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1995
12.
Structure-compressional property relations in carbon fibres
M.G. Dobb, H. Guo, D.J. Johnson, C.R. Park
Carbon 1995, 33 (11),
1553-1559.
November 1, 1995
Abstract
Microstructural features of carbon fibres based on both polyacrylonitrile (PAN) and mesophase pitch (MP) are discussed in relation to their compressional performance estimated by the recoil test. The compressive strength of carbon fibres is influenced by a combination of various structural features and not by any single feature. In particular, the compressive failure strength increases linearly with increasing amounts of both inter- and intracrystalline disorder. For a given amount of disorder, the more recently developed PAN-based fibres exhibited much higher compressive failure stresses than older PAN- and MP-based carbon fibres; this is due to the more homogeneous distribution of microstructural features. In order to promote compressive strength it is suggested that all crystallite dimensions should be limited to below 5 nm whilst maintaining good orientation.
DOI:
10.1016/0008-6223(95)00114-S
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1994
11.
Relationship between Characteristics and Thermal Behavior of DMSO-Solution Polymerized PANs
Byung Ghyl Min, Byoung Chul Kim, Chul Joo Lee, Tae Won Son, Chan Ho Ahn, Chong Rae Park, Yun Heum Park, Soon Sik Kim
Journal of Korean Fiber Society 1994, 31 (12),
983-992.
December 1, 1994
*Domestic Journal Article
Abstract
For both polyacrylonitrile homopolymer and copolymers(homo- and co-PANs) prepared in dimethylsulfoxide(DMSO) solution by radical polymerization induced by azo-bis-isobutyronitrile(AIBN), the thermal
behavior studied via DSC technique was discussed in relation to the characteristics of polymers. It has been
found that for the non-isothermal stabilization of homo-PANs under nitrogen and air atmospheres. the initiation and the maximum temperatures for the stabilization are not influenced by molecular weight and
molecular weight distribution characteristics of polymers. However, under isothermal stabilization under air, longer time is required by the polymers with higher content of high molecular weight fraction, i.e. Mw > 3x10^5. It has also been confirmed that the addition of comonomer and air atmosphere favour the stabilization of polymers by lowering the intiation temperature, slowing down the reaction rate, and extending the temperature range within which the stabilization may be completed. From the isothermal stabilization of co-PANs. it
was believed that the temperature of 240oC have practical significance.
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10.
Polymerization Behavior of AN in DMSO Solution
Chan Ho Ahn, Chong Rae Park, Yun Heum Park, Byung Gil Min, Tae Won Son
Journal of Korean Fiber Society 1994, 31 (11),
894-903.
November 1, 1994
*Domestic Journal Article
Abstract
For both homo-and co-polyacrylonitriles(homo- and co-PAN) prepared in dimethylsulfoxide(DMSO) solution by radical polymerization induced by azo-bis-isobutyronitrile(AIBN), the reaction kinetics was studied. It has been found that the polymerization rate increases with increasing concentrations of monomer and initiator, and the polymerization temperature, while molecular weight, polydispersity, and high molecular-weight-fraction(over 3x10^5 in Mw) decrease.
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9.
Studies on the On-line Dry-Jet Wet Spinning of Polyacrylonitrile (1) -Design Factors of Polymerization to Match Desired Spinnability-
Byung Ghyl Min, Byoung Chul Kim, Chul Joo Lee, Tae Won Son, Chan Ho Ahn, Chong Rae Park, Yun Heum Park, Soon Sik Kim
Journal of Korean Fiber Society 1994, 31 (8),
602-607.
August 1, 1994
*Domestic Journal Article
Abstract
The polymerization factors to meet the desired physical properties of polyacrylonitrile (PAN) spinning dope for on-line spinning were examined, The spinning dope was prepared by solution polymerization in
dimethylsulfoxide solution induced by azobis-iso-butyronitrile. The physical properties of the spinning dope
could be controlled by manipulating monomer concentration, initiator concentration, and polymerization temperature.
At the unusually high monomer concentrations, required in the on-Iine spinning process, the polymerization of PAN exhibited a little deviation from the theoretical prediction
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8.
Tensile-Recoil-Compressional Behaviour of Kevlar Fibers
Chong Rae Park
Journal of Korean Fiber Society 1994, 31 (6),
459-464.
June 1, 1994
*Domestic Journal Article
Abstract
The compressional behaviour of Kevlar type aramid fibres i.e. Kevlar 49, Kevlar 981, and Kevlar 149 has been studied by means of a single-fibre-recoil test method followed by scanning electron microscope (SEM) examination. The poor compressive strengths of the fibres examined are considered due to the high degree of order and their inherent pleated sheet like structures which originate from the features of nematic liquid crystalline. SEM micrographs of compressed fibres show somewhat different types of failure depending on the types of the fibres and the supporting environment around the fibres. Namely the fibres with a surrounding support exhibit essentially the formation of kink bands due to Euler bending. The difference in failure mechanisms is discussed in terms of the structural characteristics of fibre variants.
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1993
7.
