Investigation of the coalescence phase between mesophase spheres during mesophase formation

최윤정,김지홍,이승은,이영석,임지선 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.1

The molecular weight of the pitch increases with the synthesis conditions (temperature, time, pressure). Between the components having a molecular weight more than 2,500 amu laminated by Van der Waals force, this region is called mesophase. In general, mesophase forms a bulk mesophase through the formation and growth of mesogen and coalescence between mesophase spheres. Therefore, sufficient reaction conditions for mesogen formation and proper viscosity for coalescence between mesophase spheres are important factors for forming bulk mesophase. In this paper, the mechanism of coalescence between mesophase spheres during the bulk mesophase formation is discussed. The following two mechanisms were proposed as the coalescing mechanism of mesophase spheres. 1) Polymerization of low boiling point components in pitch, 2) Reduction of isotropic area by volatilization. To visually confirm this process, mesophase pitch and isotropic pitch were mixed at a mass ratio of 8:2, 6:4, 4:6, and 2:8.

Mesophase pitch첨가에 따른 PFO의 열처리 거동에 대한 연구

김지홍,김종구,이철위,이영석,이기봉,임지선 한국공업화학회 2016 한국공업화학회 연구논문 초록집 Vol.2016 No.0

다종의 복잡한 유기화합물, 혼합물 등을 400℃ 부근에서 열처리하면 구형의 mesophase가 형성된다. Spider wedge model에 의하면 mesophase는 거대분자를 핵으로 하여 π- π 결합에 의해 적층 응집된다. 이에 거대분자가 첨가된 전구물질의 열처리 거동을 파악하고자 PFO에 mesophase pitch를 첨가한 pitch를 제조하였다. Mesophase pitch를 0~10wt% 첨가한 PFO 700g을 feed로 사용하였고, 이때 열처리 조건은 410℃, 300min으로 하였다. 반응에 대한 재현성을 확인하기 위해 3회 이상의 실험을 실시하였고, 물리적(열적)성질을 파악하기 위해 S.P, TGA 분석을, 화학적 조성을 파악하기 위해 EA, FT-IR, 불용분 분석을 실시하였다. 또한 편광현미경을 통해 mesophase의 형성 정도를 비교하였다.

메조페이스/등방성 핏치의 방사성 판단을 위한 점탄성거동

김용중,김보혜,이동훈,김창효,양갑승,이웅의,Kim, Yong-Joong,Kim, Bo-Hye,Lee, Dong-Hun,Kim, Chang-Hyo,Yang, Kap-Seung,Lee, Woong-Eui 한국섬유공학회 2010 한국섬유공학회지 Vol.47 No.4

The rheological behavior of mesophase and isotropic pitch blends were examined using capillary and coneplate viscometers to determine the spinnability. The mesophase synthesized from naphthalene and coal tar pitch modified with benzoquinone were used. The individual component of the mesophase pitch or the isotropic phase pitch showed excellent spinnability but the spinnability of the blends decreased as the composition approached 50 wt.%. The variations of the spinnability were explained based on the mechanisms of capillary break-up and cohesive brittle fracture. The fracture of the spin line was caused mainly by capillary break-up originating from the high interfacial tension between the two separated phases; the behavior was more severe in the lower shear rate region, i.e. the elasticity dominant area. The spinnability of the two phase blends could be improved by maintaining the melts under the viscosity dominant condition by adjusting the shear rate and temperature.

