• Polymer(Korea)
• /
• 제34권3호
• /
• pp.198-201
• /
• 2010

We have worked a surface modification to release a strong agglomeration of multi-walled carbon nanotube(MWCNT) and a incorporation of hydrophilic polymer to improve compatibility between MWCNT and polymers. Carboxylated MWCNT was easily obtained by acid treatment and the carboxylate was converted to acylchloride by thionyl chloride. Then, we tried one more synthesizing routes to achieve covalent bonds with poly(ethylene oxide) having amine end groups of low molecular weight. We measured the polymer content on the surface of MWCNT by TGA and observed increased diameter of MWCNT by SEM and TEM analysis.

• Polymer(Korea)
• /
• 제34권6호
• /
• pp.501-506
• /
• 2010

Natural chitosan has high molecular weight and the poor solubility in water. Water-soluble chitosan with low molecular weight was prepared by the hydrolysis method. In order to develop an efficient gene delivery carrier, chitosan was conjugated with lipoic acid to form the comb-type copolymer. The copolymer with the amphiphilic property formed the self-assembled nanoparticles in the aqueous solution. The average size of nanoparticles was 217.6 nm and the average size of nanoparticles/DNA complex was 170 nm. New chitosan-lipoic acid copolymer showed the low cytotoxicity and 10 times higher transfection efficiency than that of the pure chitosan.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• 제22권11호
• /
• pp.935-940
• /
• 2009

In this research, the composites (100-x)LCP-xBNT (x = 0, 10, 20, 30, 40 vol.%) were fabricated with thermoplastic LCP(Liquid Crystal Polymer) and BNT($BaNd_2Ti_4O_{12}$) which is a high frequency dielectric material. Their dielectric properties, mechanical strength and microstructure were investigated by Impedance analyser, Instron and SEM. In order to fabricate LCP-BNT composites, LCP resin was put into the twin screw type mixer($310^{\circ}C$), melted by keeping for 10 min. After that, BNT filler was dispersed with melted LCP resin for 15 min. in the mixer. For measuring the dielectric properties and mechanical strength, Composite specimens were made by pressing composite granule (LCP-BNT) with 7 ton in the mold at $310^{\circ}C$. With increasing the BNT content (0~40 vol.%) of the composite, Its dielectric constant increased, dielectric loss and flexural strength decreased. The dielectric constant and flexural strength of composites with 20~30 vol.% of BNT filler are 4.1~6.0 and 35~55 MPa respectively. BNT/LCP composite is the potential substrate material for the high frequency application.

• Polymer(Korea)
• /
• 제27권2호
• /
• pp.129-134
• /
• 2003

It has been known that the intercalation of long alkyl chains in montmorillonites (MMT) increased the hydrophobicity as well as gallery spacing of UT, which has influenced on the exfoliation behavior of various polymers. A series of organophilic MMTs were synthesized from the water/isopropyl alcohol solution of MMT with ammonium salts of various alkyl amines. The properties of obtained MMTs such as thermal decomposition temperature, gallery spacing as well as hydrophobic property were investigated. The X-ray diffraction experiments on organophilic montmorillonite demonstrated that the increase of length of alkyl substituent resulted in increase in the spacing between silicate layers, which was ranged from 13.1 to 29.4 $\AA$. On the other hand, introduction of (di-, tri-) alkyl substituents in ammonium salts decreased water absorption of organophiplic montmorillonite to 2.7%.

• Journal of the Microelectronics and Packaging Society
• /
• 제18권2호
• /
• pp.11-15
• /
• 2011

Heat transfer equation is first reviewed and then governing equation of moisture diffusion. Analogy scheme is applied to analysis the moisture absorption problem of polymers. It make possible to numerically analyze the diffusion problem for single medium by using commercial finite element code if it is under the isothermal loading condition. It is extended to special multimaterial system by introducing pressure ratio function, whose moisture characteristics of materials are proportional to temperature only. The weight changes of silicon-nonconductive-polymer joint model due to moisture absorption is measured and been very close to the numerical results as for single media with boundary condition with zero concentration, but yields numerical errors as for multisystem media.

• Polymer(Korea)
• /
• 제29권4호
• /
• pp.321-330
• /
• 2005

In 1990's the Korean polyolefin industry boomed up through the development of magnificient polymerization catalysts. To understand the general situation of polymerization catalyst R & D, the various experimental results had been summarized for the investigation of not only the supported Ziegler-Natta catalyst used presently in polyolefin industry but also the metallocene catalysts applied for the preparation of special grade of polyolefin. In addition, it had been shown that the new polymeric materials were prepared by new developed catalyst, and the polymer in-situ nanocomposites could be obtained with the application of catalyst heterogenization procedures.

