• Polymer(Korea)
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• v.24 no.1
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• pp.23-28
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• 2000

Autoadhesion strength of PS/PS Interfaces in solvent welding was determined as a function of processing conditions by butt joint test. It was verified that the chain mobility and surface roughness at PS/PS interface were enhanced by the applied solvent having a similar solubility parameter as PS and resulted in the dramatic improvement of autoadhesion strength at PS/PS interface. It was found that the mechanism of solvent welding is dependent upon the chain mobility due to the diffusion of solvent to PS interface and the contact area at interface. When the welding temperature is lower than the boiling point of applied solvent, the effect of chain mobility on autoadhesion strength was dominated, while contact area took more important role when welding temperature is above the boiling point of solvent. Autoadhesion strength increased with increasing contact time and contact temperature but :he effect of solvent on autoadhesion strength became smaller.

• Journal of Integrative Natural Science
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• v.4 no.4
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• pp.294-297
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• 2011

Quality of PEDOT electrode thin film vapor phase-polymerized on 3-aminopropyltriethoxysilane (APS) self-assembled monolayer (SAM) is very crucial for making an ohmic contact between electrode and semiconductor layer of an organic transistor. In order to improve the quality of PEDOT film, the quality of APS-SAM laying underneath the film must be in the best condition. In this study, in order to improve the quality of APS-SAM, the monolayer was self-assembled on $SiO_2$ surface by a dip-coating method under strictly controlled relative humidity (< 18%RH). The quality of APS-SAM and PEDOT thin film were investigated with a contact angle analyzer, AFM, FE-SEM, and four-point probe. The investigation showed that a PEDOT film grown on the humidity-controlled SAM is very smooth and compact (sheet resistivity = 20.2 Ohm/sq) while a film grown under the uncontrolled condition is nearly amorphous and contains quite many pores (sheet resistivity = 200 Ohm/sq). Therefore, this study clearly proves that a highly improved quality of APSSAM can offer a highly conductive PEDOT electrode thin film on it.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.421-426
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• 2007

A parametric study to investigate the effects of composition variables on the glass transition and mechanical properties of CNT-based nanocomposites was performed using molecular dynamics simulations. In this study, matrix chain length and CNT length were chosen as the candidate characteristic parameters. In order to understand the effect of both parameters in detail, three sample sets having different chain lengths with the same CNT configuration and two sample sets having different CNT lengths with same chain length were prepared. Other parameters such as volume fraction and density were fixed to enable rigorous comparisons. Amorphous polyethylene is used as matrix polymer and (10,0) zigzag CNT is embedded into the matrix to reinforce polymer matrix. As a result, longer polymer chain length of matrix solely increased glass transition temperature but no reinforcing enhancement was observed. CNT length showed similar increase with little enhancement of elastic modulus. In addition to this, nanocomposites showed temperature-dependent elastic modulus jump passing thorough the glass transition region agrees well with experimental results.

• Journal of the Korea Institute of Military Science and Technology
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• v.6 no.3
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• pp.44-53
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• 2003

Cu/C films were prepared at room temperature under $Cu(hfac)_2-Ar-H_2$ atmosphere in order to obtain metallized polymer by using ECR-MOCVD(Electron Cyclotron Resonance Metal Organic Chemical Vapor Deposition) coupled with a DC bias system. The room temperature MOCVD on polymer substrate could be possible by collaboration of ECR and a DC bias. Structural analysis of the films by ECR was found that fine copper grains embedded in an amorphous polymer matrix with indistinctive interfacial layer. The increase in $H_2$ contents brought on copper-rich film formation with low electric resistance. On the other hand carbon-rich films with low sheet electric resistance were prepared in argon atmosphere. The electric sheet resistance of Cu/C films with good interfacial property were controlled at $10^8$~$10^0$ Ohm/sq. ranges by the $H_2$/Ar mole ratio and the shielding effectiveness of the film showed maximum up to 45dB in the our experimental range.

• Polymer(Korea)
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• v.24 no.3
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• pp.431-436
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• 2000

To improve the thermal and mechanical properties of homo poly(L-lactic acid), DL-mandelic acid, one of the natural $\alpha$-hydroxy acid with aromatic ring as the side-chain residue was used as the comonomer. Copolymers with different contents of mandelic acid were prepared and characterized. The resulting copolymers were mostly amorphous. As the amount of mandelic acid in the monomer feed increased, the molecular weight of the resulting polymers tended to decrease linearly. T$_{g}$ and T$_{d}$ of the copolymer, however, were found to shift toward higher temperature, suggesting the improved thermal stability by increasing content of mandelic acid moiety. Tensile measurements of cast films showed somewhat improved values in the copolymers with mandelic acid content of 5 and 10 wt%.%.%.

