• Elastomers and Composites
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• v.56 no.1
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• pp.6-11
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• 2021

In order to develop an ultra-high-density elastomeric material for substitution of steel dynamic dampers, a new curing system and technique for high-loading of the filler were examined in this study. Mechanochemical modification of chloroprene rubber (MAH-g-CR) using an internal mixer was carried out with maleic anhydride (MAH) as a reactive monomer. The optimum amount of MAH was 10 phr and the efficient grafting of MAH on CR could be achieved at a mixing temperature of 100℃. After preparing MAH-g-CR, 50 mol% epoxidized natural rubber (ENR 50) was blended with MAH-g-CR to develop a "self-curable rubber blend system" via reaction between the functional groups of the elastomeric matrices without the curing agent and additives. The content of ENR 50 was fixed at 30 wt.% throughout evaluation of the curing behavior of the MAH-g-CR/ENR blend. Tungsten powder was added to the MAH-g-CR/ENR matrix up to 60 vol.% to obtain ultra-high-density, and the maximum density obtained was 7.57 g/㎤. Stable ts2 (scorch time) and t90 (90% cure time) could be obtained even when tungsten powder was incorporated up to 60 vol.%. In addition, the tensile strength and damping properties of MAH-g-CR/ENR containing 60 vol.% of tungsten were better than those of CR containing 60 vol.% of tungsten.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2001.11a
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• pp.21-27
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• 2001

Epoxy/BaTiO$_3$composite film type capacitors with excellent stability at room temperature, uniform thickness, and electrical properties over a large area were successfully fabricated. We fabricated composite capacitor films with good film formation capability and easy process ability, from ACF-resin as a matrix and two kinds of BaTiO$_3$powders as fillers to increase the dielectric constant of the composite film. The crystal structure of the powders and its effects on dielectric constant of the films were investigated by X-ray diffraction. DSC and dielectric properties tests were conducted to decide the right curing temperature and the optimum amount of the curing agent. As a result, the capacitors of $7{\mu}{\textrm}{m}$ thick film with 10nF/cm2 and low leakage current were successfully demonstrated.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.913-918
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• 2001

This paper investigates insulating effects and strength properties of concrete under cold climate carrying out the experiment with insulating forms on the slab member. According to test results, under $-10^{\circ}C$ of outer temperature, the surface of concrete exposed to outer temperature goes below zero after 10hours since exposed. And, the surface of concrete covered with vinyl and blanket goes below zero after 42hours. However, the surface of concrete covered with insulating materials such as polystyrene foam does not drop below zero until 55hours. And, according to coring sample strength test, compressive strength cured with insulation shows much higher strength than no insulation curing condition and vinyl and blanket curing condition.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.79-84
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• 2002

We carried out the feasibility study of super early self compacting concrete having the characteristics of 1 day demoulding without steam curing, high flowable concrete with self compacting, high strength and high durability etc. Here, We test and selected by several methods using high early cement with and without admixtures for the condition of super early strength self compacting concrete's manufacture (SSCC). we sucessed to meet at the goal of SSCC with 20-35N/mm$^2$ at 1 day, without steam curing and with slump flow about 60-65cm. We continue to search the effectual conditions of SSCC's manufacture by changing mix designs, several of admixture (superplasticizer, stabilising agent), slag, fly ash, high early cement and apply the products for practical use.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.628-631
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• 2004

In this paper, mechanical properties of concrete incorporating CKD are discussed with W/B and fluidity. For setting properties, an increase in W/B retarded setting time greatly in $5^{\circ}C$, while accelerated in $20^{\circ}C$. For fluidity, an increase in slump delayed the setting time with dosage of SP agent. The presence of CKD has little influence on setting time compared with plain concrete. For compressive strength, an increase in maturity enhanced compressive strength. Fluidity had no relation to compressive strength. At low curing temperature, concrete with CKD has slight strength loss compared with plain concrete. However, remarkable strength loss at low curing temperature in early stage was not found, which can be applicable to low temperature environment concrete placing.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.129-129
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• 2006

Conventional solvent-based polyurethane (PU) is well established for wide applications, such as textile treatments, surface coating, adhesive and so on. Due to the demands of safety, economic, and environmental protection, the solvent-based PU is restricted and has been phasing out and aqueous-based PU is becoming the world market trend, which is an environmental friendly product. The chemical resistance, physical and mechanical properties of aqueous-based PU are still not competible with solvent-based PU. Because of aqueous-based PU is a linear thermoplastic polymer with lower average molecular weight. Their improvements are normally performed by a post-curing reaction or a polymer hybridization to enhance the polymer cross-linking density. Hybridization of PU with aqueous-based epoxy resin or acrylate emulsion and then cured by a curing agent for improving the performance properties and reducing the cost of aqueous-based PU.Furthermore, a special function is added to aqueous-based PU increasing the application value, for examples, flame retardation, polymeric dyes, hydrophilic and etc.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.555-558
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• 2000

It has been increasingly proving in interest of environment pollution around the world. so, recycling of waste resources are seriously taken into consideration. Great deal of coolant for the car have been wasted for along time. due to the end of life time of them. Therefore, validities of wasted coolant as an agent for concrete are described in this paper. Mechanical properties of concrete using coolant wastes is investigated. As contents of coolant wastes increase, slump and slump flow decrease, while air content show reverse tendency. setting time shows to be accelerated with increase of waste contents. As for the effect of low curing temperature, low curing temperature increase compressive strength with increase of coolant waste. Application of coolant waste to cold weather concrete is considered to achieve favorable effects.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.337-342
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• 1999

The Purpose of this study is to evaluate the strength characteristics of polyurethane(PUR) mortar cured under low temperature condition. PUR mortars are prepared with various catalyst content, methylene chloride(MC) content as a viscosity reducing agent, and curing age at low temperature condition of $0^{\circ}C$, -5$^{\circ}C$ and -1$0^{\circ}C$, tested for working life, compressive and flexural strengths. From the test results, the catalyst and MC contents affect the degree of hardening and blowing of PUR mortar. Strengths increase with an increasing catalyst content at low temperature. Flexural and compressive strength of PUR mortar are about 177kgf/$\textrm{cm}^2$ and 490kgf/$\textrm{cm}^2$ respectively at curing temperature of -1$0^{\circ}C$ with catalyst content of 0.4%. Therefore, it is apparent that this PUR mortars have a sufficient strengths for repair of concrete structures.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.469-472
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• 2006

Amount used of admixture fare is increasing for concrete economic efficiency and ability security. Security of economic efficiency and ability can expect by use of this admixture fare but is displaying a lot of problems on early age strength hold by hydrate delay relatively. Specially, in the case of construction site, concrete strength can speak that interrelation is high with mold removal of forms time. Therefore, is economical and need examination of plan that can secure robber within 3 days using admixture fare such as fly ash and blast furnace slage differential speech to secure function. In this study, adding liquid admixture within 1% of a binding agent quantity to examine these problem with physical characteristic after hardening ago specially, strength change at standard and air dry curing of observed change in priority. Air dried and water curing total strength enhancement effects appeared by thing which is in case of add test result liquid admixture by below 1% and strength deputy by passage of age could know is not big.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.333-334
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• 2010

In this paper, quality variations of commercially available anti-freezers manufactured in Korea are studied. This study is focused on the effect of the use of anti freezer on strength recovery of cement mortar under low curing temperature. As expected, regardless of types of anti freezer, the use of antifreezer protects the water from freezing under low curing temperature.