Journal articles: 'Polyurethane reaction'

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Schmidt and Eschig. "Hydrophobilization of Furan-Containing Polyurethanes via Diels–Alder Reaction with Fatty Maleimides." Polymers 11, no. 8 (July 31, 2019): 1274. http://dx.doi.org/10.3390/polym11081274.

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We describe new hydrophobic functionalized linear polyurethane resins by combining N-alkyl maleimides via the Diels–Alder reaction with linear furan-modified polyurethanes. This procedure provides the opportunity for the post-polymerization-functionalizing of polyurethanes. Access to furan-bearing polyurethanes is achieved via the reaction of a furan-containing diol, polyethylenglycol (PEG), and different diisocyanates. The furan-containing diol is obtained from the reaction of furfurylamine and two equivalents of hydroxyalkyl acrylate. The resulting furan-bearing polyurethanes are reacted with fatty amine-based N-alkyl maleimides. The maleimide and furan functionalities undergo a Diels–Alder reaction, which allows for the covalent bonding of the hydrophobic side chains to the polyurethane backbone. The covalent bonding of the hydrophobic maleimides to the polyurethane backbone is proven by means of NMR. The influence of the functionalization on the surface properties of the resulting polyurethane films is analyzed via the determination of surface energy via the sessile drop method.

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Bjelovic, Zoran, Ivan Ristic, Jaroslava Budinski-Simendic, Mirjana Jovicic, Jelena Pavlicevic, Branka Pilic, and Suzana Cakic. "The investigation reaction kinetic for polyurethanes based on different types of diisocyanate and castor oil." Chemical Industry 66, no. 6 (2012): 841–51. http://dx.doi.org/10.2298/hemind111216014b.

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The formation of polyurethanes based on vegetable oils is very complex and thus for industrial production of this materials it is important to determine the optimal temperature for polymerisation and finally to obtain materials with the proper mechanical properties. The goal of this work was to assess the kinetic of catalysed and noncatalysed reactions for polyurethanes based on castor oil as the polyol component and different types of diisocyanates. Due to the presences of hydroxyl groups on ricinoleic acid, castor oil is suitable for polyurethane preparation. The differential scanning calorimetry has been employed to study the polyurethane formation reaction using Ozawa isoconversion method. It was estimated that the catalyst addition decreases the activation energy. The highest reduction of activation energy was observed for the reactive systems with hexamethylene diisocyanate. Validity of obtained kinetic model was examined by FTIR spectroscopy following the apsorption of reactive groups. Obtained results of mechanical characteristics of the polyuretahane networks (with different NCO/OH ratio) confirmed that applied method could be used for prediction of optimal reaction condition in polyurethane networks synthesis.

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Correia, Cristina Borges, and João C. Bordado. "Synthesis and Characterization of New Polyurethane Adhesives." Materials Science Forum 514-516 (May 2006): 843–47. http://dx.doi.org/10.4028/www.scientific.net/msf.514-516.843.

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Polyurethane adhesives provide excellent flexibility, impact resistance and durability. Polyurethanes are formed through the reaction of an isocyanate component with polyether or polyester polyols or other active hydrogen compounds. This paper refers to polyurethane adhesives made from polyester polyols with long aliphatic chains (up to 36 carbon atoms) and MDI (diphenylmethane-4,4’-diisocyanate). The polyester polyols have been made from dimer acids obtained from renewable sources and short chain diols. The polyols that were used presented different degrees of unsaturation. The influence of the different raw materials in the adhesives performance is studied. The polyurethanes were produced by reaction between quasi-stoichiometric quantities of polyol and MDI, at several temperatures. The reaction was carried under inert atmosphere and at temperatures below 100°C. Performance of the adhesives was tested by carrying adhesion, hardness and water absorption tests. Characterization of both the polyester polyols and polyurethane adhesives was carried by Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Magnetic Nuclear Resonance (NMR), X-Ray Diffraction (WAXD), Scanning RMN Imaging of 1H of Stray- Field b (MRI) and Brookfield viscometry.

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Briz-López, Eva Marina, Rodrigo Navarro, Héctor Martínez-Hernández, Lucía Téllez-Jurado, and Ángel Marcos-Fernández. "Design and Synthesis of Bio-Inspired Polyurethane Films with High Performance." Polymers 12, no. 11 (November 17, 2020): 2727. http://dx.doi.org/10.3390/polym12112727.

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In the present work, the synthesis of segmented polyurethanes functionalized with catechol moieties within the hard or the soft segment is presented. For this purpose, a synthetic route of a new catechol diol was designed. The direct insertion of this catechol-free derivative into the rigid phase led to segmented polyurethanes with low performance (σmax ≈ 4.5 MPa). Nevertheless, when the derivative was formally located within the soft segment, the mechanical properties of the corresponding functionalized polyurethane improved considerably (σmax ≈ 16.3 MPa), owing to a significant increase in the degree of polymerization. It is proposed that this difference in reactivity could probably be attributed to a hampering effect of this catecholic ring during the polyaddition reaction. To corroborate this hypothesis, a protection of the aromatic ring was carried out, blocking the hampering effect and avoiding secondary reactions. The polyurethane bearing the protected catechol showed the highest molecular weight and the highest stress at break described to date (σmax ≈ 66.1 MPa) for these kind of catechol-functionalized polyurethanes. Therefore, this new approach allows for the obtention of high-performance polyurethane films and can be applied in different sectors, benefiting from the molecular adhesion introduced by the catechol ring.

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Jiang, Lin, Filippo Berto, and Dan Zhang. "Pyrolysis Kinetics and Flammability Evaluation of Rigid Polyurethane with Different Isocyanate Content." Molecules 26, no. 8 (April 20, 2021): 2386. http://dx.doi.org/10.3390/molecules26082386.

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Polyurethane (PU) is a typical product of the reaction between isocyanate and polyol, whose ratio would greatly influence material properties. In this paper, to investigate the influence of isocyanate on PU thermal stability and flammability, three kinds of rigid polyurethanes (RPUs) with different isocyanate ratio (1.05, 1.1, and 2.0) were manufactured in a laboratory and employed to have a series of TG (thermogravimetry), DSC (differential scanning calorimetry), and cone calorimetry tests. Kissinger’s method was used to calculate the activation energy and judge their stabilities. However, for such a complex degradation which consists of five reactions, it does not make sense by Kissinger method to obtain only two peak active energies. Considering complexity of PU degradation in air, genetic algorithm (GA) was employed to calculate kinetic triplets of five sub-reactions. The effects of isocyanate contents on each sub-reaction stability were obtained and then analyzed. By cone calorimeter testing, we found that great differences in heat release rate data. However, DSC analysis showed a complete opposite changed trend. Such difference is caused by DSC and calorimeter’s sample morphology, the former using grinded polyurethane powders but the latter polyurethane foam block.

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Yang, Zhe, Yan Bin Zhu, Fang Peng, and Chang Qing Fu. "Preparation and Application of Undecylenate Based Diol for Bio-Based Waterborne Polyurethane Dispersion." Advanced Materials Research 955-959 (June 2014): 88–91. http://dx.doi.org/10.4028/www.scientific.net/amr.955-959.88.

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The undecylenate based diol (UAD) has been synthesized from undecylenate by esterification and thiol-ene click reaction sequently, and then it was used as a diol to prepare bio-based waterborne polyurethane (WPU) reacting with isophorone diisocyanate (IPDI) and castor oil-based carboxyl hydrophilic chain extender. The structure of undecylenate based diol was verified by hydrogen proton nuclear magnetic resonance (1H NMR). Fourier transform infrared spectroscopy (FT-IR) was used to characterize the structure of WPU film. Furthermore, particle size and viscosity were used to character apparent properties of the bio-based waterborne polyurethane dispersion. The result shows that: bio-based waterborne polyurethane dispersion is transparent and very stable under room temperature. This work provides a simple and efficient method for the preparation of fatty acids based polyols and bio-based waterborne polyurethanes.

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Oprea, Stefan. "Synthesis and Properties of Unsaturated Poly(Urethane-Imide)s." High Performance Polymers 15, no. 3 (September 2003): 291–99. http://dx.doi.org/10.1177/0954008303015003006.

