• Transactions on Electrical and Electronic Materials
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• v.14 no.1
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• pp.1-8
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• 2013

The present approach shows the use of nano-silica/nano-alumina in polyurethane (PU) matrix, which lead to significant improvements in the mechanical and thermal properties of the nano-composite. It is observed that with incorporation of 1% of nano-alumina into the PU matrix, there is an improvement in the tensile strength of around 50%, and for nano-silica the improvement is around 41%, at the same concentration. The morphological data shows that above 3% of the nano particles there are agglomerations in the nanocomposite. Again with the absorption of moisture, there is a decrease in the thermal and mechanical properties of the PU resin, but in this research work it is observed that with the incorporation of the nano particles, in the presence of absorbed moisture there is an improvement in mechanical and thermal properties of the composite, over that of the PU matrix.

• Journal of Biomedical Engineering Research
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• v.16 no.1
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• pp.1-8
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• 1995

A variety of experiments of endothelial cell seeding onto artificial vessels have been performed. To improve endothelialization, one or two components of the extracellular matrix (ECM) have been used as an underlying matrix. In this study, the whole ECM excreted from fibroblasts was used as an underlying matrix. Fetal human fibroblasts were cultured on a polyurethane (PU) sheet. After a conflu; ence was attained, the cytoskeleton and the nuclei of the fibroblast were destroyed using Triton-X. Mitomycin, or irradiation. Omental microvascular endothelial cells from adult human were seeded onto various substrates. After 12 days in culture, the cells were counted. It was observed that the ECM treated by irradiation had the highest cell number. In addition, the cells on this substrate exhibited the most typical endothelial cell morphology. For preliminary animal experiments the PU vessels (inner diameter, 1.5mm) coated with ECM were implanted in the infrarena] abdominal aorta of rat. After the vessels had been implanted for 5 weeks, it was found that the surface of the PU vessels was completely covered with endothelia] cells. In conclusion, we can state that the fibroblast-derived whole ECM makes a better underlying substrate for the endothelialization of small diameter artificial vessels.

• Composites Research
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• v.24 no.3
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• pp.39-45
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• 2011

Adhesive joints are widely used for structural joining applications in various fields and environmental conditions. Polyurethane (PU) and Epoxy adhesives are now being used for liquefied natural gas (LNG) carriers at cryogenic temperatures. This paper presents a comprehensive evaluation of epoxy and PU adhesive bonds between Triplex sheets at normal and cryogenic temperatures. The most significant result of this study is that for all adhesives tested, there is a significant decrease in peel strength at cryogenic temperatures. However, the reasons for the decrease in peel strength for epoxy and PU adhesives differ. Consequently, PU adhesives can be considered better suited for use in applications requiring high bonding performance at cryogenic conditions, such as in LNG carriers.

• Tribology and Lubricants
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• v.28 no.6
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• pp.333-339
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• 2012

Typical magneto-rheological (MR) elastomers consist of silicon-based material. A number of studies have been carried out to evaluate the vibration and tribological characteristics of silicon-based MR e-lastomers. However, these elastomers have quite low strength, so they have low wear resistance. In this study, polyurethane-based MR elastomers with performances better than those of MR elastomers. Experiments have been conducted on different MR elastomers (Pu MR elastomer, Pu-Si MR elastomer, and Pu-wrapped-Si MR elastomer) and different predefined magnetic directions (Non-Direction, Vertical Direction, and Horizontal Directionality) to evaluate the friction and wear performance under a magnetic field. The results show that Pu-wrapped-Si MR elastomer with a horizontal predefined magnetic field has the best performance in terms of wear.

• Applied Chemistry for Engineering
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• v.9 no.5
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• pp.648-653
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• 1998

This study examines the effects of cell size and structure on the oil adsorption by polyurethane (PU) foam. A series of oil-adsorptive PU foam has been prepared, using various molecular weight of polyether polyol (GP-1000, GP-3000, GP-4000, GP-5000), together with TDI-80, water and additives. It was found that the cell size of PU foam decreased with increasing the agitation speed and surfactant content. Oil-adsotption of PU foam increased over 2000% with the increase of molecular weight of polyol and with the decrease of cell size. Increase in the surfactant content and the viscosity of adsorbed oil also give a remarkable decrease in oil adsorption.

• Composites Research
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• v.29 no.4
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• pp.161-166
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• 2016

Carbon nanotube buckypaper (CNTs-BP)/thermoplastic polyurethane (PU) elastomer composites were successfully fabricated. The CNTs-BP/PU nanocomposites exhibited simultaneous improvements in both tensile modulus and strength by 1360 and 430%, respectively, as compared to pure PU. Possible reinforcing mechanisms were evidenced by SEM analyses and tensile tests. The CNTs-BP/PU nanocomposites can be potentially used as an inter-reinforcing agent in ultra-lightweight, high-strength aircraft, carbon-fiber-reinforced plastics, etc.

• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.350-351
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• 2003

Polyurethane은 물리적, 화학적 성질이 매우 다른 두 segment(hard/soft)로 이루어진 block copolymer로서 hard segment의 화학적 구조가 hard segment의 packing정도에 영향을 미쳐, PU의 미세상분리 현상을 결정하며 결과적으로 PU의 물리적 성질에 큰 영향을 미치게 된다$^1$. 본 연구에서는 hard segment의 packing을 향상시켜 PU은 열적 기계적 특성을 향상시키기 위하여 방향족환으로 구성되어 있어 aromatic diol의 일종인 hydroxyquinone-di-(beta-hydroxyl)ether(HQEE)를 chain extender로 사용하여 PU를 합성하였다. (중략)

• Elastomers and Composites
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• v.50 no.1
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• pp.35-48
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• 2015

Polyhedral oligomeric silsesquioxane (POSS) is an important inorganic-organic hybrid material with a three-dimensional structure. Polyurethane (PU) is a widely applied polymer that has versatile properties with the change of two phase structure. When POSS is incorporated into PU by physical or chemical methods, many properties can be greatly improved, such as mechanical properties, thermal stability, biodegradation resistance, and water resistance. This paper reviews the recent progress in preparation, structure, and performance of POSS-modified polyurethane from the viewpoint of physical blending and chemical modification.

• Polymer(Korea)
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• v.25 no.3
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• pp.391-398
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• 2001

Two-component polyurethane (PU) flame-retardant coatings were prepared by blending tribromo modified polyesters ($TBAO_s$) and isocyanate.$TBAO_s$ were synthesized by condensation polymerization of tribromoacetic acid, a flame-retardant component, with 1,4-butanediol, adipic acid, and trimethylolpropane. The content of tribromoacetic acid was varied by 10, 20, and 30 wt% for the reaction. Various physical properties of these new flame-retardant coatings were comparable to nonflame-retardant coatings. Coatings with 20 wt% tribromoacetic acid did not burn during the vertical burning test.

• Textile Coloration and Finishing
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• v.22 no.3
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• pp.246-256
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• 2010

This study studies on the physical property of MWNT/PU composite film for electrostatic dissipation (ESD) function by dispersing multi-wall carbon nanotubes (MWNT) in dimethylformamide (DMF) and by combining it with polyurethane(PU). For this purpose, four kinds of MWNT were selected and the composite films were made by dispersion processing, and their physical properties were measured and investigated in terms of electrical conductivity. For dispersion parameters, four MWNT contents(0.5, 1, 2, 5wt%) and two dispersion times(30min, 120min) were selected. The dispersion property and the electrical conductivity of MWNT/PU film was measured using a UV-Vis spectrometer and conductivity measuring apparatus. Finally, their physical properties according to the dispersion conditions were analyzed and discussed with various processing conditions.