• Applied Chemistry for Engineering
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• v.16 no.3
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• pp.449-455
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• 2005

Electron beam (EB) and ultraviolet (UV) curable monomers (AF-1 with mono functionality and AF-2 with tetra functionality) containing hydroxy and acrylate group for anti-fogging coating were synthesized and applied to EB and UV-curable coating systems. The synthesized reactive AF-1 and AF-2 monomers were first formulated into UV-curable system and the optimization of film properties for anti-fogging coating was investigated. The 5:17.5 ratio for AF-1 and AF-2 was found to be the best optimized formulation for anti-fogging coating without destroying the other essential properties such as hardness, solvent resistance, and adhesion. The optimized formulation was applied to the EB-curable system, and EB and UV-curable systems were compared. The results demonstrated that both EB and UV-cured films coated on PC sheet showed excellent anti-fogging properties; however, the EB-cured film exhibited better hardness, adhesion, and water repellent properties than the UV-cured film.

• Journal of the Korean Applied Science and Technology
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• v.36 no.4
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• pp.1235-1242
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• 2019

In this study, prepolymer was synthesized through the reaction of isoporon diisocyanate (IPDI) and dimethylolbutanoic acid (DMBA) based on poly (tetramethylene ether) glycol (PTMG) for the synthesis of water-soluble polyurethane to be used as a leather surface coating applied with ethyl acetate and piperazine. Thereafter, the piperazine was chain-extended with 0.01 M, 0.03 M, 0.05 M, and 0.07 M in the water-dispersed resin, and the tensile strength, elongation, CV (cyclic voltammetry), and solvent resistance analysis were performed. Tensile strength of the prepared sample was measured at 5.422 kg_f/㎟ when the piperazine content was 0.07M, and elongation was measured as 587% when the piperazine was 0.01M. Solvent resistance analysis showed the same solvent resistance regardless of piperazine content, and the redox potential was changed according to piperazine content through CV measurement.

• Journal of Adhesion and Interface
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• v.20 no.4
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• pp.146-154
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• 2019

In this study, alkoxysilane-functionalized amphiphilic polymer (AFAP), which have hydrophilic segment and hydrophobic segment functionalized by alkoxysilane group at the same backbone, was synthesized and used as a dispersant and control agent for reaction rate in the preparation of colloidally stable organic-inorganic (O-I) hybrid sols. After reaction with fluorosilane compounds, fluorinated O-I hybrid sols were prepared and coated onto glass substrate to form hydrophobic O-I hybrid coating films through low-temperature curing process. Surface hardness and hydrophobicity of cured coating films were varied with type of solvent and composition of AFAP and fluorinated alkoxysilane compounds. At appropriate solvent and composition of fluorinated alkoxysilane compounds, O-I hybrid coating film having high transparency and surface hardness could be prepared, which could be applicable to cover window of solar cell and displays.

• The Journal of Korean Academy of Prosthodontics
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• v.46 no.2
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• pp.137-147
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• 2008

Statement of problem: Dental implant procedure has been recognized as a very effective treatment to rehabilitate fully or partially edentulous patients. However, mechanical failures such as screw loosening, screw fracture have been still reported frequently. Purpose: The purpose of this study was to evaluate the influence of tungsten carbide/carbon coating, which has superior hardness and frictional wear resistance, on implant-abutment screw loosening of three different joint connections after one million cyclic loading. Material and methods: The values of detorque before and after loading were measured in three different joint connections (Osstem Implant, Korea), one external butt joint, US II implant system and two internal cones, SS II and GS II system. The values of detorque before loading was analyzed by one-way ANOVA, and two-way ANOVA and Scheffe' test were performed for the value of detorque after loading. Results: 1. The values of initial detorque of tungsten carbide/carbon coated Ti alloy screw were smaller those of Ti alloy screw (P<.01), and there were no differences among implant systems in each screw (P>.05). 2. In comparison of loss rate of detorque value after cyclic loading, US II system was greater than SS II and GS II system but there was no difference between SS II and GS II system (P<.01). 3. Loss rates of detorque value after cyclic loading decreased consistently at tungsten carbide/carbon coated Ti alloy screw comparing with Ti alloy screw in all implant systems (P<.01), and there were no differences among three systems in reduction of loss rates by using tungsten carbide/carbon coated Ti alloy screw (P>.05). Conclusion: Tungsten carbide/carbon coating to increase preload with reduction of friction resistance was a effective way to decrease screw loosening by functional loading.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.131-131
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• 2016