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Unsaturated poly(urethane-imide)s were prepared by the reaction of unsaturated polyurethane prepolymers with maleic anhydride. The polyurethane prepolymers were synthesized by the reaction of 4,4′-methylene diphenyl diisocyanate (MDI) with unsaturated polyesters having a molecular weight of about 500 or with a mixture of unsaturated and saturated polyesters having a molecular weight of about 2000. The unsaturated polyurethane prepolymers reacted with maleic anhydride until the evolution of carbon dioxide ceased to yield unsaturated poly(urethane-imide)s. These polymers exhibited improved solubility in organic solvents and formed flexible films showing fairly good stress-strain properties. Compared to conventional polyurethanes based on MDI and poly(ethylene glycol adipate) these polymers exhibited better thermal stabilities due to the presence of the imide groups.

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Datta, J., and J. T. Haponiuk. "Influence of Glycols on the Glycolysis Process and the Structure and Properties of Polyurethane Elastomers." Journal of Elastomers & Plastics 43, no. 6 (September 2, 2011): 529–41. http://dx.doi.org/10.1177/0095244311413447.

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In this work, the influence of glycols on the glycolysis process and the properties of obtained polyurethanes were investigated. The glycolysates were produced via glycolysis of waste polyurethane foam in the reaction with one of the following glycols: 1,3-propanediol, 1,5-pentanediol, and 1,6-hexanediol.The reactions were carried out for different mass ratios of polyurethane wastes to glycolysis agent, i.e. 6:1, 8:1, and 10:1. Polyurethanes were synthesized from the obtained intermediates by a one-step method of mixing polymeric di-isocyanate and the glycolysis products with molecular masses ranging from 700 to 1000, while a polyol (Poles 55/20) was used as a chain elongation agent. The influence of glycolysates on tensile strength and elongation at break of polyurethanes was investigated using a Zwick universal tensile tester. Thermal decomposition of the obtained glycolysates and polyurethanes was investigated by thermogravimetry coupled with Fourier transform infrared spectroscopy. It has been found that of all used glycols, 1,6-hexanediol gives the best improvement in the thermal stability of polyurethanes during the glycolysis process. The mean hardness of polyurethanes decreases but rebound resilience increases with chain length of the glycol used for obtaining glycolysates.

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Chen, Lijun, and Wei Jiang. "Modification of polyurethane with novel blocking agent." Pigment & Resin Technology 43, no. 2 (February 25, 2014): 97–103. http://dx.doi.org/10.1108/prt-04-2013-0030.

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Purpose – Fluorinated polyurethane combines some virtues of polyurethane and fluorinated polymer, such as low water absorption, attractive surface properties, good wearability and high weatherability. Fluorocarbon chains have been incorporated into polyurethanes by fluorinated diisocyanates, chain extenders, polyether glycols, polyester glycols and end-cappers. However, the fluorinated polyurethane, which is prepared with monohydric fluorocarbon alcohol, is seldom reported. The purpose of this research is to prepare and apply the novel fluorocarbon alcohols with side chain to modify polyurethane as the blocking agent. Design/methodology/approach – The novel fluorocarbon alcohol with side chain 2-methoxy-3-nonene perfluorinated oxygen propanol (MNPOP) can be prepared via alcoholysis reaction of methanol and 2,3-epoxypropyl perfluorinated nonene ether (EPPNE), which was prepared with etherification of hexafluoropropene trimer (HFPT) and 2,3-glycidol. Structures of EPPNE and MNPOP are confirmed with FTIR and NMR. The polyurethane can be modified when MNPOP is used as blocking agent. Findings – In comparison with the conventional polyurethane, the hydrophobic property of fluorinated polyurethane is improved. However, the increase of tensile strength of modified polyurethane is not obvious because MNPOP belongs to monohydric alcohol. And the function of MNPOP in the modified polyurethane is the blocking agent. The thermal stability of conventional and modified polyurethane is almost the same because MNPOP is de-blocked and fluorocarbon chains have not been incorporated into polyurethanes when the temperature is more than 150°C. Originality/value – The polyurethane is modified with the novel fluorocarbon alcohols with side chain, which functions as the blocking agent. The hydrophobic property of fluorinated polyurethane is improved.

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Lee, Jong Baek, Kwang Hyun Lee, Byung Chul Kang, Byung Won Kang, Sang Ll Lee, and Jin Kyung Lee. "Thermal Properties of a Liquid-Crystalline Polyurethanes Containing Biphenyl Mesogen." Key Engineering Materials 321-323 (October 2006): 1385–88. http://dx.doi.org/10.4028/www.scientific.net/kem.321-323.1385.

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A new type of thermotropic main-chain liquid crystalline polyurethanes containing biphenyl units was synthesized by polyaddition reaction of diisocyanates such as 2,6-tolylene diisocyanate, 2,5-tolylene diisocyanate, 2,4-tolylene diisocyanate, and 1,4-phenylene diisocyanate, with 4,4′-Bis(11-hydroxyundeyloxy)biphenyl (BP11). The structure of the monomer and the corresponding polymers were confirmed FT-IR and 1H NMR spectroscopic methods. BP11 exhibited a smectic type mesophase, however, nematic phase was found for all synthesized liquid crystalline polyurethanes except for 1,4-phenylene diisocyanate/BP11 based polyurethane. For example, polyurethane 2,5-TDI/BP11 exhibited monotropic liquid crystallinity in the temperature ranges from 173 to 156 °C on the cooling stage.

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Chen, Caihong, Zhening Yang, Fengxian Qiu, Feiyan Ye, Guorong Cao, Yijun Guan, and Dongya Yang. "Novel three chiral azobenzene polyurethanes: Preparation, optical properties and simulation comparisons of two different polymeric thermo-optic switches." Journal of Nonlinear Optical Physics & Materials 24, no. 03 (September 2015): 1550028. http://dx.doi.org/10.1142/s0218863515500289.

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Three different structures of chiral side-chain azobenzene polyurethane (CAPU-1), chiral graft azobenzene polyurethane (CAPU-2) and chiral bisazo polyurethane (CAPU-3) were prepared by diazo coupling reaction. The structures, thermal, mechanical properties, refractive index (n) and transmission loss of CAPU-1~3 were investigated. The Y-branch and Mach–Zehnder polymeric thermo-optic switches were simulated based on the synthesized three chiral azo polyurethanes as waveguide materials. The response time differences are owing to the different substituents and structure of the azo compound. The conclusion had potential significance to improve and develop the new digital optical and thermo-optic switch (TOS) with short response time and low driving power.

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Pavlicevic, Jelena, Mirjana Jovicic, Vesna Simendic, Oskar Bera, Radmila Radicevic, and Milena Spírková. "Modification of epoxy resins with thermoplastic segmented polycarbonate-based polyurethanes." Chemical Industry 68, no. 6 (2014): 755–65. http://dx.doi.org/10.2298/hemind130904086p.

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In this work, epoxy hybrid materials were synthesized by addition of thermoplastic segmented aliphatic polyurethanes with good elastic properties. The modified epoxy samples were obtained by curing of previously homogenized mixture of prepared polyurethane melts, epoxy resin and crosslinking agent Jeffamine D-2000. The influence of different weight content of polyurethanes (5, 10 and 15 wt. % compared to pure epoxy resin) as well the influence of different hard segments of elastomers (20, 25 and 30 wt. %) on the curing of modified epoxy systems was studied. The curing was followed by differential scanning calorimetry (DSC), in dynamic regime from 30 to 300?C, at three heating rates (5, 10 and 20?C/min). With the increase of hard segments content of polyurethanes added in higher concentration (10 and 15 wt. %) into epoxy matrix, the temperature of maximum ratio of curing was shifted to lower values (from 205 to 179?C). Obtained DSC data were analyzed using two integral methods (Ozawa-Flynn-Wall and Kissinger-Akahira-Sunose) and one differential kinetic model (Friedman). The significant differences were observed in the second part of the epoxy curing (for the reaction degrees higher than 60 %), where the values of activation energies remarkably increase. The addition of polyurethane elastomers retarded the curing process due to decreased mobility of reactant molecules caused by higher viscosity of reaction mixture. By detailed analysis of determined kinetic parameters, it is concluded that the influence of slow diffusion is more pronounced in the presence of thermoplastic polycarbonate-based polyurethanes, which confirmed their effect on the mechanism of epoxy curing. The highest tensile strength and hardness showed the DGEBA modified with the polyurethane with highest hard segment content. Increasing the hard segment content of polyurethane and its concentration in matrix, the tensile strength of modified epoxy was increased. The elongation at break of modified epoxy samples was significantly improved by addition of polycarbonate-based polyurethanes with low hard segment content, due to higher content of flexible soft segment chains.

