• Korean Chemical Engineering Research
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• v.53 no.6
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• pp.703-708
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• 2015

In order to improve the dispersity of nanofiller, polyurethane (PU) nanocomposites were manufactured via poly(propylene gylcol) (PPG) dispersion with MWCNTs prepared by using a ball mill shaker. MWCNTs could be functionalized by treating with the hydrogen peroxide ($H_2O_2$). Tensile strengths and elongations at break of $PU/H_2O_2$ treated MWCNTs nanocomposites were enhanced compared to those of the PU/pristine MWCNTs nanocomposites. The good dispersion of MWCNTs shown in SEM images was obtained by the functionalization of MWCNTs surface. PU/carbon black (CB) composites showed no significant change in the tensile properties. The tensile properties of PU nanocomposites containing pristine MWCNTs or $H_2O_2$ treated MWCNTs were enhanced with increasing dispersion time. As a result, it was certified that the enhanced dispersity of nanofiller brought the improvement of the tensile properties of the MWCNTs based PU nanocomposites.

• Elastomers and Composites
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• v.49 no.4
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• pp.341-345
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• 2014

In this study, self-actuated photocatalyst that titanium dioxide doped by more than two transition metal was coated PU foam. The antibacterial and antifungal activity of self-actuated photocatalyst coated PU foam was characterized without light. The antibacterial property of self-actuated photocatalyst coated PU foam was shown to be reduced more than 96%, and the antifungal property was shown to be reduced more than 99.9%. The durability of self-actuated photocatalyst coated PU foam tested by Weather-O-meter showed the 7% reduction of formaldehyde decomposition from 96.5% before test to 89.8% after test. The observation of surface of PU foam coated with self-actuated photocatalyst showed that the catalyst was firmly attached to the surface of polyester fiber without separation.

• Analytical Science and Technology
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• v.18 no.6
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• pp.469-474
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• 2005

This paper presents a quantitative method of sequential separation of $^{90}Sr$, $^{241}Am$ and Pu radionuclides with an anion exchange resin and a Sr-Spec resin. The Pu isotopes were purified with an anion exchange resin. The americium and strontium fractions were separated from the matrix elements with an oxalate co-precipitation method. Americium fraction was separated from the strontium fraction with iron co-precipitation method and purified from lanthanides with anion exchange resin. Strontium-90 was purified from other hindrance elements with the Sr-Spec resin after oxalate co-precipitation. The measurement of Pu and Am isotopes was carried out by an ${\alpha}$-spectrometer. Strontium-90 was measured by a liquid scintillation counter. The radiochemical procedure of $^{90}Sr$, $^{241}Am$ and Pu radionuclides investigated in this study has been validated by application to IAEA-Reference soils.

• Polymer(Korea)
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• v.38 no.1
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• pp.9-15
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• 2014

Polyamide4 (PA4)-polyurethane (PU)-PA4 triblock copolymers were synthesized by isocynated (NCO)-terminated PU prepared from 4,4'-diphenyl methane diisocyante (MDI) and polytetramethylene glycol (PTMG) as an initiator and potassium pyrrolidonate (P-py) as a catalyst for anionic ring opening polymerization of 2-pyrrolidone. Subsequently copolymer was controlled to contain different or same molecular weight of PA4 hard block with same or different molecular weight of PU soft block in order to investigate the effects of those differences on various properties of triblock copolymers as a thermoplastic elastomer. As the results shown in typical properties of block copolymeric elastomers, the mechanical strength and melting point ($T_m$) of the copolymers increased with an increase in molecular weight of PA4 block while the elongation at break increased with an increase in that of PU block.

• Applied Chemistry for Engineering
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• v.4 no.3
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• pp.616-626
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• 1993

Polyurethane(PU) have an excellent flexibility and toughness so that it has been widely used as an elastomer. PMMA was blended with PU to improve the impact property. Five types of PU, having different molecular weight and different polyol types, were prepared and blended with PMMA in order to investigate the effect of molecular weight and polyol type of PU on property of PU-PMMA blend. Tensile strength of PU-PMMA blend was determined by Inston. Differential Scanning Calorymetry(DSC) and Scanning. Elctron Microscopy(SEM) were used to observe morphology change and glass transition temperature changes of PU-PMMA blends. Transparency of PU-PMMA blends was determined by haze meter. But, owing to intrinsic incompatability of PU-PMMA, Low impact strength of PMMA wasn't improved through PU-PMMA blend. therefore, polyurethane dimethacrylate(PUD), having similiar chemical structure to PU and two vinyl group at both ends, was prepared and reacted with methyl methacrylate(MMA) to form crosslinked copolymer Mechanical property of this crosslinked polymer, such as impact strength and transparency, was investigated by Instron, Izod type (Cantilever beam) impact tester and haze meter. Results of these measurements showed that crosslinked copolymer of PUD-MMA was better impact resistance than PMMA and maintained similar transparency to PMMA.

