共查询到20条相似文献,搜索用时 15 毫秒
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Elchueva A. D. Aristova N. V. Bortnikov I. V. Tabachkov A. A. 《Russian Journal of Applied Chemistry》2001,74(5):860-863
Single-component urethane sealing formulations with aldimines as cross-linking agents were developed. The temperature dependence of the curing time of the sealants was examined. The influence of the -CH = N-/-NCO ratio and of fillers (industrial carbon and chalk) on their physicochemical properties was studied. 相似文献
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Strel’nikov V. N. Senichev V. Yu. Slobodinyuk A. I. Savchuk A. V. Volkova E. R. Makarova M. A. Belov Yu. L. Derzhavinskaya L. F. Selivanova D. G. 《Russian Journal of Applied Chemistry》2018,91(12):1937-1944
A procedure was suggested for preparing epoxy ether urethane oligomers via intermediate oligodiisocyanates with increased content of the starting 2,4-toluene diisocyanate. The procedure allows preparation of epoxy-containing oligomers with appreciable fraction of low-molecular-mass diglycidyl urethane. The presence of diglycidyl urethane in the binder enhances not only the adhesion but also the strength of the cured material without significantly affecting the glass transition point of the binder. Elastic materials prepared by curing the compounds studied with cylcoaliphatic amines exhibit enhanced levels of strength and low-temperature elasticity.
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Processes of vulcanization and adhesion of polysulfide sealants are reviewed and vulcanizing agents constituting polysulfide sealants are described. 相似文献
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Valuev V. I. Mikhailova L. N. Okhotnikov M. A. Dal'gren I. V. 《Russian Journal of Applied Chemistry》2004,77(5):835-837
Polycondensation of bifunctional hydroxyl-containing oligodienes with diisocyanates was studied by gel permeation chromatography, IR spectroscopy, and rheokinetic method. The kinetics of oligodiene urethane formation and the properties of the resulting oligomers, including the molecular-weight distribution and viscosity, were studied in relation to the ratio of the isocyanate and hydroxy groups. 相似文献
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Natalie Artzi Tarek Shazly Cristina Crespo Adriana Bon Ramos H. Keith Chenault Elazer R. Edelman 《Macromolecular bioscience》2009,9(8):754-765
Swellable PEG amine/dextran aldehyde composite materials are emerging as a controlled, biocompatible tissue adhesive. We explain how preservation of natural tissue amines provides biocompatibility for PEG/dextran that exceeds the stringent, destructive cyanide‐based chemistry of cyanoacrylates, and adhere far better than fibrin glue. Strategic variations of material composition allow for the improvement of biocompatibility and adhesion strength. Material variations can be tailored to match the needs of specific tissue beds for an array of clinical applications. PEG/dextran cohesive properties are most responsive to variations in the PEG component (number of arms and solid content), while tissue/material adhesion strength is primarily determined by the number of aldehydes in the dextran.
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The possibility of shortening the curing time of glue sealants based on silanized polyetherethanes has been studied. It is shown that fast-curing sealants with high physicomechanical characteristics can be obtained using the domestic commercially available SM-18 binder blended with a synthesized prepolymer based on oligoethers and diisocyanates. 相似文献
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H. S. Eleuterio 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(6):1027-1052
Abstract Epoxidation of perfluoroolefins to perfluoroepoxides has made a new class of monomers available. Perfluoroepoxides undergo facile ring-opening reactions with nucleophiles which under the proper reaction conditions can lead either to poly-perfluoroethers or to other classes of fluorocarbons previously unavailable or available with great difficulty. The preparation of perfluoroepoxides is described. 相似文献
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McKiernan M Huck J Fehrentz JA Roumestant ML Viallefont P Martinez J 《The Journal of organic chemistry》2001,66(20):6541-6544
A general method has been developed for the synthesis of N-tert-butyloxycarbonyl N-carboxyanhydrides from beta-amino acids using Vilsmeier complex. These beta-UNCA are stable, and the reactivity with different nucleophiles (alcohol, amine, lithium enolate) was studied. 相似文献
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Mattia Riccardo Monaco Dr. Sébastien Prévost Prof. Dr. Benjamin List 《Angewandte Chemie (International ed. in English)》2014,53(31):8142-8145
The hydrolytic ring opening of epoxides is an important biosynthetic transformation and is also applied industrially. We report the first organocatalytic variant of this reaction, exploiting our recently discovered activation of carboxylic acids with chiral phosphoric acids via heterodimerization. The methodology mimics the enzymatic mechanism, which involves an enzyme‐bound carboxylate nucleophile. A newly designed phosphoric acid catalyst displays high stereocontrol in the desymmetrization of meso‐epoxides. The methodology shows wide generality with cyclic, acylic, aromatic, and aliphatic substrates. We also apply our method in the first highly enantioselective anti‐dihydroxylation of simple olefins. 相似文献
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James V. Crivello 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(8):591-598
The effects of temperature on the photoinitiated cationic ring‐opening polymerizations of a number of different epoxide monomers were studied with the aid of a modified optical pyrometer instrument. Depending on the structures of the epoxide monomer, various behaviors were observed. The results were interpreted as due to steric and electronic features inherent in the structures of the monomers that affect the stabilization of the secondary oxonium ions, which are formed as intermediates in these polymerizations. At one extreme, cycloaliphatic epoxides such as cyclohexene oxide give highly reactive oxonium intermediates that exhibit high rates of polymerization even at subambient temperatures. At the other extreme, alkyl glycidyl ethers produce oxonium ion intermediates, which are so stable that they do not spontaneously react to form polymer at room temperature. By manipulation of the structure of the epoxide monomer, novel monomers with tailored reactivities can be prepared. 相似文献
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Dr. Youwei Ma Prof. Dr. Xuesong Jiang Prof. Dr. Zixing Shi Dr. José Augusto Berrocal Prof. Dr. Christoph Weder 《Angewandte Chemie (International ed. in English)》2023,62(36):e202306188
Devising energy-efficient strategies for the depolymerization of plastics and the recovery of their structural components in high yield and purity is key to a circular plastics economy. Here, we report a case study in which we demonstrate that vinylogous urethane ( VU ) vitrimers synthesized from bis-polyethylene glycol acetoacetates ( aPEG ) and tris(2-aminoethyl)amine can be degraded by water at moderate temperature with almost quantitative recovery (≈98 %) of aPEG . The rate of depolymerization can be controlled by the temperature, amount of water, molecular weight of aPEG , and composition of the starting material. These last two parameters also allow one to tailor the mechanical properties of the final materials, and this was used to access soft, tough, and brittle vitrimers, respectively. The straightforward preparation and depolymerization of the aPEG -based VU vitrimers are interesting elements for the design of polymer materials with enhanced closed-loop recycling characteristics. 相似文献
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光固化氨酯改性丙烯酸系水性涂料 总被引:15,自引:0,他引:15
以丙烯酸丁酯,苯乙烯,丙烯酸及甲基丙烯酸-β-羟乙酯共聚合成了具有羟基和羧基侧基的丙烯酸共聚物,再用甲苯二异氰酸酯与甲基丙烯酸-β-羟乙酯的半加成物对上述丙烯酸树脂进行接枝改性,经胺中和后,水性化,可得较为稳定的自乳化光敏树脂水分散体系。 相似文献
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A. V. Savenkova 《Polymer Science Series D》2008,1(3):185-187
Problems relevant to the development of new, and improvement of available, organosilicon sealants are set forth. Newly elaborated materials, which, in addition to enhanced heat and cold resistance, exhibit a number of other valuable properties and technological advantages, are described. 相似文献