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Lee, Jong Baek, and Byung Won Kang. "Synthesis and Properties of Thermotropic Main-Chain Type Liquid Crystalline Polyurethanes Containing Biphenyl Mesogen." Key Engineering Materials 342-343 (July 2007): 729–32. http://dx.doi.org/10.4028/www.scientific.net/kem.342-343.729.

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A new type of thermotropic main-chain liquid crystalline polyurethanes containing biphenyl units was synthesized by polyaddition reaction of diisocyanates such as 2,6-tolylene diisocyanate, 2,5-tolylene diisocyanate, 2,4-tolylene diisocyanate, and 1,4-phenylene diisocyanate, with 4,4′-Bis(8-hydroxyoctoxy)biphenyl (BP8). The structure of the monomer and the corresponding polymers were confirmed using FT-IR and 1H-NMR spectroscopic methods. BP8 exhibited a smectic type mesophase, however, nematic phases were found for all synthesized liquid crystalline polyurethanes except for 1,4-phenylene diisocyanate/BP8 based polyurethane. For example, polyurethane 2,5-TDI/BP8 exhibited monotropic liquid crystallinity in the temperature ranging from 172 to 160 °C on the cooling stage. Properties of these polyurethanes were studied by differential scanning calorimetry (DSC), and optical polarizing microscopy. The FT-IR study indicated that the hydrogen bonding among urethane linkages attributed to the mesomorphism.

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Taylor, Richard T., and Uraiwan Puapaiboon. "Polyurethane dendrimers via Curtius reaction." Tetrahedron Letters 39, no. 44 (October 1998): 8005–8. http://dx.doi.org/10.1016/s0040-4039(98)01787-0.

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Vimalasiri, P. A. D. T., R. P. Burford, and J. K. Haken. "Chromatographic Analysis of Elastomeric Polyurethanes." Rubber Chemistry and Technology 60, no. 3 (July 1, 1987): 555–77. http://dx.doi.org/10.5254/1.3536140.

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Abstract Both alkali and acid fusion reactions can be used to cleave polyurethane polymers successfully. Fusion reaction rates are much faster than conventional aqueous alkali or acid fusion methods. Separation of fragments could be carried out using the liquid-liquid extraction procedures described. After quantitative and qualitative analysis of fragments using GC, SEC, and HPLC, chemical structure of the polymer can be established. Although the work described uses only elastomeric polyurethanes for the development of the analytical schemes, these schemes can be used to analyze other types of polyurethanes such as “Spandex” fibers, adhesive coating films, and plastics. The procedures described have also been used for the analysis of polyamide resins which are condensation products.

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Prisacariu, Cristina, and Ion Agherghinei. "REACTIONS IN SOLID STATE WITHIN POLYURETHANES. KINETICS AND POSTCURE REACTION MECHANISM IN CASTING POLYURETHANE ELASTOMERS." Journal of Macromolecular Science, Part A 37, no. 7 (June 22, 2000): 785–806. http://dx.doi.org/10.1081/ma-100101123.

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Raouf, Raouf Mahmood, Hadeel A. Abdalgane, and Rand Salih Al-Jadiri. "Use of Simulation to Enhance the Performance of Sustainable Bio-Based Polyurethan Fome." Defect and Diffusion Forum 398 (January 2020): 60–66. http://dx.doi.org/10.4028/www.scientific.net/ddf.398.60.

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The needs to replace petroleum-based polyol by bio-source polyol in polyurethane industry were increased dramatically in the last few decades. The main obstacles associating with using bio-based polyol where the change in foam density and foam shrinkage. The reacting monomer was preheated to achieve a higher maximum reaction temperature that allows more setting of the cell structure and more stable foam matrix to overcome the vacuum forces and prevent density change and foam shrinkage. A simulation code for polyurethane reaction was used to find the optimum recipes with low catalyst loading to achieve a polyurethane foam with good properties.

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Zahedifar, Pegah, Lukasz Pazdur, Christophe M. L. Vande Velde, and Pieter Billen. "Multistage Chemical Recycling of Polyurethanes and Dicarbamates: A Glycolysis–Hydrolysis Demonstration." Sustainability 13, no. 6 (March 23, 2021): 3583. http://dx.doi.org/10.3390/su13063583.

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The use of polyurethanes and, therefore, the quantity of its scrap are increasing. Considering the thermoset characteristic of most polyurethanes, the most circular recycling method is by means of chemical depolymerization, for which glycolysis is finding its way into the industry. The main goal of polyurethane glycolysis is to recover the polyols used, but only limited attempts were made toward recovering the aromatic dicarbamate residues and derivates from the used isocyanates. By the split-phase glycolysis method, the recovered polyols form a top-layer phase and the bottom layer contain transreacted carbamates, excess glycol, amines, urea, and other side products. The hydrolysis of carbamates results in amines and CO2 as the main products. Consequently, the carbamates in the bottom layer of polyurethane split-phase glycolysis can also be hydrolyzed in a separate process, generating amines, which can serve as feedstock for isocyanate production to complete the polyurethane material cycle. In this paper, the full recycling of polyurethanes is reviewed and experimentally studied. As a matter of demonstration, combined glycolysis and hydrolysis led to an amine production yield of about 30% for model systems. With this result, we show the high potential for further research by future optimization of reaction conditions and catalysis.

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Gao, Jun Gang, Feng Li Zhu, Jiang Bo Yang, and Xiao Qian Liu. "Synthesis and Curing Kinetics of UV-Curable Waterborne Bisphenol-S Epoxy Acrylate/Polyurethane-Acrylate Coating." Advanced Materials Research 549 (July 2012): 457–61. http://dx.doi.org/10.4028/www.scientific.net/amr.549.457.

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In ouder to prepare the waterborne UV-curable polyurethane acrylate coatings, the anionic polyurethane acrylate emulsifier and bisphenol-S eopxy acrylate were synthesized. The curing process, kinetics and properties of waterborone UV-curable epoxy acrylate/polyurethanes acrylate coating were investigated by FTIR, DSC and DMA. The results show that the static initial curing temperature Ti is 52.36 oC, peak temperature Tp is 71.58 oC, the finished temperature Tf is 89.15 oC. The curing reaction can be described by two-parameter autocatalytic Šesták-Berggren (S-B) model.This coating has a better UV-curing property. The dynamic mechanical analysis showed that the glass transition temperature Tg of coating film is 52.70 oC.

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Wang, Tzong-Liu, Chin-Chung Yu, Chien-Hsin Yang, Yeong-Tarng Shieh, Yu-Zen Tsai, and Na-Fu Wang. "Preparation, Characterization, and Properties of Polyurethane-Grafted Multiwalled Carbon Nanotubes and Derived Polyurethane Nanocomposites." Journal of Nanomaterials 2011 (2011): 1–9. http://dx.doi.org/10.1155/2011/814903.

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We incorporated hydroxyl groups into the polyurethane backbone and then used the “grafting to” approach to functionalize the multiwalled carbon nanotubes (MWNTs) via the esterification reaction between MWNTs and segmented polyurethanes (PUs). X-ray photoelectron spectroscopy (XPS) spectra showed that the sidewalls of MWNTs had been functionalized with acid treatment, and the amount of COOH increased with increasing acid treatment time. FTIR spectra further confirmed that PU was covalently attached to the sidewalls of MWNTs. The functionalized acid amount and the grafted PU amount were determined by thermogravimetric analyses (TGAs). Comparative studies based on SEM images of the PU-functionalized and chemically defunctionalized MWNT samples also revealed the covalent coating character. Dynamic mechanical analysis (DMA) of nanocomposite films prepared from PU and PU-functionalized MWNTs showed enhanced mechanical properties and increased soft segment . Tensile properties indicated that PU-functionalized MWNTs were effective reinforcing fillers for the polyurethane matrix.

