• The Journal of Korean Academy of Prosthodontics
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• v.28 no.2
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• pp.91-108
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• 1990

The purpose of this study was to compare the maganitude of the discrepancies of the mounting errors in according to the states of dentitions, and to the superoinferior, anteroposterior, and rightleft driecetions. GROUP I. : Fourteen patients 22 to 26 years of age with a full complement of teeth, were used in the study. The criteria fro patient selection were a complete dentition, sparse restorarive treatment, and adequate posterior and anterior occlusan stops. And they had no sign and sympton at TMG area. GROUPII. : Eigth patients 37 to 62 years of age with bilateral free ends. The criteria for patient selection were Kennedy classification class 1 cases, and adequate posterior and anterior stops. And the opposite dentitions were a full complement of teeth. Irreversible hydrocolloid impresiion of each arch was taken of each patient. These were immediatel poured in stone and mounted on a Denar Mark II. Articulator with the arbitrary slidematic face-bow. With hand articulation th e mandibular cast was mounted to the maxillary cast in centric occlusion. Five types of interocclusal records were taken of each patient : (1) aluwax (2) baseplate wax; (3) znic oxide-eugenol pasts; (4) polyether (Ramitec); (5) modeling compound. All measurement of the five selected recording materials were compared with those of the hand-articulated full arch models in centric occlusion or maximum interdigitation. The results were as follows; 1. There were statistical differences in amount of devitation in according to the materials and the states of dentition. The amount of deviation of compound was the largest. 2. There were statistical differences in amount of deviation in complete dentition at all directions. The amount of diviation of compound was the largest. And at the right-left direction the amount of znic oxide-eugenol paste was larger than that of baseplate wax. 3. There was a statistical difference in amount of diviations in partial edentulous dentition at the superoinferior direction. The amount of deviation of compound was larger than that of znic oxide-eugenol paste. 4. There was as statistical difference in amount of deviations in partial edentulous dentition at the right-left direction. The amount of deviation of baseplate wax was larger that tnat of polyether. 5. There was not a statistical difference in amount of diviation in partial edentulous dentition at the anteroposterior direction.

• Polymer(Korea)
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• v.26 no.2
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• pp.218-226
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• 2002

For the preparation of high resilience polyurethane (PU) foams with polyether type cell openers which have different ethylene oxide (EO) content, molecular weight and chain structure, the influences of tell opener structure on the kinetics, rheology, structural stability, open cell content and mechanical properties of the obtained foam were investigated. It was observed that urea formation reaction was delayed with the increase of EO content and incorporation of ester linkage in cell opener molecule and was relatively independent on the molecular weight. With the rheological studies, the decreases of viscosity and storage modulus were confirmed for the increase of EO content and molecular weight, so that the resulted foam had low structural stability and high open cell content. The cell opener having ester linkage in molecule exhibited the lowest values of viscosity and storage modulus and the obtained foam has high open cell content. However, the structural stability increased due to the larger intermolecular interaction of ester linkage. The hardness, tensile strength, tear strength and elongation of foam were deteriorated with increase of EO content and molecular weight of tell opener. On the other hand, the cell opener having ester linkage in molecule improved the values of tensile strength, tear strength and elongation.

• Membrane Journal
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• v.28 no.4
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• pp.265-270
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• 2018

In previous studies, a poly(ethylene oxide)(PEO)/Ag nanoparicles (AgNPs)(precursor $AgBF_4$)/p-benzoquinone (p-BQ) composite membrane was prepared for olefin/paraffin separation and the performance of this composite membrane was maintained at a selectivity of 10 and a permeability of 15 GPU. However, since the price of $AgBF_4$ precursor is high, this study used $AgNO_3$ as a precursor of Ag nanoparticles which is competitive in terms of price. As a result, it was observed that the separation performance was not obtained because the existing $NO_3{^-}$ could surround AgNPs. In this study, we fabricated PEO, poly(vinyl alcohol)(PVA), and polyether block amide-1657 (PEBAX-1657) polymer composite membrane using electron acceptor 7,7,8,8-tetracyanoquinodimethane (TCNQ) for separation performance even when $AgNO_3$ was used as a precursor of Ag nanoparticles. As a result, it was analyzed that the performance was not observed regardless of the influence of the polymer and the electron acceptor, indicating that the anion of the precursor plays a crucial role in the separation performance.

• Membrane Journal
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• v.22 no.3
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• pp.201-207
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• 2012

In this study, we investigated permeation of single gas ($N_2$, $O_2$, $CF_4$, and $SF_6$) through flat sheet membrane composed of PDMS (poly-dimethylsiloxane) and PEBAX (polyether block amides). Gas permeation experiment was performed with various feed pressure. Permeability was estimated using permeation flux measured by continuous-flow technique. The permeability of gases except $SF_6$ in PDMS were decreased with the upstream pressure increased. $SF_6$ is much more permeable than $CF_4$, which is due to higher critical temperature of $SF_6$. The permeability decreased in the following order: $O_2$ > $N_2$ > $SF_6$ > $CF_4$. On the other hand, the permeability of gases in PEBAX followed the order: $O_2$ > $N_2$ > $CF_4$ > $SF_6$ which are opposite of the order of kinematic diameter (${\AA}$)($SF_6$ > $CF_4$ > $N_2$ > $O_2$). The $SF_6/CF_4$ pure gas selectivity in PDMS was 2.1 at 0.7 MPa.

