• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2008.04a
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• pp.60-74
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• 2008

일반적으로 종이 도공의 바인더로 사용되는 라텍스는 입자경이 작을수록 도공층이 부동화 되기 전에 도공층 내에서 원지 혹은 도공층 표면으로의 이동 특성이 강해져서 최종 도공지의 인쇄적성에 다양한 품질의 변화를 보일 수 있다. 라텍스는 원지와 접촉하는 순간부터 원지의 특성에 따라 원지 방향으로 1차 마이그레이션이 일어나고 건조공정의 건조조건(IR-Infra Red 혹은 Hot Air Dryer)에 따라 도공층 표면으로의 2차 마이그레이션이 일어나며 이로 인해 도공층 내에서 Z-방향으로 바인더 분포가 불균일하게 분포하게 됨으로서 인쇄 모틀 현상에도 영향을 미치게 된다. 따라서 본 논문에서는 도공액의 농도와 라텍스의 입자경 그리고 건조조건에 따른 도공층의 구조변화가 최종인쇄적성에 미치는 상관성을 검토하였다.

• Polymer(Korea)
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• v.27 no.4
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• pp.358-363
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• 2003

Dispersion polymerization of acrylamide was carried out in the media of ethyl alcohol/water mixtures using hydroxypropyl cellulose and ammonium persulfate as steric stabilizer and initiator, respectively. The effects of concentrations of initiator and steric stabilizer, amount of monomer, polymerization temperature, ethyl alcohol/water ratio, and purification of monomer and nitrogen purge on the particle size of the latices and molecular weight of the polymers were investigated. The average particle diameter increased with increasing concentration of initiator, water content in ethyl alcohol/water media, and polymerization temperature, but decreased with monomer and stabilizer concentrations. The viscosity average molecular weight increased with increasing concentrations of monomer, steric stabilizer, and water content in dispersion media, but decreased with initiator concentration and polymerization temperature. The PAM polymers prepared with the purified monomer and the nitrogen purging before the reaction showed the highest molecular weight. In this study, PAM latices of 0.5∼2.4 $\mu\textrm{m}$ with 20000∼335000 in M$\_$v/ were prepared and the resulting PAM latices were all dissolved in water instantly.

• International Journal of Highway Engineering
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• v.7 no.1 s.23
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• pp.73-82
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• 2005

Linear traverse method and point count method described at ASTM have been widely used to estimate the air void system in hardened concrete. These methods, however, are rarely used at present, because they require many efforts and time consuming works. Also these results depend on each person's decision, and are not repeatable. Thus, new image analysis method using microscope and computer processes has been approached for analyzing air void system in hardened concrete. The purpose of this study was to analysis the air void systems in latex-modified concretes using a reasonable and objective image analysis method with main experimental variables such as cement types(ordinary portland cement, rapid setting cement) and latex contents(0%,15%). In the results of this study, the use of polymer latex showed that it could be attributed to its air void systems, due to the fact that the latex emulsion acts as an air-entraining agent, which thus generally guarantees an adequate air-void system.

• Applied Chemistry for Engineering
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• v.10 no.6
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• pp.889-894
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• 1999

Preparation of micron size polymer particles which have desired morphology, size, and structure by emulsion polymerization is very difficult due to coagulation of latex particles and formation of second generation particles. But there are attractive merits such as preparation of structural and functional polymer particles in seeded emulsion polymerization. Seeded emulsion polymerization of n-butyl acrylate(BA) was carried out to investigate the effects of stirring rate, reaction temperature, concentration of initiator, emulsifier, and cross-linking agent on the particle size and size distribution. By the combination of suitable reaction conditions, we succeeded in preparing $0.14{\sim}3.67{\mu}m$ diameter of poly(n-butyl acrylate)(PBA) particles using sequential seeded emulsion polymerization.

• Polymer(Korea)
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• v.24 no.5
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• pp.629-637
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• 2000

Dispersion polymerization of acrylamide in the media of t-butyl alcoho1/$H_2O$ mixtures at 30~5$0^{\circ}C$ in the presence of hydroxypropyl cellulose and ammonium persulfate as steric stabilizer and initiator, respectively, was carried out. It was studied the effects of concentrations of initiator and steric stabilizer, amount of monomer, polymerization temperature, t-butyl alcohol/$H_2O$ ratio, concentration of crosslinker, purification of monomer and nitrogen purge on the particle size of the resulting acrylamide latices and molecular weight of the latex-poly(acrylamide). In this study, poly(acrylamide) latices of 0.1~0.5 ${\mu}{\textrm}{m}$ with 470000~2080000 in (equation omitted) were prepared and the resulting PAM latices were all dissolved in water in stantly.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2003.05a
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• pp.468-473
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• 2003