기원전 5000년 이집트에서부터 시작된 도금은 시간이 지남에 따라 점점 발전하여, 1900년대에 들어 전기를 이용한 도금공정이 개발되었고, 현재 뿌리산업으로써 각종 제조업에 널리 이용되고 있다. 도금 공정은 금속을 부식으로부터 보호하고, 제품의 심미성과 기능성, 생산성 등을 높이기 위해 주로 이용된다. 전주도금 공정은 완벽하게 동일한 형태의 생산품을 다량으로 제작 할 수 있기 때문에, 그 높은 생산성으로 주목 받고 있다. 특히, 나노/마이크로 크기의 정밀 소자 등을 가공하는 차세대 기술인 LIGA공정과 접목이 가능하다는 장점이 있다. 몰드를 이용하여 복제하는 방식인 전주 도금은 도금공정이 끝난 후 몰드와 완성된 제품을 분리해내는 추가공정이 필연적으로 발생하게 되는데, 둘 사이의 접착력을 낮추기 위하여 몰드의 표면에 이형박리제를 도포하게 된다. 이형박리제로는 전기가 잘 흐르면서 접착력이 낮은 이산화 셀렌이나 중크롬산이 주로 이용되지만, 원활한 박리를 위해서는 그 두께가 30 um 이상 확보되어야 하기 때문에 정밀한 미세구조 전주도금이 어렵다는 문제점이 있다. 또한 이와 같은 화학 약품들은 매우 유독하기 때문에 추가적인 폐수 처리 공정이 필요하며, 작업자의 안전을 위협하고 심각한 환경 오염을 초래한다는 추가적인 문제가 발생한다. 따라서, 매우 얇고 친 환경적이며 안전한 전주도금 이형박리제에 대한 연구가 요구되고 있다. 본 연구에서는 전주도금 몰드로 사용한 구리의 표면에 TCVD를 이용하여 단일 층 그래핀을 성장시킨 후, 그래핀이 코팅된 몰드에 구리를 전주도금하여 박리하였다. 박리 후 그래핀은 몰드에 손상 없이 남아있는 것을 Raman microscopy를 통해서 확인하였고, 몰드와 그래핀 사이의 접착력 (약 $0.71J/m^2$)에 비해 그래핀과 전주도금 샘플간에 낮은 접착력 (약 $0.52J/m^2$)을 갖는 것을 확인하였다. 이와 같이 낮은 접착력을 통해 박리 시 표면구조의 손상 없이 정밀한 구조의 미세 패턴구조를 형성할 수 있었다. 전주도금을 이용한 전극 형성과 고분자와의 융합을 통해 유연기판을 제작하여 bending 실험을 진행하였다. $90^{\circ}$의 bending 각도로 10000회 이하에서는 저항의 변화가 없었고, LED chip을 mounting한 후 곡률반경 4.5 mm까지 bending을 진행하여도 이상 없이 LED가 발광하는 것을 확인하였다. 위와 같은 전주도금 공정을 이용하여 고집적 전자기기, 광학기기, 센서기기 등의 다양한 어플리케이션의 부품제조에 활용될 수 있을 것으로 기대한다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.383-386
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• 2006

Several HTPB/AP and HTPB/AP/HMX propellants were investigated experimentally for ignition characteristics in subatmospheric pressure. The threshold ignition pressure was 4psia for HTPB/AP composite propellant. The partial replacement of AP in HTPB/AP composite propellant by $5\sim15%$ of HMX, HNIW showed improvements in the threshold pressure was below 0.4psia. This appears to be due to the exothermic dissociation characteristics of HMX and HNIW at lower temperature $(\sim220^{\circ}C)$ than that of AP. The ignition substance B/KNO3 was coated thinly on the propellant surface for better ignition effect. As a result, ignition delay time of 15% was improved. NC is applied to $B/KNO_3$ ignition substance as a secondary binder and $NC-B/KNO-3$ suspension solution is coated to the propellant surface.

