• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.383-386
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• 2003

In this study, the MMA-modified paste mixed waste rubber powder, which has a small elastic modulus and a large modification, was produced by using the soft unsaturated polyester resin(UP) as a binder. Then the adhesive properties according to the matrices in both underwater and air-dry conditions and the hardening shrinkage according to the contents of shrinkage reducing agent(SRA) and of MMA were surveyed. The experimental results show that, regardless of humidity of matrices the adhesive strength of polymer concrete was larger than cement concrete. the adhesive strength of MMA content of 20% was larger than MMA content of 30%. regardless of matrix materials the adhesive strength in water condition were $20{\sim}30%$ comparing with the air-dry condition. The case of MMA content of 20% showed the largest adhesive strength. In the hardening shrinkage experiment, the hardening shrinkage reduced as MMA and SRA contents increased, and the decrease of the hardening shrinkage by SRA was larger.

• Bulletin of the Korean Chemical Society
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• v.24 no.1
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• pp.37-44
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• 2003

We examined the effect of polyether-type nonionic surfactants (Brij 35, Triton X-100, Tween 20 and Tween 80) on the potentiometric properties of sodium-, potassium- and calcium-selective membranes which are prepared with widely used ionophores and four kinds of polymer matrices [poly(vinyl chloride) (PVC), polyurethane (PU), PVC/PU blend, and silicone rubber (SR)]. It was found that the PVC-based membranes, which provide the best performance among all other matrix-based membranes in the absence of nonionic surfactants, exhibited larger change in their potentiometric properties when nonionic surfactants are added to the sample solution. On the other hand, the sodium-selective SR-based membrane with calix[4]arene, potassium-selective PVC/PU- or SR-based membrane with valinomycin, and the calcium-selective SR-based membrane with ETH 1001 provide almost identical analytical performance in the presence and absence of Tween 20 or Tween 80 surfactants. The origin of nonionic surfactants effect was also investigated by interpreting the experimental results obtained with various matrices and ionophores. The results suggest that the nonionic surfactant extracted into the membrane phase unselectively form complexes with the primary and interfering ions, resulting in increased background potential and lower binding ability for the ionophore. Such effects should result in deteriorated detection limits, reduced response slopes and lower selectivity for the primary ions.

• Journal of Pharmaceutical Investigation
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• v.26 no.2
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• pp.137-144
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• 1996

The study was carried out for the preparation and evaluation of a buoyant hydrogel matrix (BHM), which is buoyant in a neutral or in pH 2.0 buffer solution, by the aspects of buoyancy, swelling, and drug release. Physical mixtures of HPC and CP in various molar ratio were employed as a mucoadhesive polymer which swells and controls the rate of drug release. Anhydrous citric acid and sodium bicarbonate in the molar ratio of 1:3 were employed as effervescing agents which provide a buoyancy for the mucoadhesive polymeric matrix. The buoyancy in vitro was expressed as both floating time$(T_{fl})$ and surfing time$(T_{sf})$, which are the time required for floating from the bottom to the surface of the medium and the time to keep the floated state at the surface of medium during release studies, respectively. A close relationship was observed between the buoyancy and the amount of effervescing agent added. $T_{fl}$ of the buoyant hydrogel matrices were decreased to about 10 seconds linearly with increasing the amount of effervescing agent in the range of 5 to 15%. $T_{sf}$ of the buoyant hydrogel matrices were varied from 1 to 3 hr depending on the amount of effervescing agent. The swelling was observed by changes in diameter of the buoyant hydrogel matrices in distilled water or acidic buffer solution, resulted in dependences on pH and the amount of effervescing agents. The release of hydrochlorothiazide from the buoyant hydrogel matrices were followed by apparent zero-order kinetics, while the buoyant hydrogel matrices were floated at the surface and maintaining their swollen shapes.

• Korea-Australia Rheology Journal
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• v.17 no.2
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• pp.41-45
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• 2005

As an effort to explore the effective use of carbon nanotubes as a reinforcing material for advanced nano-composites with polymer matrices, multi-walled carbon nanotubes (MWNTs) were successfully incorporated into polystyrene (PS) via in-situ bulk polymerization. Various experimental techniques revealed that the covalent bonds formed between PS radicals and acid-treated carbon nanotubes are favorable resulting in an effective load transfer. The enhanced storage modulus of the nanocomposites suggests a strong possibility for the potential use in industrial applications.

