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무색투명 폴리(아미드 이미드) 공중합체의 합성 및 특성
이영도(Young Do Lee),김기수(Kisoo Kim),옥영진(Youngjin OK),김무송(Moosong Kim),장진해(Jin-Hae Chang) 한국고분자학회 2016 폴리머 Vol.40 No.2
4-nitrobenzoyl chloride와 2,2"-bis(trifluoromethyl)benzidine(TFB)를 이용하여 N,N"-[2,2"-bis(trifluoromethyl)-4,4"-biphenylene]bis(4-aminobenzamide)(TFAB)의 아민 단량체를 합성하였다. 합성된 TFAB와 무수물 단량체인 4,4"-(hexafluoro-isopropylidene) diphthalic anhydride(6FDA) 및 4,4"-biphthalic anhydride(BPA)를 다양한 몰 비로 반응하여 폴리아믹산(polyamic acid, PAA)을 합성한 후 화학적-열적 이미드화 반응을 거쳐 아미드 그룹을 가지는 폴리이미드 공중합체(Co-PI)를 합성하였다. 용액 캐스팅으로 합성된 Co-PI 필름은 유연하고 질긴 성질을 보였다. 합성된 Co-PI는 BPA의 함량 변화에 따라 열적-기계적 성질 및 광학 투명도 등을 조사하였다. Co-PI 필름의 열 팽창 계수(coefficient of thermal expansion, CTE) 값은 BPA의 몰 비가 증가할수록 감소하였지만, 광학 투명성에서는 반대의 결과를 보여주었다. N,N"-[2,2′-bis(trifluoromethyl)-4,4′-biphenylene]bis(4-aminobenzamide) (TFAB) was synthesized from 4-nitrobenzoyl chloride and 2,2′-bis(trifluoromethyl)benzidine (TFB). The obtained TFAB, 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), and 4,4′-biphthalic anhydride (BPA) were used to synthesize polyimide copolymers(Co-PIs) containing amide groups. Flexible and tough Co-PI films were prepared from poly(amic acid) (PAA) through solution-casting using chemical and thermal imidization methods. The thermomechanical properties and optical transparency of the Co-PI films with various BPA monomer contents were investigated. The coefficients of thermal expansions (CTEs) of the Co-PI films were improved linearly with increasing BPA content. However, their optical transparency was found to worsen with increasing BPA content.
최영도(Young-Do Choi),쿠로카와준이치(Junichi Kurokawa),이영호(Young-Ho Lee) 한국유체기계학회 2007 유체기계 연구개발 발표회 논문집 Vol.- No.-
The purpose of present study is not only to develop a simple method to improve pump performance but also to suppress the occurrence of cavitation in the centrifugal pump by use of J-Groove. Semi-closed impeller is a newly developed centrifugal impeller in which inlet shape of the front shroud is modified. J-Groove is a shallow groove installed on the casing wall in the meridional direction. The results show that the application of the new type impeller of semi-closed impeller with J-Groove to a centrifugal pump has proved its effectiveness as a useful countermeasure of the unstable pump performance and cavitation. The combination of semi -closed impeller and J-Groove can be applied successfully and improves both the pump performance and suction performance.
극저비속도영역에서 원심펌프의 불안정성능 개선에 관한 연구
최영도(Young-Do Choi),쿠로카와준이치(Junichi Kurokawa),김유택(You-Taek Kim),이영호(Young-Ho Lee) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-
The ratio of disk friction loss in a centrifugal pump is very large for the total pump oss in the range of very low specific speed. Therefore, impeller radius should be shortened to increase the pump efficiency because the disk friction loss is proportional to the fifth power of impeller radius. In order to compensate the decreased head by the shortened impeller radius, vane angle at impeller outlet should be increased. However, as the vane angle at impeller outlet becomes larger, performance instability occurs at low flow rate regions. In this study, J-Groove is adopted to suppress the performance instability and detailed examination is performed for the influence of the J-Groove on the pump performance. The results show that J-Groove gives good effect on the suppression of performance instability. Moreover, as J-Groove increases pump head considerably, the pump size can be smaller.