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Yu, Yitao, Jing Wang, and Xu Wang. "Synthesis and properties of polysiloxane graft waterborne polyurethane modified with α-N,N-dihydroxyethylaminopropyl-ω-butylpolydimethylsiloxane." Journal of Polymer Engineering 33, no. 6 (September 1, 2013): 527–33. http://dx.doi.org/10.1515/polyeng-2013-0050.

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Abstract In this study, α-N,N-dihydroxyethylaminopropyl-ω-butylpolydimethylsiloxane was used to prepare waterborne polyurethane-polysiloxane graft copolymer dispersions. α-N,N-dihydroxyethylaminopropyl-ω-butylpolydimethylsiloxane was synthesized via hydroxyl protection, alkylation, anionic ring-opening polymerization, hydrosilylation, and deprotection. Waterborne polyurethane-polysiloxane graft copolymers were prepared by the reaction of poly propylene glycol (PPG), toluene diisocyanate (TDI), 2,2-dimethylol propionic acid (DMPA), 1,4-butanediol (BDO), and α-N,N-dihydroxyethylaminopropyl-ω-butylpolydimethylsiloxane. The water absorption of copolymer films decreased from 163.9 to 17.3% when polysiloxane content increased from 0 to 5%. The tensile strength of the copolymer films increased from 14.0 MPa to 26.3 MPa and decreased when polysiloxane content was more than 3%. The results revealed that the properties of waterborne polyurethane-polysiloxane graft copolymer dispersions and films were improved by grafting polysiloxane chains to polyurethanes.

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Hashida, T., T. Ueno, H. Nakamoto, and M. Suzuki. "Improvement of Thermal Insulation for Polyurethane Foam by the Conversion of Carbon Dioxide to an Organic Carbonate Compound." High Performance Polymers 10, no. 1 (March 1998): 81–91. http://dx.doi.org/10.1088/0954-0083/10/1/010.

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A new method to improve the thermal insulation of polyurethane rigid foam blown by a non-ozone depleting agent—an alternative to chlorofluorocarbon—has been developed. This method involves the reduction of the gas thermal conductivity for polyurethane foam by the conversion of gaseous carbon dioxide in the foam to an organic carbonate. We tried to perform the cyclization of carbon dioxide in foam with an epoxy compound, and then the reduction of the thermal conductivity of the polyurethane foam was ascertained as carbon dioxide was chemically fixed in the foam. Consequently, this method led to a reduction of about 10% in the thermal conductivity in comparison with that of the conventional foam including carbon dioxide. In addition, the degree of progress of reaction in the foam was investigated by a quantitative analysis of carbon dioxide, epoxide and the resulting cyclic carbonate in the polyurethane foam. It was observed that unnecessary reactions, which consumed epoxide other than for the fixation of carbon dioxide, existed in the process of urethane polymerization. The main unnecessary reaction was presumed to be a side reaction of epoxide with isocyanate. Furthermore, the unnecessary reactions were affected by the type of urethane catalyst, the selection of which has been of importance in this method.

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Zhang, Cui, Xinglin Tong, Chengwei Deng, Hongqiao Wen, Di Huang, Qian Guo, and Xinrui Liu. "The foaming dynamic characteristics of polyurethane foam." Journal of Cellular Plastics 56, no. 3 (July 29, 2019): 279–95. http://dx.doi.org/10.1177/0021955x19864374.

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Polyurethane foam is a kind of polymer composite material. The foaming turgidity and reaction temperature of polyurethane foam are closely related to its mechanical properties. According to our present knowledge, this study is the first time that fiber optic sensing technology has been applied to monitor the dynamics change in the foaming turgidity and reaction temperature of polyurethane foam during its preparation. The effects on the foaming expansion force, contractile force, and reaction temperature are studied through changing proportion of water among the ingredients of the polyurethane foam. The results have shown that the fiber optic Bragg grating wavelength varies due to the reaction temperature and foaming power. In the reaction process, the foaming expansion force can make the maximum wavelength change of fiber optic Bragg grating 1–3.5 nm, equivalent to 1000–3541 micro strain. And the highest temperature of the reaction was 42.6°C. The wavelength shifts of the fiber optic Bragg gratings were closely related to the reaction temperature and foaming power. The results show that fiber optic sensing technology can be used for the online kinetics monitoring of the reaction process of polyurethane foam plastics. The data obtained from the fiber optic Bragg grating could be used for the design and performance prediction of new polyurethane foam materials.

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Chu, Fu Qiang, and Xiang Jiao Wu. "Water-Based UV-Curable Polyurethane Based on Wheat Straw Lignin Obtained by Ethanol Extraction." Advanced Materials Research 295-297 (July 2011): 278–81. http://dx.doi.org/10.4028/www.scientific.net/amr.295-297.278.

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The aim of this paper is to discuss the application of ethanol-dissolved lignin in preparing high value products. Lignin was extracted from wheat straw by ethanol and used to prepare water-based UV-curable polyurethane. The preparation of water-based UV-curable polyurethane was completed by a three-step reaction. Besides lignin, toluene- 2, 4- diisocyanate (TDI), dimethylolpropionic acid (DMPA), 2-hydroxyethyl acrylate (HEA) and polyether glycol (PPG) were used. The effect of lignin content on the synthesis process was studied. The prepared lignin polyurethane was neutralized with tertiary amine (TEA) and dispersed in water. The properties of the final product, for example, rheological property, average particle size, UV-curing ability and mechanical property, etc. were characterized. Results indicated that the lignin polyurethanes could cure quickly and the presence of lignin with a proper proportion during the synthesis had a positive effect on the tensile strength of cured film.

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Xu, Kang, Xiaojun Liu, Leran Bu, Hena Zhang, Caihong Zhu, and Yuling Li. "Stimuli-Responsive Micelles with Detachable Poly(2-ethyl-2-oxazoline) Shell Based on Amphiphilic Polyurethane for Improved Intracellular Delivery of Doxorubicin." Polymers 12, no. 11 (November 10, 2020): 2642. http://dx.doi.org/10.3390/polym12112642.

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Polyurethanes (PUs) have various biomedical applications including controlled drug delivery. However, the incompletely release of drug at tumor sites limits the efficiency of these drug loaded polyurethane micelles. Here we report a novel polymer poly(2-ethyl-2-oxazoline)-SS-polyurethane-SS-poly(2-ethyl-2-oxazoline) triblock polyurethane (PEtOz-PU(PTMCSS)-PEtOz). The hydrophilic pH-responsive poly(2-ethyl-2-oxazoline) was used as an end-block to introduce pH responsiveness, and the hydrophobic PU middle-block was easily synthesized by the reaction of poly (trimethylene carbonate) diol containing disulfide bonds (PTMC-SS-PTMC diol) and bis (2-isocyanatoethyl) disulfide (CDI). PEtOz-PU(PTMCSS)-PEtOz could self-assemble to form micelles (176 nm). The drug release profile of PEtOz-PU(PTMCSS)-PEtOz micelles loaded with Doxorubicin (DOX) was studied in the presence of acetate buffer (10 mM, pH 5.0) and 10 mM dithiothreitol (DTT). The results showed that under this environment, DOX-loaded polyurethane micelles could release DOX faster and more thoroughly, about 97% of the DOX was released from the DOX-loaded PEtOz-PU(PTMCSS)-PEtOz micelle. In addition, fluorescent microscopy and cell viability assays validated that the DOX-loaded polyurethane micelle strongly inhibits the growth of C6 cells, suggesting their potential as a new nanomedicine against cancer.

