigate the validity of newly developed curing system. As a result, no crack was founded in the specimen using automated curing system developed in this study, while many cracks occurred in another specimen without automated curing system. It was also confirmed that the strength and the durability of the concrete cured by automated curing system were improved.

• Composites Research
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• v.34 no.3
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• pp.180-185
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• 2021

Due to the formation of random three dimensional network structure, which cause a lot of scattering of phonons, the thermal conductivity is low when the liquid crystalline epoxy is cured with amine-based curing agent. This problem is solved by using a cationic initiator that can make mesogen groups to be stacked structure. In this experiment, the thermal stability is compared by investigating the activation energy of isothermal decomposition through TGA of an epoxy using an amine-based curing agent and a cationic initiator. As a result, the energy of the activation of the epoxy using a cationic initiator is high. Compared with the previous experiments, the thermal stability is similar to the thermal conductivity.