유화중합은 물을 용매로 사용하기 때문에 화재와 폭발의 위험성이 없고 환경문제가 없으며 원료 원가 면에서 저렴한 특징이 있기 때문에 수요가 매년 증가하고 있는 실정이다. 이 같은 장점을 지닌 유화중합은 물을 분산매로 폴리머를 제조하는 유용한 기술이지만 유화제, 이온성의 개시제 등과 같이 폴리머 본래의 성질을 저하시키며 물에 잘 용해되는 성분을 수반한다. 따라서 이러한 기존 유화중합법의 단점을 보완한 새로운 에멀젼 라텍스 제조기술로서, 유화제 대신에 폴리비닐알콜과 같은 보호폴로이드 또는 유기 과산화물을 사용하는 무유화제 제조기법에 대한 연구가 이루어지고, 이와 같이 제조된 에멀젼 라텍스는 기존 공정에 의해 제조된 제품에 비해 내수성과 건조된 필름의 인장 강도 및 여러 매트릭스에 대한 부착력이 향상된다. 그러나 이들 방법으로 제조된 폴리머도 복합 물성이 요구되는 분야에는 한계가 있어 복합 라텍스 제조에 대한 새로운 연구가 최근에 많이 되고 있다.(중략)

• Journal of the Korea Concrete Institute
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• v.15 no.1
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• pp.95-101
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• 2003

Drying shrinkage cracking which may be caused by the relatively large specific surface is a matter of grave concern for latex modified concrete(LMC) overlay and rapid-setting cement latex modified concrete(RSLMC) overlay. LMC and RSLMC were studied for field applications very actively in terms of strength and durability in Korea. However, there were no considerations in drying shrinkage. Therefore, the purpose of this dissertation was to study the drying shrinkage properties of LMC and RSLMC with the main experimental variables such as cement types(ordinary portland cement, rapid setting cement), latex contents(0, 5, 10, 15, 20%) and curing days at a same controlled environment of 60% of relative humidity and $20^{\circ}C$ of temperature. The drying shrinkage for specimens was measured with a digital dial gauge of Demec. The test results showed that the drying shrinkage of LMC and RSLMC were considerably lower than that of OPC and RSC, respectively. This might be attributed to the interlocking of hydrated cement and aggregates by a film of latex particles, water retention due to hydrophobic, and colloidal properties of the latexes resulting in reduced water evaporation.

• International Journal of Highway Engineering
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• v.11 no.2
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• pp.185-194
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• 2009

The autogenous shrinkage of high-performance concrete, including very-early strength latex-modified concrete(VES-LMC), is generally bigger than that of normal strength concrete because of the low water/cement ratio, high binder contents, and usage of superplasticizer. Mix. proportion of VES-LMC has low water/cement ratio(0.38), high cement content(390kg/m$^3$), and aid of latex(15% of cement weight). Thus, these factors of VES-LMC, rapid water self-dissipation and evaporation within 3 hours of concrete placement would increase the autogenous shrinkage. The purpose of this study was to evaluate the early-age shrinkage, thermal deformation and autogenous shrinkages of VES-LMC with retarder contents(retarder solids-cement ratio, by weight) using to secure working time in field. The experimental results showed that retarder contents do not affect of the maximum hydration temperature. Early-age expansion of VES-LMC was mostly caused by thermal expansion and partly by autogenous expansion. The autogenous shrinkage is decreased by increasing the retarder contents within this study. On the other hand, the usage of retarder should be decided carefully considering the field conditions because an excessive usage of retarder can cause handful early-age expansion.

• International Journal of Highway Engineering
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• v.4 no.2 s.12
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• pp.1-8
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• 2002

Latex modified concrete(LMC) became to be applied as a new material for newly constructed bridge deck overlays in Korea due to its excellent bond strength, flexural strength and impermeability against water and chloride. However, it could not be adopted at repair job site because of its long curing time required. Thus, a research on latex modified concrete with rapid-setting cement(RSLMC) is necessary if it could develope the sufficient strength for early opening to traffic. This study focused on the durability of latex modified concrete with rapid-setting cement mainly on water permeable resistance and freeze-thaw resistance. The main experimental variables were latex contents(0, 5, 10, 15 and 20%) and antifoamer contents (0, 1.6, 3.2, 4.8 and 6.4%). Test results show that the permeability of RSLMC is very low indicating below 100 coulombs at 15% of latex contents at all antifoamer contents. The freeze-thaw resistance of RSLMC maintains above 90% of relative dynamic modulus at 3.2% of antifoamer content until 300 freezing-thawing cycles.

• International Journal of Highway Engineering
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• v.3 no.4 s.10
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• pp.93-103
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• 2001

This study focused on the field applicability evaluation of SB latex-modified concrete (LMC) for concrete bridge deck overlay using mobile mixer. The main experimental factors were water-cement ratio(31, 33, 35 37%), latex contents(0, 5, 10, 15, 20%), and fine aggregate ratio(55, 56, 57, 58%) in order to evaluate the workability, mechanical properties, and durability property of LMC. The slump loss, air content, compressive and flexible strength tests were used to evaluate LMC workability and strength properties. Also, the rapid chloride permeability test was used to evaluate the relative permeability of LMC. As a results, the LMC with enough workability and good quality was produced when it was mixed in field using mobile mixer, satisfying the target compressive strength and flexural strength. The required water-cement ratio of LMC for same workability when mixing with mobile mixer was less than that when mixing in laboratory. Increasing the amount of latex produced concrete with increased flexural strength by mobile mixer. The required cement-water ratios for same initial $19{\pm}3cm$ slump were 37% and 33% at laboratory and mobile mixer, respectively. The mobile mixer was accurately calibrated satisfying the required specification.