• Journal of the Korean Geosynthetics Society
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• v.16 no.3
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• pp.21-30
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• 2017

Cement grouting method is generally applied for the purpose of reinforcement of deteriorated reservior. Problems have been raised due to the limit of the injection material. In order to solve these problems, various grout materials have been developed. However, there are many cases in which the grounds are disturbed in actual field. In this study, the physical properties of hybrid grout with high fineness and high viscosity characteristics were analyzed to enable penetration into the ground. Optimum inflation agent was selected and mixed with the grout. The pressure and compaction effect on expansion was examined and its effectiveness was verified. From the result of confirming expansion ratio, uniaxial compressive strength, expansion pressure and compaction effect, the HI-E (2%) sample was analyzed to be excellent in improvement effect by the inflation agent. Hence, hybrid grout can be effectively applied for the impermeable and reinforcement method of deterioration reservoir and tide embankment.

• Journal of Conservation Science
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• v.28 no.3
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• pp.265-276
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• 2012

Physicochemical properties of HBA epoxy resins were controlled by varying hardener mixture and reactive diluent to improve applicability for stone conservation. The epoxy risen comprises hydrogenated Bisphenol-A based epoxide (HBA), fast curing agent (FH), slow curing agent poly(propyleneglycol)bis(2- aminopropylether) (SH) and difunctional polyglycidyl epoxide (DPE). Talc was used as an inorganic additive. The changes in viscosity and temperature during curing reactions depending on the composition of the epoxy resins were investigated. Additionally, bending, tensile and adhesive strengths were measured to identify the effective mechanical strength in stone conservation. Finally various compositions of epoxy resin/inorganic additives were developed for stone conservation by controlling cure kinetics and mechanical properties.

• Elastomers and Composites
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• v.36 no.4
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• pp.225-236
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• 2001

In order to improve the properties of the copolymer and the terpolymer that was used as removal-type pressure sensitive adhesive(PSA), we synthesized quaterpolymer with the variation of the types of monomer, initiator, and solvent, and concentration, the monomer/solvent ratio, reaction temperature and time. and determined the properties of this adhesive: the viscosity, molecular weight, conversion, solid content and structure of polymer. The prepared polymer was crosslinked by changing the type of crosslinking agent and concentration, and then we investigated the characteristics or adhesive such as peel adhesion, shear adhesion, heat resistance, weathering resistance and peel adhesion to aging. The optimum performance of RA/2- EHA/MMA/2-HEMA as a PSA were obtained when benzoyl peroxide was used as an initiator with the reactant mixture consisted of 80% BA and 2-EHA, 15%, MMA, and 5% 2-HFMA. The optimum reaction temperature and time were $80^{\circ}C$ and 8 hours, respectively. For BA/2-EHA/MMA/AA, the optimum performance was obtained when the polymerization was performed at the monomer composition of 80% BA/2-EHA, 15% MMA, and 5% AA. BPO was used as initiator and the optimum reaction temperature and time were identical to those of BA/2-EHA/MMA/ 2-HEMA. Isocyanate and melamine were used to crosslink BA/2-EHA/MMA/2-HEMA and BA/2-EHA/MMA/AA, respectively. No effect on the type of cross-linking agent on the peel adhesion was observed with aging. The quarterpolymers crosslinked with melamine left residues on the counter surface after weathering resistance test, while the polymers crosslinked with isocyanate did not.

• Elastomers and Composites
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• v.39 no.1
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• pp.71-76
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• 2004

4,4'-Methylenebis(2-chloroaniline)(MOCA) has been widely used as a crosslinking agent, but classified as a toxic chemical. Thus, its use will be limited in the near future. In this research, polyurethane coating films were prepared using 1,3-propanediolbis(4-aminobenzoate)(PDBA) as an alternative to MOCA. The base part was prepared by melting MOCA or PDBA in polyoxypropylene($M_n$=2000), followed by the addition of the various additives. The NCO-terminated toluene diisocyanate prepolymer was used as a curing agent. The polyurethane coating films were prepared by mixing the base part with the curing agent in an appropriate ratio at room temperature. The polyurethane coatings prepared using PDBA exhibited higher initial viscosity, but much longer pot lift, compared to those prepared using MOCA under the same conditions, due to lower reactivity of PDBA. The tensile strength and tear strength of the coating films were much weaker. However, the pot life, tensile strength, elongation, and tear strength of the coating films, prepared using PDBA in the presence of an increased amount of Pb(II)-octoate, were close to those of the coating films prepared using MOCA. Thus, it was concluded that PDBA can substitute MOCA in the preparation of polyurethane coatings as long as the reactivity of PDBA is enhanced using appropriate amounts of the catalyst or other appropriate catalyst.

• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.149-158
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• 2017

Permeating injection is commonly known as an ideal type of injection in grouting reservoir embankment, yet often-combined permeating and fracturing injection grouting operation can disturb the original soil. A grouting method has been regarded as effective and developed to ameliorate the possible disturbance problem. It involves compaction grouting with low expansive pressure near the injection hole and repetitive injection and compaction with grout material that allows ideal permeating injection. This thesis develops Hybrid Grout (ie. HG grout) that allows various application in any ground condition combined together, has high fineness and low viscosity, and expands permeation injection to silty sand. It researches on the injection effect of permeable compaction grout which is done with PC packer and is a combination of HG grout and expansion agent to obtain permeation compaction effect on the area near grout injection spot by developing Permeable Compaction Type Packer(ie. PC packer). As the developed PC packer, HG grout, and and expansion agent (HI-E) are applied to reservoir embankment reinforcement grouting, possibile permeation compaction effect that satisfies reservoir embankment grouting standard is confirmed according to the research.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.2
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• pp.120-129
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• 2023

Marine structures are subject to damage not only from sea salt but also from the adhesion of marine microorganisms and suspended particles, which cause additional damages. In order to prevent this, periodic coating is employed in the case of vessels to maintain the necessary performance. However, it is true that periodic coating is difficult for concrete or steel support structures, and there is a risk of marine environmental pollution. In this study, authors developed an anti-fouling coating agent using eco-friendly materials that possess hydrophilic cellulose nanofibers and AKD(alkyl ketene dimer). To achieve a homogeneous mixture, the content of cellulose nanofibers was fixed at 1 %, and AKD, distilled water, and waste glass were mixed using a digital mixer and homogenizer. The contact angle of the prepared coated surface was observed to be over 130°, indicating sufficient performance even in a water droplet flow test with a 15° slope, suggesting self-cleaning capability. Furthermore, through the analysis of viscosity characteristics at different temperatures, it was confirmed that the application is feasible at room temperature. Microstructure analysis also verified that the coating agent is uniformly applied to the concrete surface.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.388-395
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• 2016

This paper explores the photocatalytic sensitivity of cement mortar incorporated with recycled $TiO_2$ from waste water sludge. Basically, $TiO_2$ cluster sank down slowly to the bottom of cement mortar specimen before setting and hardening process. This leads the mismatch of $TiO_2$ concentration on the top and the bottom faces of a specimen. This poorly dispersed $TiO_2$-cement mortar naturally exhibits poor NOx removal efficiency especially on the top of cementitious structure. In architectural engineering application such as building or housing structures, one can simply filp over from the bottom so that more $TiO_2$ concentrated surface can be placed outward into the air. However, in highway pavement case, this could not be applicable due to in-situ installation of concrete pavement. Hence, the dispersion of $TiO_2$ cluster inside the cementitous material is getting important issue onto road construction application. To elaborate this issue, according to our results, silica fume, high-ranged water reducer, viscosity agent, blast furnace slag were not enhanced much of dispersion characteristics of $TiO_2$ cluster. The combination of foaming agent and accelerator of hardening with viscosity agent and small grain size of fine aggregate may help the dispersion of $TiO_2$ inside cementitious materials. Even though the enhanced dispersion were applied to the specimen, NOx removal efficiency doest not change much for the top surface of the specimen. This concurrently affected by the presence of tiny air voids and the dispersion of $TiO_2$ in that these voids could easily adsorbed NOx gas with the aid of large surface area.

