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Cloisite 30B와 멜라민포스페이트를 함유한 Poly(oxydiethylene adipate urethane) Composites의 합성과 열분해 특성
신승욱(Seung Wook Shin),이상호(Sang Ho Lee) 한국고분자학회 2012 폴리머 Vol.36 No.5
폴리우레탄의 열적 안정성을 개선하기 위하여, poly(oxydiethylene adipate)-diol(PAD), 4,4`-MDI, Cloisite 30B(30B), melamine phosphate(MP)를 사용하여 poly(adipate urethane)(PAU)과 PAU/30B(30B 2.7 wt%), PAU/MP(MP 2.2 wt%), PAU/30B/MP(30B 2.2 wt%, MP 2.2 wt%) 복합체를 합성하고 열분해 특성을 연구하였다. PAU 복합체에서 Cloisite 30B와 MP의 분산을 안정하고 균일하게 유지시키기 위하여, adipic acid와 diethylene glycol의 에스테르 반응 단계에서 Cloisite 30B와 MP를 도입하였다. 250 ˚C 이하에서 PAU 복합체가 순수 PAU보다 더 빠르게 열분해 되었다. 고온에서는 30B와 MP에 의하여 열안정성이 개선되어 분해속도가 현저히 감소하였으며, 700 ˚C 잔량도 크게 증가하였다. In order to improve the thermal stability of polyurethane, we synthesized poly(adipate urethane) (PAU) and three PAU composites, PAU/30B (2.7 wt% 30B), PAU/MP (2.2 wt% MP), PAU/30B/MP (2.2 wt% 30B and 2.2 wt% MP), from poly(oxydiethylene adipate)-diol (PAD), 4,4`-methylene diphenyl diisocyanate (MDI), Cloisite 30B (30B), and melamine phosphate (MP). 30B and MP were introduced into the reactant mixture at the initial stage of the esterification between adipic acid and diethylene glycol, so 30B and MP were evenly dispersed in the PAU composites for long period. At temperatures lower than 250 ˚C, the PAU composites were degraded faster than pristine PAU, mainly due to the decomposition of 30B and MP. At higher temperatures, the 30B and MP enhanced the thermal stability of the PAU composites. Compared with the pristine PAU, the thermal decomposition rates of the PAU composites decreased by 13~17%. In air, the residual weights of PAU/30B, PAU/MP, and PAU/30B/MP were 2.4, 2.3, and 7.3 wt% at 700 ˚C, respectively.
RF 마그네트론 스퍼터를 이용하여 제작한 MGZO 박막의 구조적 및 전기적, 광학적 특성에 미치는 스퍼터링 전력의 영향
김인영,신승욱,김민성,윤재호,허기석,정채환,문종하,이정용,김진혁,Kim, In Young,Shin, Seung Wook,Kim, Min Sung,Yun, Jae Ho,Heo, Gi Seok,Jeong, Chae Hwan,Moon, Jong-Ha,Lee, Jeong Yong,Kim, Jin Hyoek 한국재료학회 2013 한국재료학회지 Vol.23 No.3
ZnO thin films co-doped with Mg and Ga (MxGyZzO, x + y + z = 1, x = 0.05, y = 0.02 and z = 0.93) were prepared on glass substrates by RF magnetron sputtering with different sputtering powers ranging from 100W to 200W at a substrate temperature of $350^{\circ}C$. The effects of the sputtering power on the structural, morphological, electrical, and optical properties of MGZO thin films were investigated. The X-ray diffraction patterns showed that all the MGZO thin films were grown as a hexagonal wurtzite phase with the preferred orientation on the c-axis without secondary phases such as MgO, $Ga_2O_3$, or $ZnGa_2O_4$. The intensity of the diffraction peak from the (0002) plane of the MGZO thin films was enhanced as the sputtering power increased. The (0002) peak positions of the MGZO thin films was shifted toward, a high diffraction angle as the sputtering power increased. Cross-sectional field emission scanning electron microscopy images of the MGZO thin films showed that all of these films had a columnar structure and their thickness increased with an increase in the sputtering power. MGZO thin film deposited at the sputtering power of 200W showed the best electrical characteristics in terms of the carrier concentration ($4.71{\times}10^{20}cm^{-3}$), charge carrier mobility ($10.2cm^2V^{-1}s^{-1}$) and a minimum resistivity ($1.3{\times}10^{-3}{\Omega}cm$). A UV-visible spectroscopy assessment showed that the MGZO thin films had high transmittance of more than 80 % in the visible region and that the absorption edges of MGZO thin films were very sharp and shifted toward the higher wavelength side, from 270 nm to 340 nm, with an increase in the sputtering power. The band-gap energy of MGZO thin films was widened from 3.74 eV to 3.92 eV with the change in the sputtering power.
