• Korean Journal of Agricultural Science
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• v.32 no.1
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• pp.19-27
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• 2005

This study was performed to evaluate the physical and mechanical properties of polymer concrete using unsaturated polyester resin, initiator, heavy calcium carbonate, crushed gravel, recycled coarse aggregate, silica sand and recycled fine aggregate. The unit weight, compressive strength, flexural strength and dynamic modulus of elasticity were decreased with increasing the content of recycled aggregate. The unit weight, compressive strength, flexural strength and dynamic modulus of elasticity were showed in $2,127{\sim}2,239kg/m^3$, 80.5~88.3MPa, 19.2~21.5MPa and $254{\times}10^2{\sim}288{\times}10^2MPa$ at the curing age 7 days, respectively. Therefore, these recycled aggregate can be used for polymer concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.5
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• pp.128-135
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• 2010

Polymer-modified cement mortar(PCM) has been widely used for strengthening of the concrete structures due to its excellent physical properties such as high strength and durability. Adhesive strength or behavior, on the other hands, between PCM and concrete is very important in strengthening the concrete member using PCM. Therefore the adhesive failure mechanism between PCM and concrete should be fully verified and understood. This study was performed to evaluate adhesive strength of PCM to the concrete by the direct pull-out test. In the direct pull-out tests, the adhesive strength under the various pre-treatment conditions such as immersion, thunder shower, freezing and thawing are evaluated. Also, the field direct pull-out test are performed to investigate the adhesive strength of mock-up test specimens. In the results of the test, the adhesive strength value by field test are lower than those of the standard curing condition. From these comparison and investigation, field test result was similar with the thunder shower test result. The results of the test was used to evaluate the korean industrial standard of polymer modified cement mortars for maintenance in concrete.

• Polymer(Korea)
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• v.28 no.1
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• pp.35-40
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• 2004

The formation mechanism of void defect which deteriorate composite's property is various according to each composite process. In this paper, void formation and growth mechanism is analyzed by thermal analysis and GC/MS. We made a vacuum chamber for observing pressure effect. Thermal analysis has been done in various condition. Elements of volatiles during resin curing were turned out by GC/MS. The most of volatiles of polyester were composed of styrene (over 80%) and a small quantity of toluene. In case epoxy resin, butyl glycidyl ether was the main element of volatiles (over 90%). We concluded that the original sites of void growth existed in resin and they were eliminated by vacuum and heating process. And the growth of void was influenced by water, diluents, solvent, and reactants in resin.

• Polymer(Korea)
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• v.24 no.4
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• pp.520-528
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• 2000

New high solid acrylic resins (BMHA) containing 70% of solids content have been synthesized. The environmental friendly high solid coatings (BNHS) were prepared by using these acrylic resins and polyisocyanates. The BMHA was obtained by introducing a new functional group, acetoacetoxyethyl methacrylate (AAEM), in the copolymerization of n-butyl acrylate, methyl methacrylate, and 2-hydroxyethyl acrylate. Lowering T$_{g}$ and increasing the AAEM amount in the BMHA resulted in a high value of conversion. There was no difference in conversion with the variations of OH values. In the next step, high solid BNHS coatings were prepared by the curing reaction between BMHA and polyisocyanate at room temperature. The properties of these coatings were evaluated especially for the application of automotive top-coating materials. The introduction of AAEM in the BNHS enhanced the abrasion resistance and solvent resistance of the coatings, which indicated the possible use of BNHS coatings for top-coating materials of automobile..

• Polymer(Korea)
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• v.24 no.4
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• pp.529-537
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• 2000

The effects of the gel content on the cell structures of PP sheets by using an electron-curing system were investigated. Three extruded PP sheets crosslinked by three different doses were used for the batch foaming process with the supercritical state $CO_2$. Experiments were also performed in order to study the effects of the gel content, saturation pressure and temperature on cell structures. Then foaming conditions, such as temperature and duration of time, were changed. The amount of gas absorbed into PP samples was not affected by gel contents and the operating condition of saturation pressure, which was higher than 2000 psi. The foam cells of PP with a low gel content grew irregularly at a higher foaming temperature and for a longer duration of foaming time. However, PP samples with high gel content showed even cell structures and narrow tell size distributions under the severe conditions of high foaming temperatures and long duration of foaming time.