Influence of hot-pressing pressure on the densification of short-carbon-fiber-reinforced, randomly oriented carbon/ carbon composite

Thakur Sudesh Kumar Raunija,Sharad Chandra Sharma 한국탄소학회 2015 Carbon Letters Vol.16 No.1

The prime objective of this research was to study the influence of hot-pressing pressure and matrix-to-reinforcement ratio on the densification of short-carbon-fiber-reinforced, randomly oriented carbon/carbon-composite. Secondary objectives included determination of the physical and mechanical properties of the resulting composite. The ‘hybrid carbon-fiberreinforced mesophase-pitch-derived carbon-matrix’ composite was fabricated by hot pressing. During hot pressing, pressure was varied from 5 to 20 MPa, and reinforcement wt% from 30 to 70. Densification of all the compacts was carried at low impregnation pressure with phenolic resin. The effect of the impregnation cycles was determined using measurements of microstructure and density. The results showed that effective densification strongly depended on the hot-pressing pressure and reinforcement wt%. Furthermore, results showed that compacts processed at lower hot-pressing pressure, and at higher reinforcement wt%, gained density gradually during three densification cycles and showed the symptoms of further gains with additional densification cycles. In contrast, samples that were hot-pressed at moderate pressure and at moderate reinforcement wt%, achieved maximum density within three densification cycles. Furthermore, examination of microstructure revealed the formation of cracks in samples processed at lower pressure and with low reinforcement wt%.

Cholesteryl과 Acryloyl 그룹을 지닌 말토오스들의 열 및 광학 특성

김장훈,마영대 한국공업화학회 2004 공업화학 Vol.15 No.1

콜레스테릴 그룹을 지닌 두 종류의 말토오스 유도체, 즉 에스테르화도(degree of esterification, DE)가 3.80~4 범위에 있는 maltose 6-cholesteryl-oxycarbonylpentanoates (CMTs)와 CMTs의 아크릴산 에스테르들(CMTEs)을 제조하였다. 또한 액정 상태에 있는 CMTEs를 광가교시킴에 의해 액정 질서를 지닌 가교물질들을 제조하였다. 미가교와 가교된 시료들에 대한 열 및 광학 특성을 검토하였다. 모든 미가교 시료들은 좌측방향의 나선구조를 지닌 단방성 콜레스테릭 상을 형성하며 콜레스테릭 상을 형성하는 전 범위에서 반사색깔들을 나타냈다. 이것이 말토오스 유도체가 가시광 파장 영역에서 선택적인 반사대를 지닌 열방성 콜레스테릭 상들을 형성한다고 하는 최초의 보고이다. 모든 미가교시료들의 광학 피치들(λ_(m)′s)은 온도 상승 혹은 주어진 온도에서는 DE의 증가에 의해 감소하였다. 그러나 DE가 동일할 경우, 동일한 온도에서 나타내는 λ_(m)은 CMT가 CMTE에 비해 컸으며 가교 물질들은 반사색깔들을 나타내지 않았다. 이러한 사실은 CMTE의 콜레스테릭 구조가 가교에 의해 현저하게 변화되었음을 시사한다. Two kinds of maltose derivatives bearing cholesteryl group: maltose 6-cholesteryloxycarbonylpentanoates (CMTs) with degree of esterification (DE) ranging from 3.80 to 4 and acrylic esters of CMTs(CMTEs) were prepared. The networks with a liquid crystalline (LC) order were also prepared by photocrosslinking CMTEs in mesophase. The thermal and optical properties for both the uncrosslinked and crosslinked samples were investigated. All the uncrosslinked samples formed monotropic cholesteric phases with left-handed helicoidal structures and exhibited reflection colors over the full cholesteric range. This is the first report of a maltose derivative that formed thermotropic cholesteric mesophases with selective reflection bands in the visible wavelength region. The optical pitches (λ_(mS)) of all the uncrosslinked samples decreased with temperature or with DE at a given temperature. However. the λ_(m) of CMT was larger than that of at the same temperature and at the same DE. The networks did not display reflection colors, indicating that the cholesteric structure of CMTE were significantly changed upon crosslinking.

