Yang-Geu Han

A new crosslinked, poly(acrylic acid)-based, dehydrating agent was synthesized through solution polymerization. The Taguchi method, a robust experimental design, was adopted to optimize the synthetic conditions based on the moisture and water absorbing capacities of the dehydrating agent. The method applied for the experiment was a standard L27 (38) orthogonal array with eight parameters and three levels. By analyzing the variance of the test results, the most effective parameters to control the

Abstract Isothermal crystallization behavior of isotactic polypropylene (iPP) synthesized using metallocene catalyst was investigated in this work. The isotacticity of the polypropylene was characterized by 13 C‐NMR spectroscopy. It was found that the melting temperature ( T m ) of the iPP is 123.51°C and the crystallization temperature ( T c ) is 93°C. The iPP synthesized in this work did not show a general increase of T m with an increase of crystallization temperature T c , due to the short c

New poly(arylene ether)s (PAEs) with both transparency and heat-resistance were prepared by a polycondensation of FBPODS, an ordered-sequence aromatic dihalide, and cardo typed aromatic diols containing fluorene and/or adamantane moiety and also non-cardo typed 1,5-naphthalene diol. The resulting polymers had their glass transition temperatures ranged from 202 to 247 ^oC. Based on TGA data, they exhibited excellent thermal stabilities, showing 5% weight loss at 434-487 ^oC. They had low thermal

New poly(arylene ether)s (PAEs) with both transparency and heat-resistance were prepared by the polycondensation of 4-fluoro-4’(((fluorobenzoyl)phenyl)-oxy)diphenyl sulfone), an ordered-sequence aromatic dihalide,and cardo typed aromatic diols that contain fluorene, adamantane, or cyclohexane moiety. The resulting polymers were found to be amorphous by X-ray diffraction, and their glass transition temperatures ranged from 194 to 245 ℃. Based on the TGA data, they exhibited excellent thermal stab

촉매인 stannous octoate 존재 하에서 글리콜리드를 이관능성 개시제인 1,4-butanediol, 1,6-hexanediol, 1,4-cyclohexane¬diol, 1,4-cyclohexanedimethanol과 반응시켜 4가지 종류의 새로운 지방족 디올을 합성하였다. 이들 새로운 디올과 succinic acid, adipic acid, 혹은 suberic acid와 titanium(IV) isopropoxide 촉매하에서 170, 190, 또는 220 ℃에서 축합중합시켜 분자구조가 규칙적으로 배열된 새로운 지방족 폴리에스테르와 무질서한 구조를 갖는 폴리에스테르를 각각 얻었다. 이들 지방족 폴리에스테르들의 유리전이온도(Tg)는 -40에서 30 ℃ 사이였다. 또한 170 ℃에서 제조된 분자구조가 규칙적으로 배열된 폴리에스테르가 높은 온도에서 합성된 구조가 무질서한 폴리에스테르들보다 Tg가 5-10 ℃ 정도 높았다. 체외분해 실험 결과, 분자구조가 규칙적으로 배열된

The side chain liquid crystal triblock copolymers (TBCs), which underwent phase transitions below their decomposition temperature, were prepared by copolymerization of poly(n-butyl acrylate) and a comonomer containing the mesogenic azobenzene group. The physical properties of TBCs in the distinctive transition temperature ranges were investigated in terms of the liquid crystal (LC) content in the copolymers. The phase transition temperatures traced optically, thermally and rheologically were wel

The relationship between k consecutive outputs of the conventional differential detector and the output of a differential detector with a k-bit delayer for a minimum shift keying (MSK) and Gaussian-filtered MSK (GMSK) system is investigated. It is shown that the output of the k-th order detector for the MSK and GMSK signal, using a k-bit delay circuit, is the product of k successive outputs of the conventional differential detector. This relationship is used to achieve performance gains over con