• Journal of Adhesion and Interface
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• v.7 no.1
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• pp.3-9
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• 2006

Three isocyanate groups of IP-$75^{(R)}$ and one hydroxyl group of various amino alcohols were applied for preparing cationic type water-borne polyurthane (PU) having ionic center onto flexible side chains. Average particle size, dispersion stability, viscosity, contact angle, surface energy, glass transition temperature ($T_g$), and adhesion strength of prepared water-borne PUs were measured and analyzed with different NCO/OH mol ratios, ionomers, and neutralizing agents. It was characterized that the prepared PU has a smaller particle size and a better dispersion stability than the conventional cationic water-borne PU containing ionic centers onto main chains.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.12
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• pp.5803-5819
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• 2017

In this paper, we proposed a contract theory based cooperative spectrum sharing scheme with joint power and bandwidth optimization under asymmetric information, where the primary user (PU) does not know the secondary users' (SUs) private information. To improve performance, PU needs to provide incentives to stimulate nearby SUs to help forward its signal. By using contract theory, PU and SUs' negotiations are modeled as a labor market. PU and SUs act as the employer and employees, respectively. Specifically, SUs provide labor (i.e. the relay power, which can be used for forwarding PU's signal) in exchange for the reward (i.e. the spectrum access bandwidth which can be used for transmitting their own signals). PU needs to overcome a challenge how to balance the relationship between contributions and incentives for the SUs. We study the optimal contract design which consists of relay power and spectrum access bandwidth allocation. We show that the most efficient SUs will be hired by the PU to attend the cooperative communication. PU can achieve the same maximum utility as in the symmetric information scenario. Simulation results confirm that the utility of PU is significantly enhanced with our proposed cooperative spectrum sharing scheme.

• Journal of the Korean Society of Clothing and Textiles
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• v.28 no.6
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• pp.819-829
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• 2004

This study was carried out to suggest a new swimsuit fabric with improved durability, comfort and appearance, by employing PTT(polytrimethylene terephthalate). Objective and subjective performances of newly woven PTT/PU (polyurethane) blend fabric were estimated and compared with nylon/PU(80/20) which is currently used for swimsuit. According to the questionnaire, the most serious problems of swimsuit fabrics were such that they were easily degraded by chlorinated water and this made fabric inelastic and transparent. After exposure to the chlorinated water, PTT blend fabrics showed higher retention of breaking strength, bursting strength, elastic recovery and crystallinity. suggesting that PTT/PU(87/13) was the most excellent material in durability. PTT blend fabrics absorbed less water and dried faster than nylon/PU and thus PTT/PU(87/13) was shown to be the best in respect of comfort. All of the specimens used in this study exhibited satisfactory colorfastness to sea water, chlorinated water and light except that nylon/PU(80/20) represented weak colorfastness to chlorinated water. From the subjective wearing sensation test, PTT/PU(82/18) was shown to posess the best wearing sensation. From the overall evaluation or objective and subjective properties, PTT blend fabrics exhibited superior performances to nylon/PU(80/20), suggesting that they can be successfully used as a new durable and comfortable swimsuit fabric.

• Elastomers and Composites
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• v.40 no.4
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• pp.258-265
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• 2005

To study the compressive stress, recovery force and permanent strain of foams for footwear midsole, polyurethane(PU), phylon(PH) and injection phylon(IP) foams were repetitively compressed with constant compressive stress. Maximum compressive stress of PU did not decrease with repetitive compression on the constant compressive stress, but that of IP largely decreased. Engineering strain of foams were formed by repetitively compressing the three types of foam. The engineering strain of PU was smaller than that of IP and PH. Compressive stress and recovery force of IP and PH at certain strain were decreased with repetitive compression, but that of PU was not noticeably changed.

• Journal of the Korean Society for Marine Environment & Energy
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• v.4 no.1
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• pp.3-13
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• 2001

Dissolved /sup 137/Cs, /sup 239.240/Pu, /sup 238/Pu and /sup 90/Sr contents in winter and spring of the Yellow Sea were determined to describe the distribution of artificial radionuclides. Surface water samples (100 liter) were collected by using a submerged pump, and subsurface samples (>10m depth) were collected using a 10L Niskin water sampler mounted to the Rosette sampler. The levels in the surface water ranged between 1.78～3.38 mBq kg/sup -1/ for /sup 137/Cs, 2.17～13.35 μBq kg/sup -1/ for /sup 239,240/Pu, and 1.97～3.96 mBq kg/sup -1/ for /sup 90/Sr, respectively. In particular, the concentration of /sup 239.240/Pu were 1/10 of those in the vicinity of Changjiang estuary (61～83 μBq kg/sup -1/). The difference of /sup 238.240/Pu concentration between surface and bottom water was <3.0 μBq kg/sup -1/in the Yellow Sea. It suggests that in the Yellow Sea which has shallow and high suspended sediments, /sup 239.240/Pu is preferentially removed from the water columm. The water column inventory of /sup 239.240/Pu in the Yellow Sea constitute about 0.7～0.9 % of the estimated fallout input to the area. The activity ratios of /sup 239.240/Pu//sup 137/Cs and /sup 137/Cs//sup 90/Sr ranged between 0.001～0.005, 0.79～1.65, respectively, and similar to those of open ocean which global fallout is the only source of artificial radionuclides. Therefore, it suggests that most of these artificial radionuclides in the Yellow Sea may be controlled by the atmospheric input.