• Polymer(Korea)
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• v.24 no.3
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• pp.350-357
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• 2000

Curing behaviors of glass/epoxy prepreg for printed circuit boards (PCB) were studied by using dielectrometer and differential scanning calorimeter. This prepreg was showed the lowest ionic viscosity at about 115$^{\circ}C$, and then the ionic viscosity was gradully increased up to 15$0^{\circ}C$. This indicated that the curing reaction of this prepreg started at 115$^{\circ}C$ and the molecular weight was increased by the accelerated thermal cross-linking reaction. The loss factor and tan $\delta$ values were also measured and discussed. The dielectric behaviors of this prepreg system were also measured according to the cure cycle for PCB. This material was found to be thermally stable up to about 30$0^{\circ}C$ and then was showed an abrupt decomposition beyond this temperature.

• Polymer(Korea)
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• v.37 no.5
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• pp.557-562
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• 2013

The thermal expansion and mechanical properties of diglycidyl ether of bisphenol A (DGEBA) with mercaptan hardeners were studied by a comparative method with an amine-adduct type hardener. Thermal expansion and dynamic mechanical properties were measured by thermo mechanical analysis (TMA) and dynamic mechanical ananlysis (DMA), respectively. The $T_g$ and the coefficient of thermal expansion (CTE) of epoxy/amine-adduct type hardener system were $82.6^{\circ}C$ and 71.2 $ppm/^{\circ}C$, respectively. As the number of -SH functional group of mercaptan hardener increased, the $T_g$ rapidly decreased and gradually increased up to ca. $80^{\circ}C$ and the CTE under the $T_g$ rapidly increased to ca. 200 $ppm/^{\circ}C$ from 80 $ppm/^{\circ}C$ and decreased to ca. 100 $ppm/^{\circ}C$. The crosslinking density of epoxy with amine-adduct type hardener was ca.1.5 $mol/cm^3$, while that of epoxy with mercaptan hardeners increased from 1.0 to 1.7 $mol/cm^3$, as the number of -SH functional group increased. The storage modulus can increase up to 2700MPa at $30^{\circ}C$.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.612-615
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• 2003

Maskless laser patterning process is developed using 3rd harmonic Diode Pumped Solid State Laser with near visible wavelength of 355 nm. Photo-sensitive curable polymer is irradiated by UV laser and developed using polymer solvent to obtain quasi-3D patterns. We performed basic experiments for the various process conditions such as laser power, writing speed, laser focus, and polymer optical property to gain the optimal conditions. Experimentally, the patterns of trapezoidal shape were manufactured into dimension of 8${\mu}{\textrm}{m}$ width and 5.4${\mu}{\textrm}{m}$ height. This process could be applied to fabricate a single mode waveguide without expensive mask projection method.

• Magazine of the Korean Society of Agricultural Engineers
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• v.43 no.4
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• pp.106-112
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• 2001

Recent advance in material technology has accelerated the development of high strength concrete using lightweight artificial aggregates. The lightweight concrete has many advantages that the reduction of dead loads and the increase in load capacity can offer. In this study the lightweight polymer concrete using unsaturated polyester resin and lightweight aggregate were prepared and tested for testing the physical and the mechanical properties. The compressive strengths of lightweight polymer concretes with apparent specific gravity for 1.32 to 1.78 were 250 to 470 kfg/cm$^2$ and flexural strengths were measured to be in the range of 1/3-1/4 of compressive strength.

• Journal of the Korea Concrete Institute
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• v.18 no.2 s.92
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• pp.227-232
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• 2006

This article presents the results of experimental study that investigates the effect of filler and shrinkage reducing agent influencing on the strength properties of MMA-modified polymer paste that was produced to develop the surface-repair and coating materials of the concrete structures. Results show that the flexural and compressive strengths of the polymer paste increased 29 and 27%, respectively, when the aluminum hydroxide completely replaced the calcium carbonate as the filler Furthermore, when the shrinkage reducing agent was used 30%, both strengths decreased about 29% comparing to when the agent was not used. As in the cases of flexural and compressive strengths, the adhesive strength increased as the content of aluminum hydroxide as the filler increased, and it decreased as the content of shrinkage reducing agent increased. The adhesive strength with a dry concrete substrate turned out to be $30{\sim}40%$ higher than that with a wet concrete substrate.