• Journal of the Korean Applied Science and Technology
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• v.31 no.1
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• pp.74-82
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• 2014

For this research, prepared ammonium dihydrogen phosphate aqueous solution and polyurethane dispersion. Use these resin, this article has been analyzed about change of mechanical properties by increasing amount of ammonium dihydrogen phosphate aqueous solution in polyurethan resin on coated leather and dried film. According to measure data for solvent resistance, DPU(polyurethane dispersion) resin and DPU-AD1, D2, D3(samples of polyurethaneresin with ammonium dihydrogen phosphate aqueous solution) had good property. As known in the results, increase of ammonium dihydrogen phosphate constant did not influence to big change of polyurethane resin properties. As test of tensile strength, DPU had highest tensile characteristic($3.114kg_f/mm^2$) and DPU-AD3 had lowest tensile characteristic($2.510kg_f/mm^2$). As same as tensile characteristic, abrasion test determined DPU(50.5 mg.loss) had highest properties. In elongation case, DPU had best properties(602 %) in this experiment.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2001.04a
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• pp.158-158
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• 2001

산업용 포장재의 주원료로서 이용되고 있는 국산골판지고지(KOCC)는 반복적인 재활용 으로 인하여 섬유장이 짧고 매우 각질화된 상태이며, 펄프 내 미세분 함량이 50%이상에 달 하고 있다. 또한 섬유의 표면이 인쇄잉크, stickies 및 각종 이물질로 오염됨에 따라, 섬유자 체가 보유하고 있는 섬유간 결합 능력이 저하된 상태이다. 국산 골판지 고지를 재활용한 골판지 원지의 생산 시 탈수성 및 강도 저하의 단점을 극 복하는 것은 생산성과 품질향상의 측면이외에 고지 재생을 촉진시킨다는 의미를 지니고 있다. 상기한 KOCC의 단점을 극복하는 방안으로 섬유분과 미세분의 적절한 분급을 통하여 초지 시 탈수저향을 감소시키고 더불어 종이의 강도를 개선하는 방안이 본 연구센터에 의해 고안되었다. 아울러 고온압착건조 처리를 활용한 종이의 물성 개선법이 국내에 이미 적용된 상태로 건조시간의 단축 및 종이의 제반물성을 개선시켜주게 되었다. 하지만 이미 열화된 KOCC에 고온압착건조 처리를 적용하여 밀도를 증가시킨다 할지라 도 천연의 UKP를 이용한 종이에 준 하는 강도를 얻는 데에 한계가 있었다. K KOCC 펄프의 섬유간 결합 능력을 개선시키기 위하여 본 연구에서는 Kneading처리와 지력증강제를 첨가를 함께 실시하는 방안을 검토하였으며, 고온압착건조된 골판지 원지의 표면에 코팅처리를 실시하여 그 효과를 분석하였다. 이를 통해 국산 골판지고지를 재활용한 골판지원지의 강도 극대화 방안을 탐색하고자 하였다.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.3
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• pp.67-72
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• 2006

Several propellants were investigated experimentally for ignition characteristics in subatmospheric pressure. The threshold ignition pressure was 4 psia for HTPB/AP composite propellant. The partial replacement of AP in HTPB/AP propellant by $5{\sim}l5%$ of HMX, HNIW showed that the improvements in ignition delay was over 50% and the threshold pressure was below 0.4 psia. This appears to be due to the characteristics of HMX and HNIW exothermic dissociated at the temperature(${\sim}220^{\circ}C$) love. than that of AP. The ignition substance $B/KNO_3$ was coated thinly on the propellant surface for better ignition performance. As a result, ignition delay time of 15% was improved. NC is applied to $B/KNO_3$ ignition substance as a secondary binder and $NC-B/KNO_3$ suspension solution is coated to the propellant surface.

• Journal of the Korean Vacuum Society
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• v.16 no.2
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• pp.79-90
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• 2007

Prototype of $800{\ell}$ vacuum web coater (Vic Mama) consisting of ion source with low energy less than 250 eV for high speed surface modification and 4 magnetron sputter cathodes was designed and constructed. Its performance was evaluated through fabricating the adhesiveless flexible copper clad laminate (FCCL). Pumping speed was monitored in both upper noncoating zone pumped down by 2 turbo pumps with 2000 l/sec pumping speed and lower surface modification and sputter zone vacuumed by turbo pumps with 450 1/sec and 1300 1/sec pumping speed respectively. Ion current density, plasma density, and uniformity of ion beam current were measured using Faraday cup and the distribution of magnetic field and erosion efficiency of sputter target were also investigated. With the irradiation of ion beams on polyimide (Kapton-E, $38{\mu}m$) at different fluences, the change of wetting angle of the deionized water to polyimide surface and those of surface chemical bonding were analyzed by wetting anglometer and x-ray photoelectron spectroscopy. After investigating the deposition rate of Ni-Cr tie layer and Cu layer was investigated with the variations of roll speed and input power to sputter cathode. FCCL fabricated by sputter and electrodeposition method and characterized in terms of the peel strength, thermal and chemical stability.