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1
Alsaffar, Eman. "Waterborne polyurethane ionomers : structure-property relationships of elastomeric polyurethane ureas and polyurethane ionomers." Thesis, Loughborough University, 2006. https://dspace.lboro.ac.uk/2134/36047.
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Two groups of water-borne polyurethane ionomers were synthesised using well known methods of synthesis in order to determine the type of elastomers that may be obtained from each method. To begin with, the conventional methods of synthesis for water-borne polyurethane dispersions (WPUDs) in which the process of chain extension occurs in the presence of water was evaluated. This method is restricted to the use of diamines as chain extenders. It was demonstrated that the use of diamines, whether they are primary such as ethylene diamine, or tertiary such as NN'-dimethyl ethylene diamine lead to the formation of polyurethane-urea ionomers that are known for their higher modulus, strength, and lower elongation at break (EAB). The copoly(urethane-urea) ionomers indicated a decreased rate of stress relaxation (RSR). The alternative method of synthesis evaluated was the bulk method of synthesis in which the chain extension process takes place in the bulk. This method allowed the use of diols as chain extenders and resulted in softer elastomers. The polyurethane ionomers obtained by the bulk method of synthesis indicated a high rate of stress relaxation, and, a rapid reduction of load immediately after the application due to their weaker inter-segmental hydrogen bonding interaction.
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Jung, Changdo. "SYNTHESIS OF THERMOPLASTIC POLYURETHANES AND POLYURETHANE NANOCOMPOSITES UNDER CHAOTIC MIXING CONDITIONS." University of Akron / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=akron1124809046.
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Frahn, Stephanie. "Einfluss der Stoffzustände des Quellmittels auf das Quellverhalten von chemisch vernetzten Polymeren in Lösemitteln." [S.l. : s.n.], 1997. http://www.ub.uni-duisburg.de/diss/diss9802/.
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Kohlstrung, Rainer. "Polyurethan-Präpolymere auf der Basis von Sacchariden und Saccharid-Derivaten von der Selektivität zur anwendungstechnischen Prüfung /." [S.l. : s.n.], 2001. http://elib.tu-darmstadt.de/diss/000122.
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Ha, Seung-kyu. "Starch incorporated polymerization of thermoplastic polyurethan." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965659852.
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Bidari, Khosrow. "Investigation of adhesion occurring between polyurethane substrates and polyurethane surface coatings." Thesis, Loughborough University, 1991. https://dspace.lboro.ac.uk/2134/10447.
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Lam, Kit Sang. "Biodegradability of waterborne polyurethane and polyurethane : polyacrylate coating materials in soil /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?CBME%202008%20LAM.
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Jahny, Karsten. "Amphiphile Polyurethan-Makromere als Emulgatoren und Comonomere für die heterophasige Polymerisation hydrophober Monomere." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2002. http://nbn-resolving.de/urn:nbn:de:swb:14-1025614462796-67942.
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Die Arbeit beschreibt die Synthese und Charakterisierung von amphiphilen Polyurethanen mit Emulgatoreigenschaften für die Polymerisation hydrophober Monomere in wässriger Phase. Der Emulgator wurde mit kolloid- und polymerchemischen Methoden hinsichtlich seiner grenzflächenaktiven Eigenschaften sowie einer Strukturbildung in wässriger Phase charakterisiert. Die Emulsionspolymerisation mit dem polymeren PU-Emulgator am Beispiel von Styrol ist untersucht worden. Dabei sind die Partikelgrössen und deren Verteilung in Abhängigkeit von Reaktionsparametern mittels Photonen-Korrelations-Spektroskopie und durch Fluss-Feldfluss-Fraktionierung (F-FFF) bestimmt worden. Weiterhin wurde mittels Dilatometrie und Reaktionskalometrie die Polymerisationskinetik untersucht. Die Partikelmorphologie konnte durch Festkörper-NMR modelliert werden. Durch Atomic Force Microscopy (AFM) im Tapping mode konnte die Oberfläche und die Phasenseparation der polymeren Phasen charakterisiert werdenThis paper describes the synthesis of a reactive amphiphilic polyurethane, and its use as an emulsifier for the emulsion polymerization of styrene. The colloid properties and the structure of the emulsifier in the aqueous phase have been investigated. When the acrylic polymerization is carried out with hydrophobic monomers, we obtain a composite particle structure. The variation of particle size and particle size distribution as a function of the reaction parameters was measured by light scattering methods and Flow-fieldflow-fractionation (F-FFF) . Through investigation by dilatometry and reaction calorimetry it was possible to compare the polymerization process with that of common emulsion polymerization. Solid State NMR analysis allowed us to develop a core-shell model for the composite particle structure, and to determine the presence of an interphase layer between core and shell. Atomic Force Microscopy (AFM) methods were used to characterize the surface of the films, and tapping mode AFM was used to characterize the polymer phase separation on the micro scale
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McLennaghan, A. W. "Linear segmented polyurethane electrolytes." Thesis, University of Strathclyde, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382418.
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Ostrogorsky, Aleksandar G. "Aging of polyurethane foams." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15016.
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Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1986.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING
Bibliography: leaves 151-153.
by Aleksandar G. Ostrogorsky.
Sc.D.
11
Cao, Feina. "Shape Memory Polyurethane Nanocomposites." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1201922381.