• Journal of Pharmaceutical Investigation
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• v.24 no.3
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• pp.139-144
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• 1994

The effect of some formulation variables on the release rate of famotidine, a $H_2$ receptor antagonist, from cellulose matrices containing hydroxypropylcellulose (HPC) in different ratios and types was investigated. The effects of tablet shape and compression pressure on dissolution rate of famotidine were studied. And the effect of the pH of dissolution media was also studied. Increase in the ratio of polymer to drug decreased the release rate of famotidine. Increase of the polymer viscosity also decreased the release rate. The release rate of famotidine was dependent on the pH of dissolution media. The release rate of drug was not much dependent on the compression pressure but dependent on the tablet shape and/or surface area. Consequently, the release rate of famotidine can be modified by changing the HPC contents, types of polymers with different viscosity grades or using appropriate fillers.

• Journal of Pharmaceutical Investigation
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• v.19 no.2
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• pp.63-69
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• 1989

Dissolution characteristics of indomethacin (IMC) from hydrophobic polymer solid dispersions were investigated. IMC-polyvinyl chloride (PVC) and IMC-ethylcellulose (EC) solid dispersions were prepared. The dissolution patterns of pure IMC, IMC-PVC and IMC-EC solid dispersions prepared at various ratios (1:1, 1:3, 1:5, 1:9 and 1:19 w/w), and those of corresponding physical mixtures were compared. It was found that the dissolution rates of IMC from solid dispersions with PVC or EC decreased in the order of 1:1>1:3>1:5>1:9>1:19 as the drug to polymer ratios decreased. Also the dissolution rates of IMC from EC solid dispersions increased according to flow rate, but PVC solid dispersions were not affected significantly. After all, PVC and EC matrices could be applied in sustained-release preparation of IMC.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.157-161
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• 2011

For the fabrication of multifunctional biopolymer nanocomposites in the combination of carbon nanotubes (CNTs), recently increasing attention has been paid to an effective homogenization of CNTs within polymer matrices and a fine tuning of the concentration. We developed an efficient method to produce homogeneous CNT-polycaprolactone nanocomposites with various and controllable CNT concentrations using an ionically-modified multi-walled CNT, MWCNT-Cl. The modified MWCNTs could be homogeneously dispersed in tetrahydrofuran (THF). Polycaprolactone (PCL) as a biodegradable and biocompatible polymer was smoothly dissolved in the homogeneous MWCNT-Cl/THF solution without agglomeration of MWCNT-Cl. The physicochemical and mechanical properties of the resultant nanocomposites were examined and the biological usefulness was briefly assessed.

• Corrosion Science and Technology
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• v.8 no.6
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• pp.223-226
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• 2009

Polymer coatings are commonly applied to metal substrates to prevent corrosion in aggressive environments such as high humidity and under salt water. Once the polymer coating has been breached, for example due to cracking or scratches, it loses its effectiveness, and corrosion can rapidly propagate across the substrate. The self-healing system we will describe prevents corrosion by healing the damage through a healing reaction triggered by the actual damage event. This self-healing coating solution can be easily applied to most substrate materials, and our dual-capsule healing system provides a general approach to be compatible with most common polymer matrices. Specifically, we expect an excellent anti-corrosion property of the self-healing coatings in damaged parts coated on galvanized metal substrates.

• Composites Research
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• v.24 no.5
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• pp.34-38
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• 2011

Carbon nanotubes (CNTs) have been widely investigated as reinforcements of CNT/polymer nanocomposites to enhance mechanical and electrical properties of polymer matrices since their discovery in the early 90's. Furthermore, the number of studies about incorporating CNTs into carbon fiber reinforced plastics (CFRP) to reinforce their polymer matrices is increasing recently. In this study, single-walled carbon nanotubes (SWNT) were dispersed in epoxy with 0.2 wt.% and 0.5 wt.%. Then, the SWNT/epoxy mixtures were processed to carbon fiber composites by a vacuum assisted resin transfer molding (VARTM) and a wet lay up method. The processed composite samples were tested for the interlaminar shear strength (ILSS). The relationship between the interlaminar shear strengths and processing, and the reinforcement mechanism of carbon nanotubes were investigated. CNT/epoxy nanocomposite specimens showed the increased tensile properties. However, the ILSS of carbon fiber composites was not enhanced by reinforcing the matrix with CNTs because of processing issues caused by increased viscosity of the matrix due to addition of CNTs particularly for a VARTM method.

• Journal of Pharmaceutical Investigation
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• v.22 no.2
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• pp.149-153
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• 1992

The applicability of sodium alginate as a carrier of 5-fluorouracil as an oral delivery system was investigated. Hydrophobicity of sodium alginate was controlled by introducing cetyl group to this polymer. The effects of degree of esterification for n-cetyl partial ester on the rate of release of 5-fluorouracil in artificial gastric juice and artificial intestinal juice were examined. The release rete of the drug in the gastric juice was mainly affected by the diffusion of the drug. The release rate of the drug in the intestinal juice could be controlled by the degree of esterification. The alginate matrices may be a valuable addition as the carrier of 5-fluorouracil for an oral delivery system.