• Journal of Adhesion and Interface
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• v.25 no.1
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• pp.152-156
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• 2024

We conducted research on a two-component epoxy adhesive material based on acid graft polyolefin using maleic anhydride to address the lack of formability due to epoxy adhesives' hard segments. To understand the graft efficiency according to reaction conditions, we conducted studies based on polyolefin molecular weight, initiator half-life, and initiator concentration for each process. The maleic anhydride grafted polyolefin produced was used as an adhesive material for aluminum and CPP film lamination after mixing with epoxy hardener. The graft efficiency in the solution process was approximately 30% superior to that in the melt process, and an increase in graft ratio confirmed an increase in peel strength.

• Macromolecular Research
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• v.17 no.6
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• pp.378-387
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• 2009

This research compared three methods for producing and processing nanocomposite polypropylene filament yarns with permanent antimicrobial efficiency. The three methods used to mix antimicrobial agents based on silver nano particles with PP were as follows: 1) mixing of PP powder and inorganic nanocomposite filler with the appropriate concentration using a twin-screw extruder and preparing granules, 2) method 1 with a singlerather than twin-screw extruder, and 3) producing the masterbatch by a twin-screw extruder and blending it with PP in the melt spinning process. All pure polypropylene samples and other combined samples had an acceptable spinnability at the spinning temperature of $240^{\circ}C$ and take-up speed of 2,000 m/min. After producing as-spun filament yarns by a pilot plant, melt spinning machine, the samples were drawn, textured and finally weft knitted. The physical and structural properties (e.g., linear density, tenacity, breaking elongation, initial modulus, rupture work, shrinkage and crystallinity) of the as-spun and drawn yarns with constant and variable draw ratios (the variable draw ratio was used to gain a constant breaking elongation of 50%) were investigated and compared, while DSC, SEM and FTIR techniques were used to characterize the samples. Finally, the antibacterial efficiency of the knitted samples was evaluated. The experimental results revealed that the crystallinity reduction of the as-spun yarn obtained from method 1 (5%) was more than that of method 2 (3%), while the crystallinity of the modified as-spun yarns obtained with method 3 remained unchanged compared to pure yarn. However, the drawing procedure compensated for this difference. By applying methods 2 and 3, the drawing generally improved the tenacity and modulus of the modified fibers, whereas method 1 degraded the constant draw ratio. Although the biostatic efficiency of the nanocomposite yarns was excellent with all three methods, the modified fabrics obtained from methods 1 and 2 showed a higher bioactivity.

• Applied Chemistry for Engineering
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• v.16 no.4
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• pp.581-587
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• 2005

In order to obtain a highly purified p-dioxanone (PDX) as monomer of biodegradable polymer, suitable solvent must be selected. The selection was based on the solubility of impurities, and partial layer melt crystallization were carried out under the presence of solvent. The solubility of PDX in various solvents such as ethyl acetate, tetrahydrofuran, acetone, alcohols (methanol, ethanol, 1-propanol, 1-butanol and 1-pentanol) were measured over the temperature range of $-10{\sim}15^{\circ}C$. As solubility parameters, the mixing and dissolution enthalpy between the PDX and the solvents was studied based on empirical equations and the regular solution theory. The solubility and the temperature dependency of the solubility with the solvents of acetone, ethylacetate, and tetrahydrofuran of PDX were shown to have relatively high values compared to the alcohol type solvents. Also, in same alcohols, the smaller molecules and higher polarity gave higher solvency. In partial layer melt crystallization, small amount of ethylacetate selectively dissolved impurities and gave highly purified p-dioxanone, over 99.9% purity.

• Journal of Korea Foundry Society
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• v.30 no.3
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• pp.115-120
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• 2010

Recently, an advanced raw material supplying system in diecasting industry that molten metal produced by the raw material supplier can be directly delivered to the diecasting shops was proposed. It was known to have advantages of reducing melting process cost and improving working environment. However, for its successful mass production, the development of high insulation ladle is inevitable. In this study, the optimal mixing ratio of $SiO_2-Al_2O_3$ was investigated and the high insulation ladle with computer simulation result was built in a prototype and evaluated. The prototype which has refractory wall of $SiO_233%-Al_2O_3$ 35%-CaO 33% showed high insulation sufficient for carrying the Al molten metal for 138 minutes. Gas quantity result and SEM-EDS analysis on the melt poured in the ladle also showed extremely low level of 0.028 cc / 100 g and no penetration of Al molten metal into the refractory wall, satisfying the requirements for mass production.

