17,403 research outputs found
Study on morphology evolution, orientational behavior, and anisotropic phase formation of highly filled polymer-layered silicate nanocomposites
No full textMorphology evolution, anisotropic phase behavior, and orientational behaviors of the highly filled polymer-organically modified layered silicate nanocomposites are investigated by using synchrotron small-angle X-ray scattering (SAXS), transmission electron microscopy (TEM) and polarized light microscopy (PLM). Two kinds of polymers, maleated polypropylene and maleated polyethylene were used as a matrix polymer. The final morphology of both polymer-organically modified layered silicate nanocomposites evolves via four stages; intercalation, dual states of intercalation and exfoliation, ordered exfoliation, and disordered exfoliation in sequence as the concentration of silicate decreases in the nanocomposites. The morphology evolution of nanocomposites is determined by balancing an interaction between polymer and silicate against interactions between silicate platelets such as a steric interaction and an attractive interaction, which depends on the concentration of silicates. Both the nanocomposites show the optical anisotropy above 12 vol % clay originating from the ordering of silicate layers. The layered silicates subjected to shear flow show the orientation behavior that the silicate platelet's normals are perpendicular to the flow direction. Degree of orientational order changes with the concentration as well as shear rate in a complex manner. Up to an intermediate concentration, the extent of order is enhanced with the clay concentration. In contrast, at high concentrations, the extent of order decreases or increases according to the type of nanocomposite. The differences are discussed through the consideration of the morphology, the particle-particle interaction, and the rheological property of the nanocomposites.This work was supported in part
by Brain Korea 21 program and in part by the Center
for Advanced Functional Polymers. We thank Doc. J.
M. Park in Samsung General Chemicals for allowing
the use of the cryogenic ultramicrotome and Doc. C. H.
Kim in Honam Chem. Co. for providing the materials.
Experiments at PLS were supported in part by MOST
and POSCO
Phase behavior, crystallization kinetics, and morphology of monotropic liquid crystalline poly(ester-imide)s with a decamethylene spacer
No full textThe phase transition, crystallization kinetics, and morphology of monotropic liquid crystalline poly(ester-imide)s are investigated by synchrotron X-ray diffraction, differential scanning calorimetry (DSC), polarized light microscopy (PLM), and transmission electron microscopy (TEM). Synchrotron X-ray diffraction and DSC results show that the polyester-imide) with methyl side pendant group (10M) exhibits monotropic nematic and smectic A phases upon cooling from the isotropic melt, followed by a crystalline phase (crystal E structure). The results of isothermal crystallization kinetics show that the crystallization rate is faster in the smectic phase than in the nematic phase and the slowest in the isotropic phase. It is found that the crystallization in the nematic phase leads to lamellar decorated disclination structures upon TEM observation, indicating that the enhancement of nucleation dominates the acceleration of crystallization. Polyester-imide) without side pendant group (10H) forms only a crystalline phase upon cooling. However, the air-quenched sample shows a threadlike texture. TEM observation further reveals the trace of nematic disclination structures, confirming that the crystallization proceeds through nematic phase. In contrast, the sample, cooled with a slow cooling rate of 5 degreesC/min, exhibits the spherulite structure. The morphological variation of the polyester-imide) is discussed on the basis of competition between primary nucleation and crystal growth.This work was supported in part
by the Korea Science & Engineering Foundation (KOSEF) through Engineering Research Center (ERC) and
in part by the Brain Korea 21 program. Experiments
at Pohang Light Source (PSL) were supported in part
by MOST and POSCO
Electron Kinetic Property of a Magnetized Dual-Frequency Capacitively-Coupled Plasma
No full textSpatially-resolved electron-energy-distribution functions (EEDFs) of a magnetized dual-frequency (60 and 2 MHz) capacitive discharge are numerically investigated by using a one-dimensional particle-in-cell/Monte Carlo collision simulation. It is shown that the electron kinetic property over the entire energy range changes from a nonlocal to a local regime, as the magnetic field increases. This transition results from a reduction in the electron diffusion in coordinate space and an enhancement of the electron diffusion in energy space due to an increase in the magnetic field. In an asymmetric discharge, it is found that the electron kinetic property near the 2 MHz electrode, which has a smaller electrode with an external capacitor, is more localized than that near the 60 MHz electrode.X111sciescopuskc
A statement of the views of the Chinese government on the report of the Commission of enquiry of the League of nations: By His Excellency Dr. V. K. Wellington Koo
No full textGeneva: Chinese delegation to the League of nations, 1932. 46 p., 1 l ; 23 cm. Cover title: Views of the Chinese government on the Lytton Report. Contents: pt. I. Statement delivered by Dr. V. K. Wellington Koo at the meeting of the Council of the League of nations held at Geneva on November 21st, 1932.--pt. II. Concluding remarks of Dr. Koo's statement to the Council of the League of nations at its meetingin Geneva on November 24th, 1932. Persistent link to this record: https://encore.qub.ac.uk/iii/encore_qub/record/C__Rb111440
