• Journal of Adhesion and Interface
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• v.9 no.2
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• pp.8-15
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• 2008

Microcapsules have been widely used in cosmetics and pharmacology as controlled delivery devices of various active materials. Chitosan is the second most plentiful natural biopolymer with biocompatibility and nontoxicity. The chitosan microcapsules were prepared by the water-in-oil (W/O) emulsion method using glutaraldehyde as a crosslinking agent. Span80 was used as an emulsifier, and mineral oil was used as a medium material. Perfectly spherical microcapsules were obtained in the size range of $2{\sim}10{\mu}m$. The effects of emulsifier concentration and stirring speed on the average particle size and distribution were investigated. Encapsulation and release behavior of the microcapsules with different amount of the crosslinking agent (glutaraldehyde), different chitosan contents and different emulsifier concentration conditions were also investigated. The release rate of riboflavin was controlled by the crosslinking density of the chitosan and amount of emulsifier in the preparation of the microcapsule.

• Journal of Adhesion and Interface
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• v.14 no.4
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• pp.175-182
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• 2013

In this work, we aim to investigate the specific gravity, thermal, and mechanical property changes of solid-state extruded polypropylene (PP)/calcium carbonate composites before and after orientation. For this work, we prepared $PP/CaCO_3$ composites having two different sizes (OM-1 and OM-10). On increasing the filler content, the specific gravity of the composites increases. The specific gravity of the oriented specimen containing filler in PP matrix is found to be much smaller than that of pre-specimen due to the formation of more microvoids. The presence of microvoids in case of oriented composite specimen significantly affected the tensile and flexural properties of the composites. It was observed that the effect of orientation on both flexural strength and modulus is much stronger than the effect of filler contents, regardless of the filler particle size.

• Polymer(Korea)
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• v.37 no.2
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• pp.162-166
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• 2013

Graphene-coated polymer particles have attracted research interests due to their emerging applications derived from their controlled structure and morphology. To control the properties of graphene oxide (GO)-polystyrene (PS) composite particles, the adsorption time and instantaneous adsorption conditions were investigated by varying their mixing method. Polystyrene particles prepared by emulsion polymerization were modified to have positive surface charge by adsorption of polyethylene imine (PEI) on the surface of PS particles. GO prepared by the chemical exfoliation method had negative surface charge from the oxygenated groups. The adsorption of the negatively charged GOs onto the positively charged PS particles was successfully completed, and it was found that a longer adsorption time and a greater difference in the instantaneous relative concentration led PS-GO particles to have more homogeneously coated surfaces without aggregation.

• Journal of Adhesion and Interface
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• v.14 no.2
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• pp.82-87
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• 2013

Preliminary studies on the synthesis of magnetic nanoparticles including nanoporous carbon materials have been done via a direct carbonization process from resol, ferric nitrate and triblock copolymer F127. The results show that the nanoporous magnetite/carbon ($Fe_3O_4$/carbon) with a low $Fe_3O_4$ content (1 wt%) possesses an ordered 2-D hexagonal (p6mm) structure, uniform nanopores (3.6 nm), high surface areas (up to 635 $m^2/g$) and pore volumes (up to 0.48 $cm^3/g$). Magnetite nanoparticles with a small particle size (10.2 nm) were confined in the matrix of amorphous carbon frameworks with superparamagnetic property (7.7 emu/g). The nanoporous magnetite/carbon showed maximum adsorption amount (995 mg/g) of ibuprofen after 24 h at room temperature. The nanoporous magnetite/carbon was separated from solution easily by using a magnet. The nanoporous magnetite/carbon material is a good adsorbent for hydrophobic organic drug molecules, i.e. ibuprofen.

• Journal of Adhesion and Interface
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• v.22 no.4
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• pp.128-135
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• 2021

In this study, the acid polyols containing acid groups were synthesized, the novel polyurethane adhesive was developed by introducing the acid polyol by content. The acid polyols were introduced, the mechanical properties showed the maximum value when the acid content was 0.1 to 0.3 wt%, and it was confirmed that the mechanical properties and adhesive strength decreased at the content higher than 0.5 wt%. As the acid group, carboxylic acid and sulfuric acid were introduced to compare properties, and carboxylic acid showed stronger hydrogen bonding potential than sulfuric acid and improved mechanical properties. In addition, the correlation between particle size and mechanical properties was confirmed by introducing ZnO and CaCO₃. When ZnO and CaCO₃ were introduced, an ionic bond was formed with an acid group, and it was confirmed that mechanical properties were increased.

• Journal of the Korean Wood Science and Technology
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• v.34 no.5
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• pp.42-51
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• 2006

The this study, the effect of rice husk flour (RHF) as scavenger on formaldehyde emission rate and formaldehyde content from urea-formaldehyde (UF) resin bonded RHF content wood particleboards (PB). Two type of particle size ($30{\mu}m$ and $300{\mu}m$) of RHF was premixed with the UF resin at 5% and 15% by weight. The performance of UF resins is greatly influenced by the curing characteristics in their curing processing. The curing behavior was monitored activation energy ($E_a$) by DSC and pH variation according to RHF contents. PB with dimensions of $27cm{\times}27cm{\times}0.7cm$ was prepared at a specific gravity of 0.75 using $E_1$ and $E_2$ class UF resins. Formaldehyde emission and formaldehyde content from RHF filled PB bonded with UF resin was measured by 24 h desiccator and perforator method, respectively. RHF causes an increased pH of UF resin. $E_a$ of the modified UF resin decreased independently of RHF particle size. As the pH and the $E_a$ variation of the UF resin containing RHF increased, the amount of formaldehyde content decreased. The formaldehyde emission and formaldehyde content levels of the PB bonded with 15 wt% of $30{\mu}m$ RHF and $E_2$ type UF resin were low and satisfied grade $E_1$, as measured by 24 h desiccator and perforator method. The result of a comparison between 24 h desiccator and perforator test using PB showed that the linear regression analyses show a good correlation between the results for the 24 h desiccator and the perforator tests. The linear regression of a correlation between the desiccator and the perforator was Y=4.842X-0.064 ($R^2=0.989$). RHF was effective at reducing formaldehyde emission and formaldehyde content in urea-formaldehyde adhesives when used as scavenger.

