• Bulletin of the Korean Chemical Society
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• 제16권7호
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• pp.674-677
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• 1995

• 한국세라믹학회지
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• 제42권8호
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• pp.593-598
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• 2005

Polycarbosilane was synthesized by the Kumada rearrangement of polydimethylsilane in the presence of zeolite (ZSM-5) as a catalyst at $350^{\circ}C$. The prepared polycarbosilane had very low molecular weight ($M_w=500$), so that it was not suitable to fabricate SiC fiber by melt spinning. Further polymerization of PCS was conducted around $400^{\circ}C$ to obtain spinnable polycarbosilane. After polymerization, the polycarbosilanes were isolated by distillation according to the molecular weight distributions. The PCS with a controlled molecular weight distribution was spun into continuous polycarbosilane green fibers. The PCS green fiber was successfully transformed into silicon oxycarbide fiber. The room temperature strength of the SiC fiber was around 1.5 - 1.8 GPa. The oxidation behavior and the tensile strength after oxidation were also evaluated.

• 폴리머
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• 제39권2호
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• pp.235-239
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• 2015

본 연구에서는 디올 단량체로서 바이오 유래 isosorbide 및 bisphenol A가 적용된 폴리카보네이트의 단일 및 공중합체를 얻기 위한 촉매로서 LiOH, $Cu(acac)_2$ 및 n-butyltin hydroxide oxide hydrate를 각각 적용하여 용융중합 초기 단계에서 에스터 교환반응의 동력학 분석을 실시하여 촉매활성도를 비교하였다. 단일 중합의 경우, $Cu(acac)_2$가 가장 큰 촉매활성도를 나타내었으나, 서로 다른 두 가지 디올 단량체가 적용된 용융 공중합의 경우에는 촉매의 적용 메커니즘 및 단량체의 화학구조에 의존하여 LiOH의 촉매활성이 가장 큼을 확인하였다. 이러한 연구결과는 최근 관심이 집중된 바이오 유래 친환경 폴리카보네이트용 촉매선정에 활용 가능함을 제시한다.

• Bulletin of the Korean Chemical Society
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• 제17권1호
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• pp.85-87
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• 1996

• Carbon letters
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• 제15권2호
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• pp.129-135
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• 2014

Spinnable pitch for melt-electrospinning was obtained from pyrolized fuel oil by electron beam (E-beam) radiation treatment. The modified pitch was characterized by measuring its elemental composition, softening point, viscosity, molecular weight, and spinnability. The softening point and viscosity properties of the modified pitch were influenced by reforming types (heat or E-beam radiation treatment) and the use of a catalyst. The softening point and molecular weight were increased in proportion to absorbed doses of E-beam radiation and added $AlCl_3$ due to the formation of pitch by free radical polymerization. The range of the molecular weight distribution of the modified pitch becomes narrow with better spinning owing to the generated aromatic compounds with similar molecular weight. The diameter of melt-electrospun pitch fibers under applied power of 20 kV decreased 53% ($4.7{\pm}0.9{\mu}m$) compared to that of melt-spun pitch fibers ($10.2{\pm}2.8{\mu}m$). It is found that E-beam treatment for reforming could be a promising method in terms of time-savings and cost-effectiveness, and the melt-electrospinning method is suitable for the preparation of thinner fibers than those obtained with the conventional melt-spinning method.

• 폴리머
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• 제35권4호
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• pp.356-362
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• 2011

폴리카보네이트(polycarbonate, PC)에 화학적 구조가 다른 두 가지의 분지제를 첨가하여 용융중합으로 분지형 폴리카보네이트(branched PC, B-PC)를 합성하였다. 분지제의 함량은 0.001~0.005 mol% 내에서 조절하였다. 합성된 PC의 화학구조는 FTIR, $^1H$ NMR파 $^{13}C$ NMR 스펙트럼을 이용하여 확인하였으며, 분자량, 유리전이온도 및 분해온도는 GPC, DSC와 TGA를 이용하여 측정하였다. Phloro type의 분지제를 가지는 B-PC의 분자량에 낮은 값을 보여주었으며, 유리전이온도는 분자량에 따라 증가하였다. 두 형태의 B-PC 모두 선형 PC와 비교하였을 때 낮은 주파수(frequency) 영역에서 복합점도(complex viscosity)가 높게 나타났고, shear thinning 현상이 크게 나타났다. Shear thinning의 정도를 표시하는 power law index(n)는 선형회귀분석에 의해 계산되었고 0.483~0.996 범위의 값을 보여주었다. Phloro 타입의 B-PC가 높은 shear thinning 경향을 보였으며 이들 B-PC의 유변학적 특성은 동적유변측정기를 이용하여 측정하였다.

