The thermotropic liquid crystalline behavior of mesophase pitches with different chemical structures

Title
The thermotropic liquid crystalline behavior of mesophase pitches with different chemical structures
Authors
김병철
Keywords
COAL-TAR PITCH; AROMATIC-HYDROCARBONS; CARBON-FIBERS; RHEOLOGICAL BEHAVIOR; PETROLEUM PITCHES; SOLUBLE MESOPHASE; RODLIKE PARTICLES; CARBONIZATION; NAPHTHALENE; FLOW
Issue Date
2015-01
Publisher
PERGAMON-ELSEVIER SCIENCE LTD
Citation
CARBON, v. 81, Page. 694-701
Abstract
Chemical structure-dependent liquid crystalline behaviors of two commercial mesophase pitches, M-AR and T-MP, which are synthesized with different raw materials of naphthalene and coal tar, respectively, were comparatively examined. The NMR analysis together with preparation procedure enabled us to suggest that M-AR consisted of linear semi-rigid molecules and T-MP, irregularly shaped rigid molecules. Between 320 and 370 degrees C M-AR showed marbled texture whereas T-MP, a change from schlieren/marbled to schlieren texture. WXRD results indicated that M-AR exhibited a gradual change of d(002) and L-c with temperature but T-MP, a drastic change. A point shear stress made M-AR produce oriented flow domains but T-MP retained schlieren texture even in the oriented structure. In the temperature range producing biphase, M-AR showed a shoulder on the plot of viscosity versus temperature but T-MP, a peak. As temperature was increased M-AR gave an increase of loss tangent but a decrease of yield stress while T-MP gave a saturation point at 330 degrees C, at which temperature loss tangent was maximum and yield stress was minimum. Both mesophase pitches gave viscosity curves matched with the Asada-Onogi model. In the temperature range producing dispersed polydomain system, however, T-MP showed almost shear rate-independent plateau while shear-dependence was observed in M-AR. (C) 2014 Elsevier Ltd. All rights reserved.
URI
http://www.sciencedirect.com/science/article/pii/S0008622314009695http://hdl.handle.net/20.500.11754/22090
ISSN
0008-6223; 1873-3891
DOI
http://dx.doi.org/10.1016/j.carbon.2014.10.007
Appears in Collections:
COLLEGE OF ENGINEERING[S](공과대학) > DEPARTMENT OF ORGANIC AND NANO ENGINEERING(유기나노공학과) > Articles
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