• Polymer(Korea)
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• v.32 no.2
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• pp.109-115
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• 2008

Because demineralized bone particle (DBP) contains various bioactive molecules such as cytokines, it is widely used biomaterials in the field of tissue engineering. In this study, we investigated the effect of 2-dimensional DBP/PLGA hybrid films on adhesion, proliferation and phenotype maintenance of intervertebral disc cells. PLGA films incorporated with different amount (0, 10, 20, 40 and 80 wt%) of DBP were prepared by the solvent evaporation method and characterized by scanning election microscopy (SEM). PLGA film has a flat and smooth surface. According to the increase of content of DBP, the surface of DBP/PLGA film exhibited few agglomerates and increased the roughness of the surface. Annulus fibrosus (AF) and nucleus pulposus (NP) cells were cultured on PLGA and DBP/PLGA film surface, and then examined the cell adhesion and proliferation by the cell count and SEM observation. The result of cell count and SEM observation revealed that 10 and 20% DBP in DBP/PLGA films were superior to adhesion and proliferation of both AF and NP cells. We confirmed that specific gene expression of disc cells on DBP/PLGA film based on the cell count result. Disc cells seeded on 20% DBP/PLGA film expressed the gene of type I and II collagen continuously. Therefore, pertinent content of biomaterials could provide more appropriate condition on adhesion and proliferation of cell. And this results may be used as a basic data for the intervertebral disc regeneration using tissue engineering.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.2
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• pp.141-149
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• 2015

In the fabrication of electronic circuits used in electronic products, molybdenum thin films are deposited on semiconductors to prevent oxidation. During the deposition, the presence of a particle or dust at the interface between the thin film and substrate causes the decrease of adhesion, performance, and life cycle. In this study, a damage measurement targeting two kinds of glass substrate, with and without particles, was performed in order to measure the change in the molybdenum thin film deposition area in the presence of a particle. Clean and dirty molybdenum thin film specimens were fabricated and directly deposited on a substrate using the sputtering method, and a reflection-type digital holographic interferometer was configured for measuring the damage. Reflection-type digital holography has several advantages; e.g., the configuration of the interferometer is simple, the measurement range can be varied depending on the magnification of a microscopic lens, and the measuring time is short. The results confirm that reflection-type digital holography is useful for the measurement of the damage and defects of thin films.

• Journal of the Korean institute of surface engineering
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• v.46 no.4
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• pp.145-152
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• 2013

The growth behavior of nanocrystalline diamond (NCD) film has been studied for three different substrates, i.e. bare Si wafer, 1 ${\mu}m$ thick W and Ti films deposited on Si wafer by DC sputter. The surface roughness values of the substrates measured by AFM were Si < W < Ti. After ultrasonic seeding treatment using nanometer sized diamond powder, surface roughness remained as Si < W < Ti. The contact angles of the substrates were Si ($56^{\circ}$) > W ($31^{\circ}$) > Ti ($0^{\circ}$). During deposition in the microwave plasma CVD system, NCD particles were formed and evolved to film. For the first 0.5h, the values of NCD particle density were measured as Si < W < Ti. Since the energy barrier for heterogeneous nucleation is proportional to the contact angle of the substrate, the initial nucleus or particle densities are believed to be Si < W < Ti. Meanwhile, the NCD growth rate up to 2 h was W > Si > Ti. In the case of W substrate, NCD particles were coalesced and evolved to the film in the short time of 0.5 h, which could be attributed to the fact that the diffusion of carbon species on W substrate was fast. The slower diffusion of carbon on Si substrate is believed to be the reason for slower film growth than on W substrate. The surface of Ti substrate was observed as a vertically aligned needle shape. The NCD particle formed on the top of a Ti needle should be coalesced with the particle on the nearby needle by carbon diffusion. In this case, the diffusion length is longer than that of Si or W substrate which shows a relatively flat surface. This results in a slow growth rate of NCD on Ti substrate. As deposition time is prolonged, NCD particles grow with carbon species attached from the plasma and coalesce with nearby particles, leaving many voids in NCD/Ti interface. The low adhesion of NCD films on Ti substrate is related to the void structure of NCD/Ti interface.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.1
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• pp.1-7
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• 2017

As a part of studies to lower the infrared (IR) emissivity from the surface of exhaust nozzle in the turbo jet engine, stainless steel plate was coated with copper particle/meta-aramid resin composites and the IR emissivity of the plate were investigated. Binders of filler particles based on synthetic polymers generally undergo thermal decomposition before $300^{\circ}C$. It was found that the meta aramid resin was thermally stable after the test at $320^{\circ}C$, confirming the excellent thermal stability. Contents of copper particles in the composites were varied from 0 to 70% by volume. It was observed that the copper particle/meta aramid resin composites showed good adhesion after the tests at $320^{\circ}C$. The specimen coated with the composite containing 50 vol% of copper particles showed the lowest IR emissivity, 0.6, at $320^{\circ}C$.