Mechanical and rheological properties of the maleated polypropylene-layered silicate nanocomposites with different morphology
No full textThree types of maleated polypropylene-layered silicate nanocomposites with different dispersion states of layered silicate (deintercalated, intercalated, and exfoliated states) are prepared from two kinds of polypropylenes with different molecular weights, organically modified layered silicate and pristine montmorillonite to investigate the effect of the final morphology of the nanocomposite on the rheological and mechanical properties. Maleated polypropylene with high molecular weight intercalates slowly and the other with low molecular weight exfoliates fast into the organophilic layered silicates. Rheological properties such as oscillatory storage modulus, nonterminal behavior, and relative viscosity has close relationship with the dispersion state of layered silicates. The exfoliated nanocomposite shows the largest increase and the deintercalated nanocomposite shows almost no change in relative shear and complex viscosities with the clay content. The exfoliated nanocomposite shows the largest drop in complex viscosity due to shear alignment of clay layers in the shear flow. In addition, the final dispersion state of layered silicates intimately relates to the mechanical property. The dynamic storage moduli of nanocomposites show the same behavior as the relative shear and complex viscosities. (C) 2003 Wiley Periodicals.This work was supported in part by the Brain Korea 21
program and in part by the Center for Advanced Functional
Polymers. The authors thank Chang-Hyeon Kim and the
Honam Chemical Corporation for providing maleated
polypropylene resin. This experiment at PLS (Pohang Light
Sources) was supported in part by MOST and POSCO
Characteristics of polyvinylpyrrolidone-layered silicate nanocomposites prepared by attrition ball milling
No full textPolyvinylpyrrolidone (PVP)/sodium montmorillonite (MMT) nanocomposites prepared via the solution intercalation method were investigated by UV/vis, SEM, X-ray diffraction, TEM, FT-IR and PLM (polarized light microscopy). PVP/MMT nanocomposites show exfoliation below 20 wt% MMT and intercalation above this concentration. Nanocomposites retain good optical clarity and increased thermal resistance with MMT content. The compatibility between PVP and MMT and their enhanced properties may be explained by hydrogen bonding interactions. In addition, the nanocomposites prepared under more rigorous mixing conditions show better transparency because the smaller particle sizes are induced. In addition, the study on optically clear PVP/MMT suspensions helps one to understand how optical anisotropy of MMT is affected by the existence of polymer in. aqueous solution. (C) 2002 Elsevier Science Ltd. All rights reserved.This work was supported in part by Brain Korea 21
program and in part by the Center for Advanced Functional
Polymers. We thank Samsung General Chemicals for
allowing the use of the cryogenic ultra-microtome
Nomos α
No full textNomos Alpha' features 20 pen drawings (each 27.5 x 22.5 cm) from the book 'R', published by Swiss Re in 2006. Conceived on the occasion of the Korean Cultural Centre UK's 2016 artist of the year exhibition 'Koo Jeong A: Riptide' (7 October - 19 November 2016), 'Nomos Alpha' features the 20 exhibited works by the artist. Curated by Je Yun Moon, 'Riptide' included artistic responses to Koo Jeong A's drawings by Kyung Roh Bannwart, Melissa Dubbin & Aaron S. Davidson, Yva Jung, Hanqing Ma & Mona Yoo, Martin Roth and Matthias Sohr. Signed and numbered on a bespoke embossed back cover, the book is published in a limited edition run of 500. Produced on extra thick paper with a semi-translucent jacket, this little book is a work of art in itself. Koo Jeong A's often humorous drawings recall childlike simplicity yet express an underlying complexity. Exhibition: HENI Gallery, London, UK (18.5. - 23.5.2018
Morphology evolution and anisotropic phase formation of the maleated polyethylene-layered silicate nanocomposites
No full textMorphology evolution and anisotropic phase formation of the maleated polyethylene-layered silicate nanocomposites are investigated by using synchrotron small-angle X-ray scattering (SAYS), transmission electron microscopy (TEM), and polarized optical microscopy (POM). Despite favorable compatibility between polymer and organically modified layered silicates, the final morphology of the nanocomposite evolves via four stages: disordered exfoliation, ordered exfoliation, dual morphologies of intercalation and exfoliation, and intercalation in sequence with the content of silicate. The formation of the ordered exfoliation state is attributed to the steric interaction between anisotropic silicate plates. Particularly, the transition from exfoliation to intercalation provides us with the significant clue that the interaction between layer silicates gets dominant when the distance between them is smaller than a certain value. It is found that the silicate layers need larger layer spacing than 9 nm to avoid the attractive interaction between adjacent silicate layers and to keep the exfoliation state in this nanocomposite system. Additionally, the nanocomposite shows the optical anisotropy above 12 vol % clay due to the ordering of silicate layers. The optical anisotropy becomes stronger with the content of silicate.This work was supported by the
Brain Korea 21 program and the Center for Advanced
Functional Polymers in Korea Advanced Institute of
Science and Technology. We thank Samsung General
Chemicals for allowing the use of the cryogenic ultramicrotome
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