• Polymer(Korea)
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• v.26 no.4
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• pp.462-467
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• 2002

Blends of polymethylmethacrylate (PMMA) with polyvinylidenefluoride (PVDF) were prepared by melt mixing and investigated for optical waveguide devices by using hot embossing process. The glass transition temperatures ($T_g$) of the blends were decreased with increasing PVDF contents. However, the crystalline of PMMA/PVDF blends was not appeared by DSC and XRD due to miscibility between PMMA and PVDF. Shear viscosities and refractive indices of the blends were decreased with increasing PVDF contents. Optical transmittances and absorption losses of the blends were improved with increasing PVDF contents. This is due to a decreasing of polarizability of molecules by fluorine molecule in the PVDF.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05a
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• pp.80-83
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• 2003

$SrSO_4$ were systematically added on Bi2212 from 0 to 10wt% to study the effect of Bi2212 superconductor tube characteristics. After mixing, the melted solution of Bi2212 and $SrSO_4$ was initially poured into the cylinder type of steel mold preheated at $550^{\circ}C$ for 30min and rotated at 1000rpm. Following that, tube was annealed at $840^{\circ}C$ for 72hrs. The tube dimension was 60 in diameter, 60mm in length and 2mm in thickness. XRD data suggests that there was no typical segregation phase related with $SrSO_4$. Well textured grain with typical 2212 phase was observed and average size was $20{\mu}m$. The measured critical current and critical current density of Bi2212 tube added by 5% $SrSO_4$ at 77K were 495A and $202A/cm^2$ respectively.

• Nuclear Engineering and Technology
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• v.54 no.9
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• pp.3459-3469
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• 2022

Matrix composites of n-WO₃/n-Bi₂O₃/PVA with different loadings of n-WO₃/n-Bi₂O₃ mixtures (0-15 wt%) and starch (0 and 3 wt%) were fabricated by using melt-mixing method. The X-ray attenuation capability were evaluated based on mass attenuation coefficient (μ/⍴) using a general diagnostic X-ray machine at 40-100 kVp. The effect of starch addition on the dispersion of the fillers in the PVA matrix were observed by using FESEM through morphological analysis. The fabricated samples have shrunken and caused their thickness to be decreased (0.35 mm-0.55 mm) after the drying process even though fixed thickness (2.0 mm) was set initially. The density and HVL values of the samples with 3 wt% starch was seen lower than samples without starch (0 wt%), however the former have provided improvement in filler dispersion and better X-ray attenuation capability compared to the latter. As conclusion, the matrix composite of n-WO₃/n-Bi₂O₃/PVA with 15 wt% of n-Bi₂O₃, 8 wt% of n-WO₃ and 3 wt% starch can be selected as the best promising candidate for X-ray shielding materials.

• Journal of Powder Materials
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• v.29 no.4
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• pp.314-319
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• 2022

The effect of the laser beam diameter on the microstructure and hardness of 17-4 PH stainless steel manufactured via the directed energy deposition process is investigated. The pore size and area fraction are much lower using a laser beam diameter of 1.0 mm compared with those observed using a laser beam diameter of 1.8 mm. Additionally, using a relatively larger beam diameter results in pores in the form of incomplete melting. Martensite and retained austenite are observed under both conditions. A smaller width of the weld track and overlapping area are observed in the sample fabricated with a 1.0 mm beam diameter. This difference appears to be mainly caused by the energy density based on the variation in the beam diameter. The sample prepared with a beam diameter of 1.0 mm had a higher hardness near the substrate than that prepared with a 1.8 mm beam diameter, which may be influenced by the degree of melt mixing between the 17-4 PH metal powder and carbon steel substrate.

• Polymer(Korea)
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• v.34 no.2
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• pp.144-149
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• 2010

Ag/polystyrene(PS) nanocomposites were prepared by in situ reduction of silver 2-ethylhexylcarbamate (Ag-CB) complex and follwing radical polymerization only by heating at 110 $^{\circ}C$. In contrast to this conventional heating method, the microwave irradiation afforded well-dispersed silver nanoparticles(NPs) in styrene monomer without polymerization. The synthesis of Ag NPs proceeded uniformly throughout the reaction vessel only under microwave irradiation, completing the reaction simultaneously in the whole reaction solution. Successive polymerization of the monomer containing the resultant NPs has successfully produced a hybrid of the silver NPs dispersed in PS matrix. Ag/PS (0.1/100) nanocomposites were prepared successfully by melt-mixing process using Ag/PS(4.0/100) as a master-batch. UV-VIS spectroscopy, TEM, and X-ray diffraction techniques were used to investigate the process of formation of Ag/PS nanocomposites.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.7
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• pp.450-455
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• 2015

For the practical application of a YBCO superconductor bulk, the superconductor bulk magnet with high magnetic field on a large area surface should be fabricated. To make this, YBCO single crystal bulks with fine $Y_2BaCuO_5$(Y211) particles have been prepared by the top-seed melt growth(TSMG) method with $YBa_2Cu_3O_x$, $Y_2O_3$, and $CeO_2$ mixing precursor. By using $Y_2O_3$ instead of $Y_2BaCuO_5$ as precursor, the manufacturing process became simpler and more economical. The microstructures, trapped field and critical current density of the various conditioned YBCO bulks have been observed, analyzed and measured. The different characteristic values of the several samples have been analyzed from the viewpoint of their microstructures. We have developed a $8{\times}12cm$ size superconductor bulk magnet, up to 3 T class, by using the 4 T class-high field superconducting magnetizer and confirmed the applicability of the transmission level circuit breakers by measuring the strength and speed of the superconductor bulk magnet actuator.