• Macromolecular Research
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• 제12권1호
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• pp.85-93
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• 2004

We have prepared poly(ethylene terephthalate) (PET) nanocomposites filled with two different types of fumed silicas, hydrophilic (FS) and hydrophobic (MFS) silicas of 7-nm diameter, by in situ polymerization. We then investigated the morphological changes, rheological properties, crystallization behavior, and mechanical properties of the PET nanocomposites. Transmission electron microscopy (TEM) images indicate that the dispersibility of the fumed silica was improved effectively by in situ polymerization; in particular, MFS had better dispersibility than FS on the non-polar PET polymer. The crystallization behavior of the nanocomposites revealed a peculiar tendency: all the fillers acted as retarding agents for the crystallization of the PET nanocomposites. The incorporation of fumed silicas increased the intrinsic viscosities (IV) of the PET matrix, and the strong particleparticle interactions of the filler led to an increased melt viscosity. Additionally, the mechanical properties, toughness, and modules of the nano-composites all increased, even at low filler content.

• Fibers and Polymers
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• 제4권4호
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• pp.156-160
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• 2003

Poly(ethylene 2,6-naphthalate) (PEN)/Poly(ethylene glycol) (PEG) copolymers were synthesized by two step reaction during the melt copolymerization process. The first step was the esterification reaction of dimethyl-2,6-naphthalenedicarbox-ylate (2,6-NDC) and ethylene glycol (EG). The second step was the condensation polymerization of bishydroxyethylnaphthalate (BHEN) and PEG. The copolymers contained 10 mol% of PEG units with different molecular weights. Structures and thermal properties of the copolymers were studied by using $^1{H-NMR}$, DSC, TGA, etc. Especially, while the intrinsic viscosities of PEN/PEG copolymers increased with increasing molecular weights of PEG, but the glass transition temperature, the cold crystallization temperature, and the weight loss temperature of the copolymers decreased with increasing molecular weights of PEG. Consequently, the hydrophilicities by means of contact angle measurement and moisture content of the copolymer films were found to be significantly improved with increasing molecular weights of PEG.

• 공업화학
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• 제5권2호
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• pp.313-320
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• 1994

로진과 말레산무수물로부터 rosin-maleic anhydride adduct(RMA)를 합성하였다. 중합반응의 단량체로서 이용하기 위한 고순도의 RMA의 합성에는 정제공정을 수반하는 용융합성법과 정제공정이 불필요한 용액합성법을 이용하였다. 용액합성법에서 합성한 RMA의 수율이 용융합성업보다 높았다. 용융합성법의 최고수율은 40%였으나 사염화탄소 및 아세트산을 반응용제로하는 용액합성법에서 얻은 생성물의 수율과 순도를 검토한 결과 비교적 고순도의 RMA를 얻을 수 있었고, 수율은 사염화탄소 용제법의 경우 48%(이론수율 87.6%), 아세트산 용제법의 경우 51%(이론수율 94%)였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.100.3-100
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• 2001

This article deals with the development of a mathematical model for the finishing polycarbonate polymerization process using a horizontal rotating disk-ring reactor with counter-current gas sweeping and the performance analysis of the reactor system by using the model. Here we intend to propose a model describing the reactor system consisting of two phases, in which by-product phenol is removed from the polymer of high molecular weight compatible with the products of commercial grades. The vapor phase is represented by a tanks-ln-series model while the polymer melt phase is regarded as a plug flow reactor.