Lyocell 섬유 방사용액계의 유변학적 특성-N-Methylmorpholine N-oxide의 물함량의 영향-

김동복,이화섭,이영무,김병철 한국섬유공학회 2000 한국섬유공학회지 Vol.37 No.12

The hydration level of NMMO hydrates determines their solvating power to cellulose and it has a significant effect on the rheological properties of the cellulose solutions in the hydrates. NMMO hydrate with water content of 14.5 wt.% could not completely dissolve cellulose, resulting in a heterogeneous solution. the cellulose solution in NMMO hydrate with water content of 9.6 wt.% produced a mesophase. In case of $DP_{w}$ 940 cellulose solution, lower Newtonian flow region was not observed. In case of 12 and 15 wt.% $DP_{w}$ 940 cellulose solutions in NMMO hydrate with water content of 9.6 wt.%, yield behavior was observed. The yield stress of the 15 wt.% $DP_{w}$ 940 cellulose solution in NMMO hydrates with water content of 9.6 wt.% was calculated to e 6.96 Pa. Further, the orientation structure of cellulose solutions became more noticed with decreasing hydration levels of the solvent.

새로운 형태의 액정플리우레탄의 합성과 성질

이종백 ( Jong Back Lee ),강병철 ( Byung Chul Kang ),유일 ( Il Yu ) 한국공업화학회 2002 공업화학 Vol.13 No.8

다섯 종류의 새로운 형태의 액정성 폴리우레탄을 4,4`-bis(7-hydroxyheptoxy)biphenyl (BP7)와 2,6-tolylene diisocyanate (2,6-TDI), 2,5-tolylene diisocyanate (2,5-TDI), 2,4-tolylene diisocyanate (2,4-TDI), 1,4-phenylene diisocyanate (1,4-PDI) 및 hexamethylene diisocyanate (HDI)의 중부가 반응에 의해 합성하였다. 단량체 BP7은 스멕틱상을 형성하였으며 1.4PDI/BP7을 제외한 나머지 폴리우레탄에서는 모두 액정성을 나타내었다. 생성된 폴리우레탄의 구조는 IR과 ^1H NMR 스펙트럼에 의해 확인하였고 열적 성질은 DSC와 편광현미경으로 관찰하였다. Five series of novel polyurethanes were synthesized by the polyaddition reaction of diisocyanates: 2,6-tolylene diisocyanate (2,6-TDI), 2,5-tolylene diisocyanate (2,5-TDI), 2,4-tolylene diisocyanate (2,4-TDI), and 1,4-phenylene diisocyanate (1,4-PDI), hexamethylene diisocyanate (HDI) with 4,4`-Bis(7-hydroxyheptoxy) biphenyl (BP7). 4,4`-bis(7-hydroxyheptoxy) biphenyl exhibited a smectic type mesophase. All synthesized liquid crystalline polyurethanes except 1,4-PDI/BP7 exhibit liquid crystalline behavior. The structures and the thermal properties of polyurethanes were studied by using FT-IR and ^1H NMR spectroscopy, DSC measurements and a polarizing microscope equipped with a heating stage.

액정폴리우레탄의 합성 및 특성

이종백 ( Jong Back Lee ),이광현 ( Kwang Hyun Lee ),강병철 ( Byung Chul Kang ),이동진 ( Dong Jin Lee ) 한국고무학회 2009 엘라스토머 및 콤포지트 Vol.44 No.3

4종류의 새로운 형태의 열방성 액정폴리우레탄을 4,4`-Bis(5-hydroxypentoxy)biphenyl (BP5)와 2,6-tolylene diisocyanate (2,6-TDI), 2,5-tolylene diisocyanate (2,5-TDI), 및 2,4-tolylene diisocyanate(2,4-TDI), 1,4-phenylene diisocyanate (1,4-PDI) 의 중부가 반응에 의해 합성하였다. 단량체 BP5은 스멕틱상을 형성하였으며 1,4-PDI/BP5을 제외한 나머지 폴리우레탄에서는 모두 액정성을 나타내었다. 생성된 폴리우레탄의 구조는 FT-IR과 1H NMR 스펙트럼으로 확인하였고 열적 성질은 DSC와 편광현미경으로 관찰하였다. Four series of novel liquid crystalline polyurethanes were synthesized by the polyaddition reaction of diisocyanates such as 2,6-tolylene diisocyanate (2,6-TDI), 2,5-tolylene diisocyanate (2,5-TDI), 2,4-tolylene diisocyanate (2,4-TDI), and 1,4-phenylene diisocyanate (1,4-PDI) with 4,4`-bis(5-hydroxypentoxy)biphenyl (BP5). 4,4`-bis(5-hydroxypentoxy)biphenyl exhibited a smectic type mesophase. Mesophase was found for all synthesized liquid crystalline polyurethanes except 1,4-PDI/BP5. The structures and the thermal properties of polyurethanes were studied by using FT-IR and 1H NMR spectroscopy, DSC measurements and a polarizing microscope equipped with a heating stage.