• Polymer(Korea)
• /
• 제31권5호
• /
• pp.379-384
• /
• 2007

The nanocomposites with inorganic nano powder, improved thermal stability, were prepared by urethane polymerization. The structure and surface properties of the nanocomposites were determined by X-ray diffraction and FT-IR, respectively. The thermal stabilities were studied using TGA and DSC. Their morphologies and mechanical properties were observed by SEM and UTM. As a result, the nanocomposites with MMT led to the increase of the silicate layers. The distance between layers of the nanacomposites with MMT was increased by $7.5{\AA}$ and the new peaks at $1038cm^{-1}$ were shown in the presence of the Si-O groups on the silica. The thermal stabilities of the nanocomposites were higher than those of pore polyurethane matrix. The nanocomposites had higher in mechanical properties than the pure polyurethane matrix.

• Polymer(Korea)
• /
• 제38권3호
• /
• pp.299-306
• /
• 2014

ZnO pillared saponite was synthesized via a microwave hydrolysis method. To enhance interfacial compatibility between zinc oxide (ZnO) pillared saponite and poly lactic acid (PLA), ZnO pillared organic saponite was prepared by intercalation modification of cetyltrimethylammonium bromide. Moreover, PLA/ZnO pillared organic saponite nanocomposites were prepared by melting processing. The microstructure analysis of PLA/ZnO pillared organic saponite nanocomposites showed that ZnO pillared organic saponite was exfoliated and homogeneouslydispersed in PLA matrix. The property results showed that ZnO pillared organic saponite improved the mechanical properties and thermal stabilities of PLA/ZnO pillared organic saponite nanocomposites. Differential scanning calorimetry (DSC) demonstrated that ZnO pillared organic saponite restrained the appearance of cold crystallization, lowered the glass transition temperature and melting temperature of PLA, and improved the crystallinity of PLA. The results demonstrated that ZnO pillared organic saponite had a good interfacial compatibility and heterogeneous nucleation effect in PLA matrix, and also played an active role in accelerating the crystallization process of PLA.

• Polymer(Korea)
• /
• 제38권6호
• /
• pp.726-734
• /
• 2014

Three different types of additives, thiokol, epoxidized natural rubber (ENR) and epoxidized linseed oil (ELO), were dispersed in an epoxy matrix before being used in glass fiber (GF) composites, and their effects on the mechanical and dielectric properties of epoxy resin and glass fiber reinforced epoxy composites (GF/EP) were examined. The addition of each of 7 phr ENR, 9 phr ELO and 5 phr thiokol into the epoxy resin increased the fracture toughness significantly by 56.9, 43.1, and 80.0%, respectively, compared to the unmodified resin. The mode I interlaminar fracture toughness of the GF/EP at propagation was also improved by 26.9, 18.3 and 32.7% when each of 7 phr ENR, 9 phr ELO, and 5 phr thiokol, respectively, was dispersed in the epoxy matrix. Scanning electron microscopy showed that the additives reduced crack growth in the GF/EP, whereas their dielectric measurements showed that all these additives had no additional effect on the real permittivity and loss factor of the GF/EP.

• Journal of Powder Materials
• /
• 제26권2호
• /
• pp.119-125
• /
• 2019

Piezoelectric energy harvesting technology is attracting attention, as it can be used to convert more accessible mechanical energy resources to periodic electricity. Recent developments in the field of piezoelectric energy harvesters (PEHs) are associated with nanocomposites made from inorganic piezoelectric nanomaterials and organic elastomers. Here, we used the $BaTiO_3$ nanoparticles and piezoelectric poly(vinylidene fluoride) (PVDF) polymeric matrix to fabricate the nanocomposites-based PEH to improve the output performance of PEHs. The piezoelectric nanocomposite is produced by dispersing the inorganic piezo-ceramic nanoparticles inside an organic piezo-polymer and subsequently spin-coat it onto a metal plate. The fabricated organic-inorganic piezoelectric nanocomposite-based PEH harvested the output voltage of ~1.5 V and current signals of ~90 nA under repeated mechanical pushings: these values are compared to those of energy devices made from non-piezoelectric polydimethylsiloxane (PDMS) elastomers and supported by a multiphysics simulation software.