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Kostić, Marija, Suzana Cakić, Ivan Ristić, Milena Marinović-Cincović, Ljubiša Nikolić, and Suzana Samaržija-Jovanović. "Synthesis and characterization of pH-sensitive saccharide modified Polyurethane hydrogels: Effect of polyol, crosslinker and acid chain extender." Advanced Technologies 10, no. 1 (2021): 29–36. http://dx.doi.org/10.5937/savteh2101029k.

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Biodegradable polyurethanes can be the basis for drug delivery systems that are sensitive to external changes. pH-sensitive polyurethanes (PUs) have been used successfully as intravaginal rings and specific drug delivery systems for the colon. In this study, a series of pH-sensitive polyurethane hydrogels with a change of the polyol component (poly(ethylene glycol) 400/poly(propylene glycol) 2000/poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) 1100), saccharides as crosslinkers (melibiose/raffinose/starch) and a-hydroxy carboxylic acids as chain extenders (dimethylol propionic acid/lactic acid) were synthesized. Structural characterization of the synthesized polyurethane hydrogels was performed using Fourier transform infrared spectroscopy (FTIR), which showed that the polyurethane synthesis reaction was achieved with successful crosslinking with saccharides and, despite the change of starting components, FTIR spectra for all investigated samples are almost identical. The degree of swelling of the hydrogels was monitored at 25 °C in solutions of pH values 4.5 and 7.4. In samples with the polyol component block1100, the degree of swelling at pH 7.4 (16.09%) was up to 9 times higher than at pH 4.5 (1.82%). The effects of variable parameters on the thermal properties and phase transitions of PUs hydrogels were investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results showed that by varying the saccharide as a crosslinker, the acid chain extender and the chain length of the polyols, the stated properties of polyurethane hydrogels as potential drug delivery carriers can be influenced.

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27

Wagenführ-Júnior, Jorge, Jurandir Marcondes Ribas Filho, Marcelo Mazza do Nascimento, Fernanda Marcondes Ribas, Marcus Vinícius Wanka, and Andressa de Lima Godoi. "Histopathological reaction over prosthesis surface covered with silicone and polyurethane foam implanted in rats." Acta Cirurgica Brasileira 27, no. 12 (December 2012): 866–73. http://dx.doi.org/10.1590/s0102-86502012001200007.

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PURPOSES: To evaluate whether polyurethane foam leads more intense foreign-body reaction than silicone foam. To compare the vascularization of the capsules surrounding the foam implants. To investigate if the capsule of polyurethane foam implanted has greater amount of collagen than that of silicone foam. METHODS: Sixty-four young male Wistar rats were allocated into two groups: polyurethane foam and silicone foam. Subcutaneous discs were implanted into the dorsum of the animals in both groups. The capsules were assessed 28 days, two months, three months and six months postoperatively. Microscopic analysis with H&E stain was performed to evaluate the acute and chronic inflammatory process, foreign-body reaction and neovascularization. The analysis with picrosirius red was performed using the ImageProPlus software, to measure the number of vessels and collagen types I and III. RESULTS: There were no statistical differences between the two groups regarding the acute and chronic inflammatory processes. All rats from the polyurethane group, in all times, exhibited moderate or intense foreign-body reaction, with statistic significant difference (p=0.046) when compared with the silicone group, in which the reaction was either mild or nonexistent at two months. Vascular proliferation was significantly different between the groups at 28 days (p=0.0002), with the polyurethane group displaying greater neovascularization with H&E stain. Similar results were obtained with picrosirius red, which revealed in the polyurethane group a much greater number of vessels than in the silicone group (p=0.001). The collagen area was larger in the polyurethane group, significantly at 28 days (p=0.001) and at two months (p=0.030). CONCLUSIONS: Polyurethane foam elicited more intense foreign-body reaction when compared with silicone foam. The number of vessels was higher in the capsules of the polyurethane foam implants 28 days after the operation. The capsule of the polyurethane foam implants showed a greater amount of collagen than that of the silicone foam implants.

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Wang, Ruitao, Chunxiang Li, Zhaohua Jiang, and Zhijiang Wang. "Self-Assembly of Amphiphilic Linear−Dendritic Carbosilane Block Surfactant for Waterborne Polyurethane Coating." Polymers 12, no. 6 (June 9, 2020): 1318. http://dx.doi.org/10.3390/polym12061318.

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The traditional two-component waterborne polyurethane coating system cannot effectively inhibit the undesirable side reaction between polyisocyanate and water during curing hardening. It is difficult to avoid the microbubbles formed by this reaction during the film formation process, which severely degrades the appearance and decreases the performance of the film. Therefore, the addition of an amphiphilic Linear-Dendritic carbosilane Block Surfactant (LDBS) to the hardener can physically separate the polyisocyanate emulsion from water through self-assembly. The bubble-free film thickness (BFFT) of the two-component waterborne polyurethane coating in this study is approximately 1.5-fold greater than commercial waterborne polyurethane coatings in today’s coating industry. Fourier transform infrared spectroscopy (FT-IR) varied the effectiveness of LDBS for inhibition of the undesirable side reaction. The successful application of the waterborne polyurethane coating with LDBS on the 600 km/h high-speed maglev train provides a technical solution for large-scale industrialization of waterborne polyurethane coating and complete replacement of solvent polyurethane coating.

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29

Komez, Aylin, Senem Buyuksungur, Vasif Hasirci, and Nesrin Hasirci. "Effect of chemical structure on properties of polyurethanes: Temperature responsiveness and biocompatibility." Journal of Bioactive and Compatible Polymers 33, no. 5 (June 28, 2018): 479–97. http://dx.doi.org/10.1177/0883911518783233.

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Polyurethanes are known as one of the most biocompatible and inherently blood-compatible materials and have a wide range of applications in the medical field due to their controllable structure and properties. Durability, elasticity, elastomeric structure, fatigue resistance, versatility, and easy acceptance by the biological media after the application makes these polymers preferable in medical area. In this study, polyurethane films were prepared using poly(propylene-ethylene glycol) and either toluene-2,4-diisocyanate or 4,4′-methylenediphenyl diisocyanate without adding any other ingredients such as solvent, catalyst, or chain extender to prevent negative effects of leachable molecules. Mechanical tests were performed at room temperature while swelling tests were conducted in water and phosphate-buffered saline at 4°C, 25°C, and 37°C. Temperature responsiveness was observed for the samples synthesized using toluene-2,4-diisocyanate and poly(propylene-ethylene glycol). These samples had more than 100% swelling at 4°C and about 4% swelling at 25°C and 37°C. Cytocompatibility tests were performed by culturing the samples and their extracts with mouse fibroblast cells (L929). Viability of human umbilical vein endothelial cells was studied to examine the compatibility of the films for blood contacting devices. Both toluene-2,4-diisocyanate and 4,4-methylenediphenyl diisocyanate–based polyurethane films showed no cytotoxic effect and good biocompatibility. Oxygen plasma treatment enhanced hydrophilicity of the films. After plasma treatment, human umbilical vein endothelial cell attachment on toluene-2,4-diisocyanate–based polyurethane films improved and 4,4-methylenediphenyl diisocyanate–based polyurethane films maintained their high cell affinity. Polyurethanes presenting temperature responsiveness, high biocompatibility, and high affinity for human umbilical vein endothelial cells were synthesized in medical purity and in a reaction media involving only diisocyanate and diol components without addition of any solvent, chain extender, or catalyst. Polyurethanes with these properties and as produced in this study are reported for the first time in the literature.

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30

Marin, Laurentiu, Topala Pavel, Catalina Daniela Marin, and Teodor Sandu. "Physical Training Methods For Mine Rescuers In 2015." ACTA Universitatis Cibiniensis 66, no. 1 (July 1, 2015): 108–13. http://dx.doi.org/10.1515/aucts-2015-0037.

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Abstract Research and development activities presented were aimed at obtaining a nanocomposite polyurethane matrix with special anti-wear, anti-slip and fire-resistant properties. Research and development works were materialized by obtaining polyurethane nanocomposite matrix, by its physico-chemical modification in order to give the desired technological properties and by characterization of the obtained material. Polyurethane nanocomposite matrix was obtained by reacting a PETOL 3 type polyetherpolyol (having a molecular weight of 5000 UAM) with a diisocyanate under well-established reaction conditions. Target specific technological properties were obtained by physical and chemical modification of polyurethane nanocomposite matrix. The final result was getting a pellicle material based on modified nanocomposite polyurethane, with anti-wear, anti-slip and fire-resistant properties, compatible with most substrates encountered in civil and industrial construction: wood, concrete, metal.