• Restorative Dentistry and Endodontics
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• v.35 no.3
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• pp.164-172
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• 2010

During a composite resin restoration, an anticipating contraction gap is usually tried to seal with low-viscosity resin after successive polishing, etching, rinsing and drying steps, which as a whole is called rebonding procedure. However, the gap might already have been filled with water or debris before applying the sealing resin. We hypothesized that microleakage would decrease if the rebonding agent was applied before the polishing step, i.e., immediately after curing composite resin. On the buccal and lingual surfaces of 35 extracted human molar teeth, class V cavities were prepared with the occlusal margin in enamel and the gingival margin in dentin. They were restored with a hybrid composite resin Z250 (3M ESPE, USA) using an adhesive AdperTM Single Bond 2 (3M ESPE). As rebonding agents, BisCover LV (Bisco, USA), ScotchBond Multi-Purpose adhesive (3M ESPE) and an experimental adhesive were applied on the restoration margins before polishing step or after successive polishing and etching steps. The infiltration depth of 2% methylene blue into the margin was measured using an optical stereomicroscope. The correlation between viscosity of rebonding agents and mciroleakage was also evaluated. There were no statistically significant differences in the microleakage within the rebonding procedures, within the rebonding agents, and within the margins. However, when the restorations were not rebonded, the microleakage at gingival margin was significantly higher than those groups rebonded with 3 agents (p < 0.05). The difference was not observed at the occlusal margin. No significant correlation was found between viscosity of rebonding agents and microleakage, except very weak correlation in case of rebonding after polishing and etching at gingival margin.

• Applied Chemistry for Engineering
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• v.20 no.3
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• pp.258-265
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• 2009

An anionic polyurethane dispersions (PUDs) were synthesized from the poly (tetramethylene glycol) (PTMG, Mw = 2000 g/mol), mixed isocyanate of dicyclohexylmethane-4,4'-diisocyanate $(H_{12}-MDI)$ and 4,4'-diphenylmethane diisocyanate (MDI), and dimethylol propionic acid (DMPA) as anionic site, following a prepolymer mixing process. Triethylamine (TEA) was used as a neutralization agent and the ethylenediamine (EDA) as the chain extender of the prepolymer. The effects of the DMPA molar ratio and aromatic diisocyanate content in the mixed isocyanate on the particle size and viscosity of PUD were studied. Also, the mechanical and thermal properties of the PUD cast films were discussed according to the molar ratio of DMPA and aromatic isocyanate content. It was found that the particle size and the viscosity of an anionic PUD decreased with increasing DMPA molar ratio but increased with increasing aromatic isocyanate (MDI) content in the mixed isocyanate at the constant DMPA content. Tensile strength of the PUD cast films increased and elongation at break decreased with increasing DMPA content at the constant mixed isocyanate molar ratios. In thermal degradation temperature of PUD cast films, the effect of DMPA contents was great but the effect of aromatic isocyanate contents at the low DMPA content was very slight respectively.

• Applied Chemistry for Engineering
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• v.4 no.4
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• pp.823-829
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• 1993

The basic medium oil modified alkyd resin was synthesized from linseed oil fatty acid(LOFA), phthalic anhydride(PAA), trimellitic anhydride(TMA ), and trimthylol propane(TMP) by condensation polymerization at $230^{\circ}C$. TMPTA modified water-reducible alkyd resins were synthesized with TMPTA graft copolymerization onto the basic resin at $180^{\circ}C$. Acid value of the resin was controlled by the addition of TMA and N,N-Dimethylethanol amino(DMEA) was used as an neutralizing agent to prepare water-reducible alkyd. To evaluate the optimum formulation for anionic alkyd resin, water proofness and water reducibility were estimated from the acid value or TMA contents. The effect of TMPTA on the graft copoymerization of the resin was studied by measuring molecular weight, glass transition temperature(Tg), viscosity, and gel contents. The suitable balance of water proofness and water reducibility of the resin was obtained at range of 5.3~7.0wt.% of TMA contents or 40~50 of acid value of basic resin. The molecular weight, viscosity, and gel contents of water-reducible alkyd resin were increased according to the TMPTA graft copolymerization, but Tg was decreased.