• Polymer(Korea)
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• v.27 no.2
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• pp.120-128
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• 2003

The effects of catalyst, accelerator and blend composition on the cure behavior of unsaturated polyester resin (UPE), vinyl ester resin (VE) and their blends were studied using differential scanning calorimetry(DSC). The DSC thermograms strongly depend on each variable. The result shows that the small exothermic peak at 115$^{\circ}C$ is due mainly to the UPE component in the UPE/VE blends and the large one at 134~138 $^{\circ}C$ is due mainly to the VE component. The results also indicate that the change of the DSC thermogram measured after each blend was exposed to high temperature 18$0^{\circ}C$ and the fast curing conditions of a few tens seconds provide useful information on understanding the thermal processing of a blend at high speed. The measurements of resin flow time represent that there are three distinct stages of cure in the UPE/VE blends: induction, transition and macro-gelation stages, as similarly reported for UPE by others earlier. The thermal stability and flexural properties of the cured UPE are significantly improved by blending it with the VE, depending on the composition.

• Polymer(Korea)
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• v.24 no.2
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• pp.228-236
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• 2000

The preparation of organophilic clay from Na$^{+}$-MMT was achieved by intercalation of alkylammonium bromide. The dispersed organophilic clay in NMP was then added to the solution of polyamic acids (BPDA-PPD, BTDA-ODA/ MPD) in NMP. After curing at 30$0^{\circ}C$, thin films of the polyimide/clay nanocomposite were prepared. The results of X-ray diffraction (XRD) shelved that the d-spacings of dried polyamic acid (PAA)-clay complexes increased in proportion to the chain length of the onium ion and patterns of two kinds of PAA-clay complexes were similar. The d-spacings of approximately 13.2 $\AA$ for the polyimide/clay nanocomposites were independent of the initial onium ion chain length and the species of PAA. From the study of XRD and transmission electron microscopy (TEM), we found layered silicates were dispersed in polyimide matrix and the resultants were intercalated nanocomposites. TGA result showed thermal stability of polyimide nanocomposite improved a little more than the pure polyimide. From the result of dynamic mechanical property, we found that the storage modulus of the nanocomposites had increased by 1.2-1.8 times of the pure polyimides.s.

• Polymer(Korea)
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• v.24 no.2
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• pp.245-251
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• 2000

A blend system prepared from epoxy(EP) and polyurethane (PU) was investigated in terms of the contact angle and mechanical properties. The contents of EP/PU were varied within 100/0~100/60 phr in the presence of 20 phr DDM (4,4'-diamino diphenyl methane) as a curing agent for epoxy resin. Contact angle measurements were performed employing a Rame-Hart contact angle goniometer. Deionized water and diiodomethane were chosen as the testing liquids. In this work, Owens-Wendt and Wu's models using a geometric mean were studied to analyze the surface free energy of blend system. For the mechanical and toughening properties of the casting specimens, the critical stress Intensity factor ($K_{IC}$) and impact test were performed. Especially, the impact test was carried out at room and cryogenic temperatures. As a result, specific or polar component of the surface free energy of the blend system was largely influenced on the addition of the PU resulting in increasing the impact strength for the excellent low- temperature performance.

• Polymer(Korea)
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• v.27 no.2
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• pp.152-158
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• 2003

Two commercial processing methods have been used to produce poly(methyl methacrylate) (PMMA) marbles; cell molding method and belt molding method. Cell molding method has low productivity and belt molding method has high equipment cost as well as high production cost. A new production method far PMMA marbles using plastic films as molds was studied in this investigation to overcome the shortcomings of cell molding and belt molding method. As plastic film molds for producing PMMA marbles, poly(vinyl acetate) film was used. A methyl methacrylate compound, which has good processability in film molding and shows good mechanical properties after curing, was prepared and used to produce PMMA marbles by film molding method. Properties of the PMMA marbles produced by film molding method were similar to, or higher than, those of commercial PMMA marbles produced by cell molding and belt molding method respectively. The film molding method is considered to have high possibility in commercial application.

• Polymer(Korea)
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• v.31 no.6
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• pp.526-531
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• 2007

This paper reports the first results of a series of planarization film study for the stainless steel (SS) substrates for flexible displays. Diglycidyl ether of bisphenol A (DGEBA) and octa(dimethylsiloxypropylglycidylether) silsesquioxane (OG) were chosen for the organic and the hybrid epoxies respectively and diaminodiphenylmethane (DDM) was used as a curing agent at 1:2 stoichiometric ratio. These materials were spin-coated on SS substrates and thermal-cured. TGA study indicated that both the pristine and the cured OG were more thermally stable than DGEBA. AFM study showed that the smooth surfaces of $1{\sim}2\;nm$ roughness can be prepared for both DGEBA and OG when the films were thick ($>\;1\;{\mu}$). The electrical properties such as dielectric constant, capacitance and the leakage current with respect to the applied voltage were all stable even after the stress of $100\;V/100^{\circ}C$ was applied for $0{\sim}10000$ seconds indicating that the insulating properties of DGEBA and OG films were very reliable.