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31

Ban, Jian Feng, Shao Rong Lu, and Chen Xi Zhang. "Synthesis and Characterization of Biphenylnate Liquid Crystalline Polyurethanes." Key Engineering Materials 428-429 (January 2010): 158–61. http://dx.doi.org/10.4028/www.scientific.net/kem.428-429.158.

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A series of novel biphenylnate liquid crystalline polyurethanes (BLCPs) were synthesized by polyaddition reaction of 4,4’-dihydroxybiphenyl with 2,4-TDI(2,4-toluenediisocyanate) and diethylene glycol through changing the molar ratio of diphenol and diol. The thermotropic properties, the melting point (Tm) and the isotropization temperature (Ti) of the synthesized polyurethanes were characterized by FT-IR, DSC, POM and WXRD. The results of experiments showed that all of the polyurethane polymers exhibited thermotropic liquid crystalline properties between 130°C and 230°C. The transition temperature (Tm and Ti) decreased with an increase in the length of the flexible chain.

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32

Chen, Yi, Wen Yong Liu, Guang Sheng Zeng, Xiang Gang Li, and Ling Gu. "Study on the Synthesis of Polyester Type Waterborne Polyurethane and Modifying by Nano-Sized Particles." Applied Mechanics and Materials 217-219 (November 2012): 656–60. http://dx.doi.org/10.4028/www.scientific.net/amm.217-219.656.

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The waterborne polyurethane was prepared by reaction between polyester polyol and isophorone diisocyanat, different nanoparticles were filled into the system for modification. The effect of different ratio of materials, the kinds and mass of nanoparticles on the characters of waterborne polyurethane latex and film were investigated. The results showed that the stable polyurethane latex and polyurethane film with perfect characters could be prepared when the ratio of NNCO/NOH was 2.5~3.0, the DMPA with a mass fraction of 5%~6% was added into reaction as a macromolecule extender after adding small molecule chain extender BPO. Filling nanoparticles into the polyurethane latex could improve the water resistance and mechanical characters of the film. Nano-sized SiO2 was a better modifier than TiO2, and the appropriate mass fraction of SiO2 was 6% of polyurethane raw materials.

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33

Zhang, Jian Sheng. "Synthesis of the Hydrogel Polyurethane." Advanced Materials Research 1033-1034 (October 2014): 34–38. http://dx.doi.org/10.4028/www.scientific.net/amr.1033-1034.34.

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The synthesis, blocking and unblocking technologic conditions of hydrogel polyurethane were researched. The results showed that it would improve the bonding strength of hydrogel polyurethane when the hydrophilic polyether polyol was mixed with lipophilic polyether polyol of 10%. And the prepolymer of water-soluble polyurethane was achieved with hydrophilic polyether polyol and lipophilic polyether polyol as the materials at a prepolymerization reaction temperature of 85°C with TDI and reaction time of 180min. Then the preferable result could be got at a choice of phenol as sealant which was used to seal the water-soluble polyurethane active group, n (-NCO):n (-OH)=1:1.2, dosage of dibutyltin dilaurate as catalyst of 0.3%, unblocking in hot water.

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34

Xi, Xuedong, Antonio Pizzi, Christine Gerardin, Hong Lei, Xinyi Chen, and Siham Amirou. "Preparation and Evaluation of Glucose Based Non-Isocyanate Polyurethane Self-Blowing Rigid Foams." Polymers 11, no. 11 (November 2, 2019): 1802. http://dx.doi.org/10.3390/polym11111802.

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A partially biobased self-blowing and self-hardening polyurethane foam from glucose-based non-isocyanate polyurethanes (g-NIPU) was prepared by reaction of glucose with dimethyl carbonate and hexamethylene diamine. However, these foam types generally require a high foaming temperature. In this paper, a self-blowing foam based on g-NIPU was prepared at room temperature by using maleic acid as an initiator and glutaraldehyde as a crosslinker. Water absorption, compression resistance, and fire resistance were tested. Scanning electron microscopy (SEM) was used to observe the foam cells structure. Middle infrared (ATR FT-MIR) and Matrix Assisted Laser Desorption Ionization Time-of-Flight (MALDI-TOF) mass spectrometry were used to help to analyze the reactions during the foaming process. The results obtained showed that self- blowing rigid foams have good compression, this being directly proportional to the foam density. Increasing the amount of glutaraldehyde or reducing maleic acid thickens the cell walls and increases the density of the foams. MALDI-TOF analysis showed that g-NIPU reacts with both maleic acid and glutaraldehyde. The foams presented poor fire resistance indicating that, as for isocyanate based polyurethane foams, addition of a fire retardant would be necessary.

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35

Cao, Chun Ping, Yu Sun, and Yu Li. "Optimization of Parameters in Fiber Reinforced Polyurethane Composited Reaction Injection Molding." Advanced Materials Research 748 (August 2013): 96–100. http://dx.doi.org/10.4028/www.scientific.net/amr.748.96.

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In order to explore effects of various processing parameters on the mechanical properties of jute fiber reinforced polyurethane foam composites, jute fiber reinforced polyurethane composites were prepared by variable fiber reinforced reaction injection technology. The influence of jute fiber contents, fiber length, mold pressure and fiber modification treatment to the impact toughness was analyzed by orthogonal test in this paper. The microstructure and fracture micrograph of impact fracture specimens were studied with scanning electron microscope (SEM). The results showed that the best impact performance was obtained while fiber content was 10%, fiber length was12.5mm, mold pressure was 80tons, and jute fibers were modified by alkali. Furthermore, the result was compared with the corresponding research of glass fiber and carbon fiber reinforced polyurethane composites, and provided a theoretical basis for the application of the fiber reinforced polyurethane foam composites.

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Zheng, Yan Min, Jun Hui Zhang, and Zhao Gui Su. "Kinetics Study on Burning Performance of Polyurethane Foam." Applied Mechanics and Materials 174-177 (May 2012): 429–32. http://dx.doi.org/10.4028/www.scientific.net/amm.174-177.429.

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This article uses the thermal analysis to study the kinetics characteristics of Polyurethane foam. The partially oxidized and non oxidized materials were used to study the variation of reaction of the smoldering, and the mechanism of function and activation energy of two substances was obtained. The result show that the oxygenolysis of the non oxidized Polyurethane foam belongs to the second-level chemical reaction, while the oxygenolysis of partially oxidized belongs to the first-level chemical reaction; the oxidization reaction of Polyurethane foam is a process which have lots of reaction steps to mutual promote as well as connection with each steps ; Through the smoldering experiment verify that the response characteristics of the two substances under the same heat flux to a certain extent, and the results agree well with the calculated activation energy.

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37

Chen, Jian Bing, Qiang Guo, Jin Liang Sun, Xian Li Shao, and Zhi Jun Nie. "A Study on Linseed Oil Modified Waterborne Polyurethane Coatings." Materials Science Forum 686 (June 2011): 528–32. http://dx.doi.org/10.4028/www.scientific.net/msf.686.528.

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The waterborne polyurethane coatings modified by linseed oil were prepared in a method of ammonolysis. The influence of reaction time and temperature of the linseed oil ammonolysis on structure and properties of the waterborne polyurethane coatings was investigated and discussed. It has been shown in this work that the preferred ammonolysis temperature would be 102~118°C, the reaction time could be about 80 min, and structure of the modified waterborne polyurethane was analysed by FTIR. The touch-dry time of the modified waterborne polyurethane with drier would be shorter than that of non-modified waterborne polyurethane, normally in a week, and the stability of the modified waterborne polyurethane coating in water could stand for 3 months under room temperature. The TGA results of the coatings showed that the weight loss started at about 294°C.