• Current Applied Physics
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• v.18 no.11
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• pp.1300-1305
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• 2018

The tunable electronic performance of the solution-processed semiconductor metal oxide is of great significance for the printing electronics. In current work, transparent thin-film transistors (TFTs) with indium-zinc oxide (IZO) were fabricated as active layer by a simple eco-friendly aqueous route. The aqueous precursor solution is composed of water without any other organic additives and the IZO films are amorphous revealed by the X-ray diffraction (XRD). With systematic studies of atomic force microscopy (AFM), X-ray photoemission spectroscopy (XPS) and the semiconductor property characterizations, it was revealed that the electrical performance of the IZO TFTs is dependent on the concentration of precursor solution. As well, the optimum preparation process was obtained. The concentrations induced the regulation of the electronic performance was clearly demonstrated with a proposed mechanism. The results are expected to be beneficial for development of solution-processed metal oxide TFTs.

• Elastomers and Composites
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• v.37 no.4
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• pp.234-243
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• 2002

A general scheme of a rubber structure is proposed. Using the thermomechanical method(TMA), some changes in the molecular and topological structures for uncured and cured, and unfilled and filled rubbers during processing are shown. In our investigations as region it is understood a complex structure, which is expressed at the thermomechanical curve(TMC) as a zone differed from others in thermal expansion properties. This zone is between the noticed temperatures of relaxation transitions, usually on the level like those determined by DMTA at 1Hz. These regions, which shares, are not stable, and differ in molecular-weight distribution(MWD) of chain fragments between the junctions. Differences in dynamics of the formation of the molecular and topological structures of a vulcanizate are dependent on the rubber formulation, mixing technology and curing time. Some of characteristics of these regions correlate with mechanical properties of vulcanizates what is shown for NR rubbers containing ENR or CPE as a polymeric additive. It is well known that the state of order influences diffusivity of low-molecular substances into the polymer matrix. Because of this, the two topological amorphous regions should influence the distribution of the ingredients and resulting in rubber compounds' heterogeneity, and related properties of cured rubber. Investigation of this problem is expected to be, in the future, one of the essential factors in determining further improvement of polymeric materials properties by compounding with additives and in reprocessing of rubber scrap.

• Elastomers and Composites
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• v.43 no.4
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• pp.259-263
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• 2008

An effect of low-temperature long-term thermal degradation on a degree of crystallinity of a low density polyethylene (LDPE) was investigated by using $^1H$ solid state nuclear magnetic resonance (SSNMR). Firstly, the long-term thermal treatment makes a color of LDPE from white to pale yellow which is indicative of thermal oxidation. Secondly, it makes the $^{1}H$ NMR spin-spin and spin-lattice relaxation times ($T_1$) to be long. Lastly, the degree of crystallinity of the semicrystalline aged-LDPE also decreases with thermal treatment. Above all, the $T_1$ increase is envisaged to be due to either a decrease of the amorphous regions governing overall spin-lattice relaxation mechanism in LDPEs or a dynamically restricted motion of specific molecular motions by intermolecular hydrogen bonding or crosslinking. However, since the decrease of crystallinity implies an increase of amorphous regions by the thermal treatment, the former case is contrast to our results. Accordingly, we concluded that the latter effect is responsible for the $T_1$ increase.

• Journal of the Korean Ceramic Society
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• v.40 no.12
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• pp.1213-1219
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• 2003

Porous ceramics for microoganism carriers were prepared with amorphous alumina and pore formers by hydrothermal reaction, burn-out and wash-out method. Activated carbon with average size of 67,222, and 405 $\mu\textrm{m}$, organic polymer and inorganic salt were used as pore formers. Specimens were hydrothermally treated at 200$^{\circ}C$ for 24 h, heat-treated at 650$^{\circ}C$ for 5 h, and washed out at 80$^{\circ}C$ for 48 h. The formation of crystalline phase, porosity, pore size distribution and compressive strength were measured. The specimen with activated carbon was transformed to boehmite phase, but organic polymer and inorganic salt inhibited the aquohydroxoy complex gel and crystalline formation. The porous ceramics for microoganism carriers using activated carbon as a pore formers was successfully prepared, which is composed of ${\gamma}$-alumina phase with porosity of above 70 vol% and the compressive strength of 40 kgf/$\textrm{cm}^2$.

• Elastomers and Composites
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• v.38 no.4
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• pp.295-302
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• 2003

The amount of shrinkage of injection molded parts is different from operational conditions of injection molding such as injection temperature, injection pressure and mold temperature, and mold design such as gate size. It also varies depending on the presence of crystalline structure in resins. In this study, part shrinkage was investigated for various operational conditions and resins. Poly(butylene terephthalate) (PBT) for crystalline polymer, and polycarbonate (PC) and poly(methyl methacrylate) (PMMA) for amorphous polymers were used. Crystall me polymer showed higher part shrinkage by about three times than that of amorphous polymers. Part shrinkage increased as melt and molt temperatures increased, and injection pressure decreased. Part shrinkage decreased as gate size increased since the pressure delivery is mush easier for larger gate sizes. Part shrinkage at the position close to the gate was larger than that or the position far from gate. This phenomenon might be occur by difference of residual stress.