[기술해설]
High Functionalization of Polyester Fibers through Physical and Chemical Modifications (2)
Tae Whan Ahn, Chong Rae Park, Yun Heum Park
Journal of Korean Fiber Society 1993, 30 (9),
617-628.
September 1, 1993
*Domestic Journal Article
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6.
[기술해설]
High Functionalization of Polyester Fibers through Physical and Chemical Modifications (1)
Tae Whan Ahn, Chong Rae Park, Yun Heum Park
Journal of Korean Fiber Society 1993, 30 (6),
403-411.
June 1, 1993
*Domestic Journal Article
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1992
5.
Preparation of Antistatic Polyester Materials and Their Properties (2) -Electrical Properties-
Yun Heum Park, Hak Soo Park, Chong Rae Park
Journal of Korean Fiber Society 1992, 29 (12),
921-929.
December 1, 1992
*Domestic Journal Article
Abstract
Various electrical properties such as electrical conductivity, electrostatic charge and its half-life time, and electromagnetic shielding effetiveness were studied for antistatic polyester film and fabric prepared by exposing modified poly( ethylene terephtalate) (M -PET) containing ferric chloride as an oxidant to pyrrole vapor. Higher content of FeCl3 led to higher eletrical conductivity, however shorter time to the saturation conductivity. It was found that just above the critical polypyrrole(PPy) content, 1.5wt% , electrical conductivity increased rapidly to the saturation value, 10^-3 S/cm. Morphological feature of the antistatic film, i. e. homogeneous and dense distribution of PPy on the film surface, was found to be another preferential factor improving the electrical conductivity. The initial electrical conductivity of antistatic film was retained even after 30 days at room temperature under atmospheric environment. As compared with the M-PET fabric itself, the antistatic fabric was found to have lower maxium electrostatic charge by about three orders and shorter half-life time by about two orders. Also the antistatic fabirc exhibited good electromagnetic shielding effectiveness which read 24 dB at 300 MHz.
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4.
Role of microvoids in aramid fibres
M. G. Dobb, C. R. Park, R. M. Robson
Journal of Materials Science 1992, 27 (14),
3876-3878.
July 15, 1992
Abstract
The distribution of microvoids in high-strength aramid fibre has been established. The tensile and compressive behaviours of both untreated and silver sulphide-impregnated Kevlar 981 fibre are reported and the results are discussed in terms of the influence of microvoids on the mechanical performance.
DOI:
10.1007/BF00545470
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3.
Preparation of Antistatic Polyester Materials and Their Properties (1) -Characterization-
Yun Heum Park, Hak Soo Park, Sung Woo Nam, Chong Rae Park
Journal of Korean Fiber Society 1992, 29 (7),
512-520.
July 1, 1992
*Domestic Journal Article
Abstract
Modified polyethylene terephtale (M-PET) was obtained by copolymerizing dimethyl terephtalate(DMT), ethylene glycol, and dimethyl 5-sulfoisophthalate(DMS) and antistatic polyester material has been prepared by exposing M-PET containg ferric chloride to pyrrole vapor. The DMS component in M-PET was confirmed by the analysis of IR and NMR spectra. The formation of polypyrrole(PPy) in M-PET matrix was also confirmed by the analysis of IR spectrum. The changes of physical structure due to the insertion of ferric chloride and formation of PPy in M-PET have been investigated by analysing wide-angle X-ray diffraction curves. The surface of the antistatic polyester film showed the continuous phase of granular PPy which was formed through the film thickness The physical properties of antistatic polyester was satisfiable, that was, the tensile strength and the elongation at break retained 80 and 90% of those of M-PET matrix, respectively. But the modulus retained about 60% of M-PET matrix.
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1990
2.
Compressional behavior of carbon fibers
M.G. Dobb, D.J. Johnson and C.R. Park
Journal of Materials Science 1990, 25 (2A),
829-834.
February 1, 1990
Abstract
The compressional behaviour of polyacrylonitrile (PAN)-based and mesophase-pitch (MP)-based carbon fibres has been studied by means of a single-fibre-recoil test method followed by scanning electronn microscope (SEM) examination. PAN-based carbon fibres have relatively high compressive strengths compared with MP-based carbon fibres. The improved tensile and compressive strengths of some recent PAN-based fibres are discussed in terms of a two-phase structure; one phase is the normal layer-plane structure, the other phase is a disordered carbon structure. The relatively low compressive strengths of the MP-based fibres are considered to be due to the high degree of order (graphitization) and their inherent sheet-like structure. SEM micrographs of compressed fibres show different types of failure depending upon the origin of the fibres. Consequently, two different mechanisms of deformation have been proposed, namely the formation of multiple kink bands associated with bending in the case of PAN-based fibres, and a single kink band associated with classical shear failure in the case of most MP-based fibres.
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1982
1.
[총설]
양모에의 그라프트 반응
Jong Lae Park, Wan Shik Ha
Journal of Korean Fiber Society 1982, 19 (3),
201-207.
June 1, 1982
*Domestic Journal Article