• Korean Chemical Engineering Research
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• v.49 no.4
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• pp.460-464
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• 2011

Poly(ether-block-amide)(PEBA, $PEBAX^{TM}$) resin is a thermoplastic elastomer combining linear chains of hard-rigid polyamide block interspaced soft-flexible polyether block. It was believed that the hard polyamide block provides the mechanical strength and permeation selectivity, whereas gas transport occurs primarily through the soft polyether block. The objective of this work was to investigate the gas permeation properties of carbon dioxide and methane for $PEBAX^{TM}$-1657 membrane and compare with those obtained for other grade of $PEBAX^{TM}$, $PEBAX^{TM}$-2533. And the organic/inorganic hybrid membranes were prepared using $PEBAX^{TM}$ and TEOS(tetraethoxysilane) by sol-gel process, and gas permeation properties were studied. $PEBAX^{TM}$-2533 membrane exhibited higher gas permeability coefficients than $PEBAX^{TM}$-1657 membrane. This was explained by the increase of chain mobility. The permeability coefficients for $PEBAX^{TM}$/TEOS hybrid membranes were higher than pure $PEBAX^{TM}$ membranes. This results were explained by the reduction of crystallinity of polyamide block by the introduction of TEOS. Ideal separation factor of hybrid membranes does not change much. This might be due to the increase of solubility selectivity.

• Fibers and Polymers
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• v.4 no.2
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• pp.89-96
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• 2003

A vertebral cage is a hollow medical device which is used in spine forgery. By implanting the cage into the spine column, it is possible to restore disc and relieve pressure on the nerve roots. Most cages have been made of titanium alloys but they detract the biocompatibility. Currently PEEK (polyether ether ketone) if applied to various implants because it has good properties like heat resistance, chemical resistance, strength, and especially biocompatibility. A new shape of vertebral cage is designed and injection molding of PEEK is considered for production. Before injection molding of the cage, it is needed to evaluate process conditions and properties of the final product. Variables affecting the shrinkage of the cage are considered, e.g., injection time, packing pressure, mold temperature, and melt temperature. By using the numerical simula-tion program, MOLDFLOW, several cases are studied. Data files obtained by MOLDFLOW analysis are used for stress anal-ysis with ABAQUS, and shrinkage and residual stress fields are predicted. With these results, optimum process conditions are determined.

• The Journal of Korean Academy of Prosthodontics
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• v.31 no.1
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• pp.77-86
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• 1993

The purpose of this study was to compare the sagittal condylar guidance obtained by the graphic method(pantographic tracing) with that produced by the positional method(check-bite). Ten adults who had normal occlusion and were free of TMJ dysfunction were selected, and the clutches were constructed. At first pantographic survey was performed and the articulator was adjusted with each pantographic recording. And then three protrusive check-bite were taken on the subjects using the polyether$(Lamitec^{(R)})$ on the buccal side of the posterior teeth without the interocclusal record method and the vericheck method was performed with each protrusive check-bite. Sagittal condylar guidances obtained by using the pantograph and Vericheck were compared and analyzed statistically. The results were as follows: 1. The average condylar guidance ankle at 4mm and 7mm from centric relation point on the pantograph $(35.9{\pm}1.10^{\circ},\;32.4{\pm}1.55^{\circ})$ was statisccally significant(P<0.01). 2. The average condylar guidance angle of the Vericheck was $27.0{\pm}3.43^{\circ}$. 3. The comparison of the right and left was not statistically significant in all group(P>0.05). 4. The comparison of pantograph and Vericheck was statistically significant in the right and left(P<0.001).

• Applied Chemistry for Engineering
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• v.16 no.1
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• pp.39-44
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• 2005

In this study, polyurethane-acryl emulsion resins were synthesized from HDI (hexamethylene diisocyanate), IPDI (isophorone diisocyanate), Polyol, 2-HEMA (2-hydroxy ethylmethacrylate), n-BA (n-butyl acrylate) and MMA (methylmethacrylate). The effects of polyol types on the properties of polyurethane-acryl emulsion resin, such as degree of strength and water resistance and on the manufacturing process were investigated. In addition, the results were compared with those of acrylic emulsion. The test results showed that polyester type polyol demonstrated stronger tensile strength and higher water resistance with time than did acrylic emulsion and polyether type polyol.

• Archives of Pharmacal Research
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• v.20 no.4
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• pp.372-374
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• 1997

In order to develop new anti-inflammatory agents having different action mechanisms compared with nonsteroidal and steroidal anti-inflammatory drugs, the culture broths of various actinomycetes isolated from soil were screened using an in vivo mouse ear edma assay and one strain (Streptomyces sp. MT 2705-4: KCTC 8651 P) was selected. Activity-guided purification led to the isolation of a polyether compound, dianemycin. Topically, dianemycin showed a potent anti-inflammatory activity in mouse ear edema induced by croton-oil or arachidonic acid.$ED_{50}$value of dianemycin was found to be 0.8 mg,/ear compared to 0.4 mg/ear of prednisolone in croton-oil ear edema. However, dianemycin did not show the inhibitory activity in UV-erythema and delayed hypersensitivity reaction. These results indicate that dianemycin is a potential topical anti-inflammatory agent.

• Polymer(Korea)
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• v.25 no.3
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• pp.385-390
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• 2001

The A-B-A type block copoly(ester-ether)s consisting of poly(L-lactic acid) (PLLA)(A) and poly(oxyethylene-co-oxypropylene)(B) were prepared to improve the mechanical properties and hydrolyzability of PLLA. The block copolymers showed an improved flexibility due to the incorporation of the soft segments. Then, the same copolymer has an improved anti-thrombogenicity probably due to the specific microphase separation structure in the surface. The AFM of the film of the block copolymer revealed that the surface was quite flat in comparison with that of PLLA. Therefore, the flatness of the surface may be related with the increased anti-thrombogenicity of the copolymer film.