Adipic Acid와 Diethylene Glycol의 Polyesterification에 대한 유기나노점토와 촉매의 영향
박경규 ( Kyung Kyu Park ),신승욱 ( Sung Wook Shin ),오민지 ( Min Ji Oh ),이상호 ( Sang Ho Lee ) 한국고무학회 2011 엘라스토머 및 콤포지트 Vol.46 No.1
Adipic acid(AA)와 diethylene glycol(DEG) 사이에서 일어나는 반응의 속도에 대한 유기나노점토(Cloisite 30B)의 영향을 규명하기 위하여 383K와 423 K에서 Brønsted acid인 p-toluene sulfonic acid( p-TSA)와 Lewis acid인 butylchlorotin dihydroxide를 촉매로 사용하여 에스테르 반응을 수행하였다. 촉매의 양은 전체반응물의 0.14mol%만큼 사용하였다. 반응 · 생성물의 산가로부터 계산된 전환율 vs. 시간의 자료를 사용하여 반응속도를 해석하였다. [OH]/[COOH] 초기 몰비가 2인 상태에서 수행되는 polyester-diol 합성반응의 속도는 p-TSA 촉매하에서는 AA에 대하여 2차 반응으로, butylchlorotin dihydroxide 촉매하에서는 AA에 대하여 1차 반응으로 잘 해석되었으며 두 반응의 활성화 에너지는 각각 42.2 kJ/mol, 63.8 kJ/mol이었다. AA와 DEG에 Cloisite 30B를 5 wt% 첨가시키면 p-TSA 촉매는 활성이 크게 줄어 반응속도가 매우 느려졌으며, 이 때 활성화 에너지는 72.9 kJ/mol로 높게 계산되었다. Butylchlorotin dihydroxide 촉매는 Cloisite 30B의 첨가에 관계없이 거의 일정한 활성을 유지하였다. Butylchlorotin dihydroxide 촉매하에서 Cloisite 30B를 첨가한 반응의 활성화 에너지는 61.8 kJ/mol로 Cloisite 30B를 첨가하지 않은 반응의 활성화 에너지보다 약간 낮았다. Effect of organo nanoclay (Cloisite 30B) on the polyesterification of adipic acid (AA) with diethylene glycol (DEG) was investigated with p-toluene sulfonic acid (p-TSA) (Brønsted acid) and butylchlorotin dihydroxide (Lewis acid) catalyst at 383 and 423 K. The initial [OH]/[COOH] molar ratio was two and the concentration of the catalysts in the reactants was 0.14 mol% based on the total reactants. The kinetics of the polyesterification was interpreted with the conversion data that was calculated from the acid values of the reactant-product mixture. The reaction rate of the polyesterification, which was catalyzed with p-TSA, exhibited the second-order dependency on AA concentration. When Butylchlorotin dihydroxide was used, the reaction rate revealed the first-order dependency on AA concentration. The activation energy of the reactions catalyzed with p-TSA and Butylchlorotin dihydroxide were calculated at 42.2 and 63.8 kJ/mol, respectively. Addition of 5 wt% Cloisite 30B to the reactant significantly diminished the activity of p-TSA, so the reaction rate decreased and the activation energy was calculated at 72.9 kJ/mol. Butylchlorotin dihydroxide catalyst maintained its activity regardless of the addition of Cloisite 30B to the reactant and the activation energy was calculated to 61.8 kJ/mol. Lewis acid catalyst, butylchlorotin dihydroxide, was more effective than Brønsted acid catalyst for the esterification of AA with DEG.
QoS Evaluation of Streaming Media in the Secure Wireless Access Network
Jong-woo Kim(김종우),Seung-wook Shin(신승욱),Sang-duck Lee(이상덕),Seung-jo Han(한승조) 한국정보보호학회 2007 정보보호학회논문지 Vol.17 No.2
With the increasing growth of Internet and wireless IP networks, Multimedia systems need to be envisaged as information resources where users can access anywhere and anytime. However, efficient services in these multimedia systems are open and challenging research problem due to user mobility, limited resources in wireless devices and expensive radio bandwidth. To implement multimedia services over heterogeneous network, the IP header compression scheme can be used for saving bandwidth. In this paper, we present an efficient solution for header compression, which is modified form of ECRTP. It shows an architectural framework adopting modified ECRTP when IP tunneling network using GRE over IPSec is implemented. We have conducted simulations in order to analyze the effects of different header compression techniques while delivering real-time services to the wireless access network through secured IP Network. The impacts on performance have been investigated through a series of experiments.