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38

Ketata, N., C. Sanglar, H. Waton, S. Alamercery, F. Delolme, G. Raffin, and M. F. Grenier-Loustalot. "Thermal Degradation of Polyurethane Bicomponent Systems in Controlled Atmospheres." Polymers and Polymer Composites 13, no. 1 (January 2005): 1–26. http://dx.doi.org/10.1177/096739110501300101.

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Although the thermal degradation of polyurethanes has been extensively studied in the past, the use of a panoply of recent analytical techniques has provided more detailed data and enabled us to confirm prior findings on the thermal degradation of bicomponent polyurethanes. The thermal behaviour of bicomponent polyurethanes in conditions of controlled atmosphere and temperature was characterized by determining their heat stability by on-line TGA/FT-IR coupling and off-line TGA/TCT/GC/MS coupling in order to identify the volatile compounds released. Degradation residues were analyzed by FT-IR and MALDI-TOF (matrix assisted laser desorption/ionization coupled with time-of-flight) mass spectrometry. A major drawback of these thermoplastic elastomers is that one of the components, isocyanate, is toxic. Based on the data obtained with model urethane compounds ( p-TI-based) and bicomponent polyurethane polymer (MDI- and PEG-based), we show that the thermal degradations are different. The widespread application of these materials exposes them to extreme working conditions, which is why we propose reaction mechanisms for their degradation.

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39

Wang, Peng, Dietmar Auhl, Eckart Uhlmann, Georg Gerlitzky, and Manfred H. Wagner. "Rheological and Mechanical Gradient Properties of Polyurethane Elastomers for 3D-Printing with Reactive Additives." Applied Rheology 29, no. 1 (January 1, 2019): 162–72. http://dx.doi.org/10.1515/arh-2019-0014.

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Abstract Polyurethane (PU) elastomers with their broad range of strength and elasticity are ideal materials for additive manufacturing of shapes with gradients of mechanical properties. By adjusting the mixing ratio of different polyurethane reactants during 3D-printing it is possible to change the mechanical properties. However, to guarantee intra- and inter-layer adhesion, it is essential to know the reaction kinetics of the polyurethane reaction, and to be able to influence the reaction speed in a wide range. In this study, the effect of adding three different catalysts and two inhibitors to the reaction of polyurethane elastomers were studied by comparing the time of crossover points between storage and loss modulus G′ and G′′ from time sweep tests of small amplitude oscillatory shear at 30°C. The time of crossover points is reduced with the increasing amount of catalysts, but only the reaction time with one inhibitor is significantly delayed. The reaction time of 90% NCO group conversion calculated from the FTIR-spectrum also demonstrates the kinetics of samples with different catalysts. In addition, the relation between the conversion as determined from FTIR spectroscopy and the mechanical properties of the materials was established. Based on these results, it is possible to select optimized catalysts and inhibitors for polyurethane 3D-printing of materials with gradients of mechanical properties.

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40

Rémillard, B., T. Vu-Khanh, B. Fisa, and S. Naik. "Reaction injection molding of mica reinforced polyurethane." Polymer Composites 7, no. 5 (October 1986): 395–403. http://dx.doi.org/10.1002/pc.750070517.

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41

Kim, Jin, Wonjoo Lee, Taehee Kim, Hyeon-Gook Kim, Bongkuk Seo, Choong-Sun Lim, and In Cheong. "Synthesis of Thermally Stable Reactive Polyurethane and Its Physical Effects in Epoxy Composites." Applied Sciences 8, no. 9 (September 7, 2018): 1587. http://dx.doi.org/10.3390/app8091587.

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A flame retardant polyol (EP-DOPO) with epoxy functional groups was synthesized by reacting a 1,6-hexanediol glycidyl ether with a flame retardant 10-(2,5-dihydroxyphenyl)-10H-9-oxa-10-phospha-phenanthrene-10-oxide (DOPO). The polyurethane (EPPU) with enhanced heat resistance was prepared by the reaction of a polyol blend of EP-DOPO and polytetrahydrofuran (PolyTHF) at a ratio of 1:1 with isophorone diisocyanate. EPPU useful for the preparation of cables or coatings showed higher thermal decomposition temperature rather than that of reference polyurethane synthesized by the reaction between pure PolyTHF and isophorone diisocyanate by thermogravimetric analysis. Further study of the polyurethane as a toughening agent for epoxy polymers was carried out. Epoxy compositions consisting of bisphenol A epoxy resin and dicyandiamide as a hardener have a brittle property allowing crack propagation after cure. Polyurethane plays an important role as an impact modifier to prevent from cracks of epoxy polymers. Various contents of EPPU were added into epoxy compositions to measure the physical property changes of epoxy polymers. The tensile and flexural strengths of the cured specimen were compared with those of epoxy compositions including reference polyurethane. Furthermore, the crosslink density of the cured epoxy compositions was compared.

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42

Zarzyka-Niemiec, Iwona. "Reactions of N,N′-bis(2-hydroxyethyl)oxalamide with Ethylene Carbonate and Use of the Obtained Products as Components of Polyurethanes Foams." International Journal of Polymer Science 2010 (2010): 1–9. http://dx.doi.org/10.1155/2010/689837.

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-bis(2-hydroxyethyl)oxalamide (BHEOA) was subject to hydroxyalkylation with ethylene carbonate (EC). By means of instrumental methods (IR, -NMR, MALDI ToF, GC, and GC-MS), an influence of the reaction conditions on structure and compositions of the obtained products was investigated. The hydroxyalkyl and hydroxyalkoxy derivatives of oxalamide (OA) were obtained by reaction of BHEOA with 2–10-molar excess of ethylene carbonate (EC, 1,3-dioxolane-2-one). The products have a good thermal stability and possess suitable physical properties as substrates for foamed polyurethanes. The obtained products were used in manufacturing the rigid polyurethane foams which possess enhanced thermal stability and good mechanical properties.

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Oh, Cho-Rong, Sang-Hyub Lee, Jun-Hong Park, and Dai-Soo Lee. "Thermally Self-Healing Graphene-Nanoplate/Polyurethane Nanocomposites via Diels–Alder Reaction through a One-Shot Process." Nanomaterials 9, no. 3 (March 14, 2019): 434. http://dx.doi.org/10.3390/nano9030434.

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Thermally self-healing graphene-nanoplate/polyurethane (GNP/PU) nanocomposites were prepared via a bulk in-situ Diels–Alder (DA) reaction. Graphene-nanoplate (GNP) was used as a reinforcement and crosslinking platform by a DA reaction with a furfuryl-based chain extender of polyurethane (PU). Results showed that a DA reaction occurred in GNP during the PU forming cure process. This procedure is simple and solvent free because of the absence of any independent surface modification process. Through the calculation of the interfacial tensions, the conditions of the bulk in-situ DA reaction were determined to ensure that GNP and the furfuryl group can react with each other at the interface during the curing process without a solvent. The prepared composites were characterized in terms of thermal, mechanical, and thermally self-healing properties via the DA reaction. In the PU capable of a DA reaction (DPU), characteristic peaks of DA and retro DA reactions were observed in the Fourier transform infrared (FT-IR) spectroscopy and endothermic peaks of retro DA reactions appeared in differential scanning calorimetry (DSC) thermograms. The DPU showed significantly enhanced physical properties and chemical resistance. The thermally self-healing capability was confirmed at 110 °C via the retro DA reactions. It is inferred that thermally self-healable crosslinked GNP/PU nanocomposites via DA reactions could be prepared in a simple bulk process through the molecular design of a chain extender for the in-situ reaction at the interface.

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44

Jia, Ruo Kun, Yang Yu, Song Zhu Lin, and Na Bai. "Kinetics of TiO₂/Polyurethane Films for Degradation of Organic Pollutants in Water." Advanced Materials Research 610-613 (December 2012): 1560–64. http://dx.doi.org/10.4028/www.scientific.net/amr.610-613.1560.