• Journal of the Korea Concrete Institute
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• v.23 no.1
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• pp.121-127
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• 2011

In this study, possible use of indigenous natural loess (Hwangtoh) as a new binding material via geopolymerization process is examined. Hwangtoh pastes with four different mix proportions of varying alkali liquid concentrations (6 M, 8 M) and the constituents of the binder as well as the alkali liquid at a constant liquid-to-binder ratio of 0.55 were prepared. Analysis of the natural loess (Hwangtoh) paste was carried out as follows : 1) Measurement of compressive strength and weight of cubic specimens versus curing time; 2) Analysis by X-ray diffraction (XRD) and scanning electron microscope (SEM) about reaction product; 3) Porosity analysis of hardened Hwangtoh paste. The result showed that it is possible to prepare Hwangtoh paste with 29.1 MPa at the age of 7 day by using alkali solution (made as 1 : 4.5 the mass ratio of liquefied $Na_2SiO_3$ and NaOH solution and applying the curing temperature of $60^{\circ}C$). Compressive strength development with respect to the degree of moisture evaporation from the paste seems to be independent of curing temperature. Therefore, it seems that higher early strength of the paste specimens cured at higher temperature can be attributed to both higher rate of reaction and moisture evaporation.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.9 no.2
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• pp.81-86
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• 2011

Polymer-modified cement is the composite material made by partially replacing and strengthening the cement hydrate binders of conventional mortar with polymeric modifiers such as polymer latexes and redispersible polymeric modifiers. It is known that the addition of polymer to cement mortar leads to improved quality, which would be expected to have a high chemical resistance. Therefore, the purpose of this study is to identify the improved chemical resistance, such as low permeability and low ion diffusivity, of the polymer-modified cement as a solidification agent for the radwaste. First, polymer-modified cement specimens by latex modification were prepared according to the polymer content from 0% to 30% to select the optimized polymer content. At those specimens, the water-to-cement (W/C) ratio was maintained to 33% and 50% respectively. After the much curing time, the structural integrity of specimens was evaluated through the compressive strength test and the porosity evaluation by the water immersion method. From the results, 10% of the polymer content at 33% of the W/C ratio was shown to have the most improved quality. Finally, the leaching test referredfrom ANS 16.1 for the specimens having the most improved quality was conducted. Dedicated specimens for the leaching test were then mixed with radioisotopes of $^{60}Co$ and $^{137}Cs$ at the specimen preparation.

• Polymer(Korea)
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• v.34 no.3
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• pp.191-197
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• 2010

To improve the curing method of anisotropic conductive film (ACF) at low temperature, it was studied to replace the thermal latent curing agent of imidazole compounds by the curing agent of cationically initiating type. Thermo-mechanical properties such as glass transition temperature, storage modulus, and coefficient of thermal expansion were investigated for the analysis of curing behavior. The reliability of ACF were observed in thermal cycle and high temperature-high humidity test. ACF using cationic initiator showed faster curing, lower CTE, and higher $T_g$ than the case of using imidazole curing agent, which is important for the high temperature stability. Furthermore, ACF using cationic initiator maintained a stable contact resistance in reliability test, although it was cured at low temperature and fast rate. With these results, it was confirmed that the curing method of epoxy had great effect on thermo-mechanical properties and reliability of ACF.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.21-22
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• 2014

The purpose of this study is to ascertain strengths and hardening rate of epoxy-modified mortar with wood-tar contents. The polymer-modified mortars (PMMs) using epoxy resin with wood-tar are prepared with various polymer-binder ratios of 1, 3, 5% and wood-tar contents of 0, 5, 10, 15 and 20%. The PMMs using epoxy resin are tested for compressive, flexural and tensile strengths and hardening rate of epoxy resin. As a result, the strengths and hardening rate under polymer-binder ratio 1% and wood-tar content of 5% are more excellent than those of other specimens.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.255-257
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• 2012

Epoxy resin without any hardener can harden in the presence of hydroxide ions in cement mortars and concretes at ambient temperature. The purpose of present study is to examine the hardening properties of hardener-free epoxy-modified mortars by curing conditions. The hardener-free epoxy-modified mortars using diglycidyl ether of A epoxy resin are prepared with various polymer-cement ratios, and subjected to initial moist/dry curing, initial steam(90℃) curing, initial steam/heat(80℃, 100℃) curing.As a result, degree of hardening of epoxy resin in initial moist/dry cured, initial steam cured and initial steam/heat(80℃) cured hardener-free epoxy-modified mortars is decreased with increasing polymer-cement ratio. However, it is markedly improved with additional dry-curing periods. On the other hand, regardless of the polymer-cement ratio and dry curing periods, degree of hardening of hardener-free epoxy-modified mortars with initial steam/heat(100℃) cure is over 95%.