• Journal of Adhesion and Interface
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• v.7 no.4
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• pp.45-52
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• 2006

Five low molar ratio urea-formaldehyde (LUF) resins were synthesized in this study. The effects of molar ratio, free formaldehyde content, and catalysts on the curing characteristics of LUF resins were studied by measuring its free formaldehyde content, pH value change after catalysts added, curing rate, and pot life, observing its cured appearance, and analyzing its thermal behavior. The results indicate that: 1) The LUF resin with lower molar ratio than 1.0 can still cure; 2) Free formaldehyde content is not the main factor in affecting curing rate of LUF resin; 3) Compared with ammonium chloride as a traditional catalyst, persulfate salts markedly accelerate the curing rate of LUF resin, and result in the different appearance; 4) the addition of sodium chloride to catalysts can accelerate the curing rate of LUF resin, but the effect is moderate.

• Journal of the Korean Applied Science and Technology
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• v.18 no.1
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• pp.40-48
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• 2001

Curing reaction was carried out with the acrylic resin (ACR) [n-butyl acrylate/atyrene/2-hydroxyethyl methacrylate/acetoacetoxyethyl methacrylate (AAEM)] synthesized before and a curing agent, hexamethoxymethylmelamine (HMMM). With rotational rheometer, the effect of catalysts on curing rate of acrylic resin/melamine was examined. Among the four catalysts used, p-toluene sulfonic acid showed the highest reactivity, and the optimum amount of catalyst was 0.5 phr. It was observed that in the ACR/HMMM curing reaction, gelation point was lowered with the increasing the amount of AAEM and HMMM in the ACR.

• Journal of Adhesion and Interface
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• v.2 no.3
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• pp.16-24
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• 2001

The curing behavior of a phenolic resin (F/p: 1.3, 1.9, 2.5 for resol resin, F/P: 0.5, 0.7, 0.9 for novolac resin) has been studied by FT-IR spectroscopy. In this study is to synthesis of resol and novolac type phenolic resin with different F/P molar ratios and to compare the level of cure at different curing temperature conditions ($130^{\circ}C$, $160^{\circ}C$, $180^{\circ}C$ for resol resin, $160^{\circ}C$, $170^{\circ}C$, $180^{\circ}C$ for novolac resin) for 3, 5, 7, 10, 20, and 60 (min.), respectively. The conversion (${\alpha}$) was determined by the ratio of the peak area with time to the peak area of non-baked phenolic QH ($3300cm^{-1}$) at spectra. It is concluded that the initial curing rate of resol and novolac resin was increased as the molar ratio of formaldehyde/phenol increased and as the curing temperature of resin increased. According to the analysis was by the homogenous first-order model, the initial curing rate of resol and novolac resin was increased as the molar ratio of formaIdehyde/phenol increased at specific curing temperature.

• Proceedings of the Materials Research Society of Korea Conference
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• 1994.11a
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• pp.125-126
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• 1994

The chemorheological changes and kinetics during curing reaction of an silica filled epoxy system (DGEBA with curing agent Polyxoypropylenediamine) were investigated. This study concentrates on the influence of silica on the reaction kinetics and rheological behavior of the eopxy system. The concentration of the filler was varied 0~200phr. Curing behavior of the silica filled epoxy system was measured at various heating rates with DSC. Conversion was also measured by integrating the obtained DSC curve and Kinetic parameters measured by using the nonlinear regression method. DSC experiments showed that the presence of silica was found to accelerate the progress of the curing reaction and of reduce the heat of reaction compared with that of unfilled epoxy systems . Rheological experiments were conducted on a Physica by using a disposable parallel plate fixture. Material properites were measured such as the elastic modulus(G′), the loss modulus(G"), the loss tangent(tan $\delta$), and the viscosity was at the initial stahe, and the more the silica filler was added, and the lower the gel temperature was in the epoxy system. In this study it is concluded that the curing of the silica filled epoxy system was found to be accelerated, as silica was added to the epoxy compound.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.738-741
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• 2001