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In this paper,TiO2was prepared by the sol-gel Method,which has high activity and oxidation abilities .The polyurethane is famous for its transmittance and film forming properties,we use polyurethane and titanium dioxide to produce TiO2/polyurethane films. In this paper, phenolic wastewater was considered as the research object,Discussed photocatalytic properties and photocatalytic reaction kinetics model of TiO2/polyurethane film at 253.7nm UV irradiation.The results show that degradation rate of phenolic wastewater approached to 14.6mg.L-1.h-1.m2-1 when Ti02dosage of 60 mg/L,reaction time of 240 min,Phenolic wastewater initial concentration of 10mg/L and pH5.0.The dosage of TiO2,wastewater initial concentration and pH have significant influence on apparent first-order rate constants of photocatalytic degradation,Reaction kinetics of photocatalytic degradation to phenolic wastewater accordances with the quasi-one grade equation of Langmuir-Hinshelwood.

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45

Lin, Zhaojun, Qianqiong Zhao, Ruilan Fan, Xiaoxue Yuan, and Fuli Tian. "Flame retardancy and thermal properties of rigid polyurethane foam conjugated with a phosphorus–nitrogen halogen-free intumescent flame retardant." Journal of Fire Sciences 38, no. 3 (February 19, 2020): 235–52. http://dx.doi.org/10.1177/0734904119890685.

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In this work, a halogen-free intumescent combining phosphorus and nitrogen, flame-retardant 2-((2-hydroxyphenyl)(phenylamino)methyl5,5-dimethyl-1,3,2-dioxaphosphinane 2-oxide (HAPO) was successfully synthesized. It had been synthesized by reaction of 5,5-dimethyl-1,3, 2-dioxphosphinane 2-oxide with Schiff base. Its chemical structure was characterized in detail by Fourier transform infrared spectroscopy, 1H NMR, and 31P NMR spectrum. The flame-retardant polyurethanes were prepared with different loadings of HAPO. The thermal properties, flame retardancy and combustion behavior of the pure polyurethane foam thermosets were investigated by a series of measurements involving thermogravimetric analysis, limited oxygen index measurement, UL-94 vertical burning test, and cone calorimeter test. The results of the aforementioned tests indicated that HAPO can significantly improve the flame retardancy as well as smoke inhibition performance of polyurethane foam. Compared with the PU-Neat, the limited oxygen index of flame-retardant polyurethanes (15%) thermoset was increased from 19.5% to 23.8% and its UL-94 reached V-0 rating. In addition, the cone test results showed that the heat release rate, total heat release, rate of smoke release, and total smoke production of flame-retardant polyurethanes (10%) were decreased obvious sly. The apparent morphology of carbon residue was characterized by scanning electron microscopy, and results revealed that the modified polyurethane foam can form dense carbon layer after combustion. Thermogravimetric analysis results also indicated that the char amount of flame-retardant polyurethanes was obviously increased compared with PU-Neat. Based on the above analysis, we can draw the conclusions which in the condensed phase, phosphorus-based acids from the degradation of HAPO, this could promote the formation of continuous and dense phosphorus-rich carbon layer. In the gas phase, the flame-retardant mechanism was ascribed to the quenching effect of phosphorus-based radicals and diluting effect by non-flammable gases.

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46

Kosyanchuk, Ludmila, Nataly Kozak, Oksana Antonenko, and Yury Nizelskii. "Reaction kinetics and macromolecule-metal chelate complex formation in metal containing semi-interpenetrating polymer networks based on crosslinked polyurethane and linear polymethylmethacrylate." Chemistry & Chemical Technology 2, no. 4 (December 15, 2008): 263–70. http://dx.doi.org/10.23939/chcht02.04.263.

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According to DSC and EPR data kinetics of formation of simultaneous semi-interpenetrating polymer networks based on crosslinked polyurethane and linear polymethylmethacrylate with 50:50 and 70:30 ratio obtained in the presence of 3d-metal chelates depends on type of metal. On the other hand system composition determines polyurethane or polymethylmethacrylate selection during formation of complexes with metal -diketonates.

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Lu, Zhang, Dan Xia, and Zhen An. "Study on Polyurethane Foam Insulation Materials." Applied Mechanics and Materials 563 (May 2014): 41–47. http://dx.doi.org/10.4028/www.scientific.net/amm.563.41.

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The foaming reaction so that all water-gel reaction and foaming reaction to reach equilibrium, the excellent thermal insulation material was prepared by the regulation of the catalyst, a nucleating agent and an isocyanate. By experiment we know that the amount of stannous octoate catalyst 6%, 4% of the amount of nucleating agent CaCO3, and the case of 100% of the amount of isocyanate, the density of the foam material and the mechanical properties of the insulation material to achieve the best value.

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48

Cho, W. J., H. Park, and J. R. Youn. "Ultrasonic Bubble Nucleation in Reaction Injection Moulding of Polyurethane." Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 208, no. 2 (May 1994): 121–28. http://dx.doi.org/10.1243/pime_proc_1994_208_068_02.

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Ultrasonic foam processing of polyurethane for reaction injection moulding (RIM) was studied experimentally to investigate feasibility of ultrasonic bubble nucleation in polyurethane. Bubble nucleation was also studied theoretically to predict the rate of nucleation. Classical nucleation theory and cluster theory have been employed for explanation of the nucleation phenomena. A polyol resin was saturated with nitrogen at various pressures and the pressure was released slowly in order to generate supersaturated resin. Other components of the selected polyurethane system were added to the supersaturated resin and ultrasonic disruption was applied to the system producing enhanced nucleation. The ultrasonic excitation created a good foam structure even at a low saturation pressure around 0.15 MPa (1.5 atm). The effect of the ultrasonic activation on the bubble nucleation was considered and included in the nucleation theories. The cluster nucleation theory along with consideration of the ultrasonic effect predicted a higher rate of nucleation than the classical nucleation theory for the same condition.

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49

Luo, Yan Ling, Yan Miao, and Feng Xu. "Study on Synthesis and Properties of Novel HTPB/PEG Polyurethane Copolymers." Applied Mechanics and Materials 66-68 (July 2011): 170–73. http://dx.doi.org/10.4028/www.scientific.net/amm.66-68.170.

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Two novel polyurethanes (PU) with alternating and random block architectures, hydroxyl-terminated polybutadiene (HTPB)/polyethylene glycol (PEG) block copolymers, HTPB-alt-PEG and HTPB-co-PEG, were synthesized via a coupling reaction route between hydroxyl groups and isocyanate groups. The structural and crystal characterization was conducted by means of FTIR, and phase behavior was examined by SEM and DSC. The biodegradation in a simulated human body fluid was investigated through mass loss and SEM. The experimental results indicate that all polyurethane samples form the microphase separation structure, and the separation degree depended on their sequence structure and the molecular weight (MW) of PEG, and further affecte their in-vitro degradation.

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50

Ilmiati, Salma, Jana Hafiza, Jaka Fajar Fatriansyah, Elvi Kustiyah, and Mochamad Chalid. "Synthesis and Characterization of Lignin-Based Polyurethane as a Potential Compatibilizer." Indonesian Journal of Chemistry 18, no. 3 (August 30, 2018): 390. http://dx.doi.org/10.22146/ijc.27176.

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Lignin is one of the most abundant biopolymer on earth. It has polar and non-polar side due to its hyperbranched structure, but the polarity of lignin has a higher tendency than non-polarity. Lignin has potential to be compatibilizer if the portion of non-polar can be increased. This research is focused on investigate the synthesis of lignin-based polyurethane to enhance the portion of non-polarity in lignin. Lignin-based polyurethane was prepared by reacting variation 4,4'-Methylenebis(cyclohexyl isocyanate) (HMDI) and polyethylene glycol (PEG), then lignin was added to the reaction. In this study, the structure of lignin-based polyurethane was confirmed by NMR and FTIR. NMR and FTIR showed that lignin successfully grafted. NMR, also used to investigate the variation molar mass of PEG and isocyanate contents effects to polarity of lignin-based polyurethane. The polarity of lignin-based polyurethane decrease as the composition of HMDI and molecular weight of PEG increase. This result also occurs on the sessile drop test that used to determine surface tension of lignin-based polyurethane. The thermal properties of lignin-based polyurethane also investigate using STA. Based on STA, enhancement of composition of HMDI and PEG increase thermal degradation and resistance of lignin-based polyurethane.

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Journal articles on the topic 'Polyurethane reaction'

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