새로운 형태의 액정폴리우레탄의 합성 및 특성

이종백 ( Jong Baek Lee ),이광현 ( Kwang Hyun Lee ),강병철 ( Byung Chul Kang ) 한국고무학회 2006 엘라스토머 및 콤포지트 Vol.41 No.2

비페닐기를 함유하는 새로운 형태의 액정성 폴리우레탄을 신규로 합성한 4,4`-Bis(9-hydroxynonoxy)biphenyl (BP9)와 2,6-tolylene diisocyanate, 2,5-tolylene diisocyanate, 2,4-tolylene, diisocyanate, 1,4-phenylene diisocyanate 및 hexamethylene diisocyanate의 중부가 반응에 의해 합성하였다. 단량체 BP9은 스멕틱상을 형성하였으며 1,4-PDI/BP9을 제외한 나머지 폴리우레탄에서는 모두 액정성을 나타내었다. 합성된 단량체와 중합체들의 구조는 적외선분광분석기 및 핵자기공명분석기를 사용하여 확인 하였으며, 그들의 열적 상전이 온도 및 안정성들은 시차주사 열량분석기와 편광현미경으로 조사하였다. A series of thermotropic polyurethanes containing biphenyl units was synthesized by polyaddition reaction of diisocyanates such as 2,6-tolylene diisocyanate, 2,5-tolylene diisocyanate, 2,4-tolylene diisocyanate, 1,4-phenylene diisocyanate, and hexamethylene diisocyanate with 4,4`-Bis(9-hydroxynonoxy)biphenyl (BP9). 4,4`-bis(9-hydroxynonoxy)biphenyl exhibited a smectic type mesophase. Mesophase was found for all synthesized liquid crystalline polyurethanes except 1,4-PDI/BP9 based polyurethane. Structures of the monomer and the corresponding polymers were identified using FT-IR and 1H-NMR spectroscopies. Their phase transition temperatures and thermal stability were also investigated by differential scanning calorimetry and optical polarizing microscopy.

Production of monodisperse spherical mesophase from coal tar pitch by solvent extraction

Phiciato Phiciato,Yudi Nugraha Thaha,Nono Darsono,Miftahul Huda 한국탄소학회 2023 Carbon Letters Vol.33 No.6

The spherical mesophases are the main precursors for the high tap density of carbonaceous anode batteries. However, it is challenging to control mesophase size without coalescence and no deformation since it quickly coalesces into a regular large sphere. Here, we propose a feasible extraction method to refine the spherical size of mesophase using benzene. Thermogravimetric and differential scanning calorimetry analysis of untreated pitch revealed that the maximum temperature for mesophase nucleation should not exceed 410 °C to provoke the nucleation of mesophase spheres while maintaining a high pyrolysis yield. The extraction results showed that the extraction weight tends to decrease with an increase in the solvent ratio. There is an exponential relationship between the influence of solvent ratio and the ability for extraction. The solubility of the spherical mesophase in benzene is size-dependent and can dissolve selectively spherical mesophases smaller than 5 μm. Consequently, a monodisperse spherical mesophase was obtained. The reason for forming uniform mesophase spheres can be explained by their thermodynamic state, as described by the “two-step” classical nucleation theory. Benzene effectively improves the size distribution of spherical mesophase by dissolving small sizes while retaining large ones.