We carried out aminolyses of various rigid polyurethane foams (PUFs) using diethylene triamine and studied application of the aminolysis products as hardners of epoxy resins. Diglycidyl ether of bisphenol A was used for the study on the curing behavior of epoxy resin with the aminolysis product employing differential scanning calorimeter. Curing reaction of the epoxy resin is generally known to be autocatalytic second order reaction. We found that the curing reaction of the epoxy resin with the aminolysis product of rigid PUF did not show autocatalytic characteristics but followed the n-th order kinetics. The activation energy of the curing reaction of the epoxy resin with the aminolysis product of rigid PUF made from sugar based polyol was slightly lower than that of the epoxy resin with aminolysis product of rigid with made from amine based polyol.

• Advances in concrete construction
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• v.11 no.4
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• pp.347-356
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• 2021

To address the limitation of the commonly used steam curing of reactive powder concrete (SC-RPC) in engineering, a preparation technology of normal curing reactive powder concrete (NC-RPC) is proposed. In this study, an experimental comparative research on the mechanical properties of NC-RPC and SC-RPC under uniaxial tension is conducted. Under the premise of giving full play to the ultra-high performance of RPC, the paper tries to explore whether normal curing can replace steam curing. The results show that various mechanical indexes of NC-RPC (e.g., tensile strength, ultimate tensile strain, elastic modulus and deformation performance) could basically reach the mechanical index values in steam curing at 28d age, some performance is even better at a longer age. So it affirms the feasibility of normal curing. In this paper, the influence of normal curing age on the tensile properties of RPC is discussed, and the relationship between each index and age is introduced in detail. Based on the experimental data, the tensile mechanism of RPC is analyzed theoretically, and two kinds of tensile constitutive models for RPC are proposed, one is curvilinear model, and another one is polygonal line model. The validity of the two models is further verified by the test results of others.

• Journal of Adhesion and Interface
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• v.12 no.1
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• pp.34-42
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• 2011

The roll coating process is well-known for completely replacement coating system with an existing wet paint process for automotive which has low productivity and is not environment-friendly process. It is very important to evaluate the curing behavior, corrosion resistance and processing property as well as rheological behavior in order to realize a film flexibility and hardness simultaneously. In this study, we have synthesized the polyester resin modified with hydroxyl values and molecular weight to apply the pre-painted system, and then evaluated the curing behavior, deep drawing, tensile strength and rheological properties. It was observed that N-0375-40 of 40 (mg KOH/mol) hydroxyl values showed the most suitable for flexibility, film hardness, and curing behavior.

• Polymer(Korea)
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• v.39 no.2
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• pp.256-260
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• 2015

The addition of montmorillonite (MMT) in the UV curable polyurethane diacrylate based resins was investigated to fabricate nanocomposites with improved mechanical properties and water sorption behavior using different photoinitiator systems. As a result, it was observed that 1 wt% of clay loading fairly improved tensile resistance and water uptake behavior. It can be also confirmed that dual photoinitiator system consisted of benzyldimethyl ketal and bisacyl phosphine oxide exhibited enhanced energy absorption band 340~450 nm even with 3 wt% of MMT concentration, which may affect the curing behavior of nanocomposite especially in our UV lamp system.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.1013-1016
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• 2003

This paper is to evaluate practically the techniques and materials of repair for RC elements with fire damages as well as to investigate the structural behavior of RC beams according to pre- or post-repair after fire-damages. For this purpose, normal concrete flexural specimens were exposed to high temperatures by the ISO 834 specification. After natural cooling and post-fire-curing in a natural environment for 2 months, the specimens were repaired with polymer cement mortar for 1 month curing.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.481-484
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• 2004

This study was performed to analyze effect of cyclic load during CFS curing on the behavior of RC beam strengthened with CFS. In the experiment, five different beginning times of cyclic load and two different strengthening amounts of CFS were chosen for experiment parameters. From the experimental results, it could be known that the cyclic load during CFS curing might give detrimental effects to the CFS strengthening effects compared to without cyclic load cases.