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Bryson, John Andrew. "Impact response of polyurethane." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Thesis/Fall2009/j_bryson_082509.pdf.
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Thesis (M.S. in mechanical engineering)--Washington State University, December 2009.Title from PDF title page (viewed on Feb. 11, 2010). "School of Mechanical and Materials Engineering." Includes bibliographical references (p. 93-95).
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Richardson, Tara Beth Auad Maria Lujan Schwartz Peter. "Nanoreinforced shape memory polyurethane." Auburn, Ala., 2009. http://hdl.handle.net/10415/1934.
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Majid, Rohah A. "Polyurethane-polyacrylic hybrid dispersions." Thesis, Loughborough University, 2007. https://dspace.lboro.ac.uk/2134/35337.
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Pure polyurethane dispersions (PUDs) have been synthesised via the prepolymer mixing method, with two different systems i.e. solvent free and the solvent containing PUDs. Isophorone diisocyanate (IPDI), polypropylene glycol (PPG 2000) and dimethylolpropionic acid (DMPA) were the basic materials. The prepolymers were neutralised with triethylamine (TEA) prior to dispersion into the mixture of deionised water and chain extender, hydrazine monohydrate (HYD). The same procedures were repeated in the making of the solvent containing PUDs with 20 wt. % of N-methyl-2-pyrrolidone (NMP). The film properties were examined with Fourier transform infra-red (FT–IR) spectroscopy, stress-strain tests, dynamic mechanical thermal analysis (DMTA), modulated temperature differential scanning calorimetry (MTDSC) and transmission electron microscopy (TEM). The latex particle sizes were measured with a Malvern Zetasizer. It was found that the plasticizing effect of NMP caused reduction in the glass transition temperature, Tg, which also affected the performance of the sample, particularly the tensile strength and extensibility. Annealing the solvent based PUDs under certain conditions improved the properties due to the evaporation of the NMP that was trapped in the films. The solvent-free samples showed superior properties to the solvent-based ones.
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Jahny, Karsten. "Amphiphile Polyurethan-Makromere als Emulgatoren und Comonomere für die heterophasige Polymerisation hydrophober Monomere." Doctoral thesis, Technische Universität Dresden, 2001. https://tud.qucosa.de/id/qucosa%3A24155.
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Die Arbeit beschreibt die Synthese und Charakterisierung von amphiphilen Polyurethanen mit Emulgatoreigenschaften für die Polymerisation hydrophober Monomere in wässriger Phase. Der Emulgator wurde mit kolloid- und polymerchemischen Methoden hinsichtlich seiner grenzflächenaktiven Eigenschaften sowie einer Strukturbildung in wässriger Phase charakterisiert. Die Emulsionspolymerisation mit dem polymeren PU-Emulgator am Beispiel von Styrol ist untersucht worden. Dabei sind die Partikelgrössen und deren Verteilung in Abhängigkeit von Reaktionsparametern mittels Photonen-Korrelations-Spektroskopie und durch Fluss-Feldfluss-Fraktionierung (F-FFF) bestimmt worden. Weiterhin wurde mittels Dilatometrie und Reaktionskalometrie die Polymerisationskinetik untersucht. Die Partikelmorphologie konnte durch Festkörper-NMR modelliert werden. Durch Atomic Force Microscopy (AFM) im Tapping mode konnte die Oberfläche und die Phasenseparation der polymeren Phasen charakterisiert werden.This paper describes the synthesis of a reactive amphiphilic polyurethane, and its use as an emulsifier for the emulsion polymerization of styrene. The colloid properties and the structure of the emulsifier in the aqueous phase have been investigated. When the acrylic polymerization is carried out with hydrophobic monomers, we obtain a composite particle structure. The variation of particle size and particle size distribution as a function of the reaction parameters was measured by light scattering methods and Flow-fieldflow-fractionation (F-FFF) . Through investigation by dilatometry and reaction calorimetry it was possible to compare the polymerization process with that of common emulsion polymerization. Solid State NMR analysis allowed us to develop a core-shell model for the composite particle structure, and to determine the presence of an interphase layer between core and shell. Atomic Force Microscopy (AFM) methods were used to characterize the surface of the films, and tapping mode AFM was used to characterize the polymer phase separation on the micro scale.
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Ren, Hongfeng. "Synthesis and characterization of shape memory poly (epsilon-caprolactone) polyurethane-ureas." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43593.
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A series of segmented poly (epsilon-caprolactone) polyurethane-ureas (PCLUUs) were prepared from poly (epsilon-caprolactone) (PCL) diol, different dissociates and chain extenders to improve the recovery stress of shape memory polymers. NMR and FT-IR were used to identify the structure of the synthesized shape memory polyurethane-ureas. Parameters such as soft segment content (molecular weight and content), chain extender and the rigidity of the main chain were investigated to understand the structure-property relationships of the shape memory polymer systems through DSC, DMA, physical property test, etc. Cyclic thermal mechanic tests were applied to measure the shape memory properties which showed that the recovery stress can be improved above 200% simply by modifying the chain extender. Meanwhile, the synthesis process was optimized to be similar to that of Spandex /LYCRA®. Continuous fibers were made from a wet spinning process, which indicated excellent spinnability of the polymer solution. Small angle neutron scattering (SANS) was used to study the morphology of the hard segment at different temperatures and stretch rates and found that the monodisperse rigid cylinder model fit the SANS data quite well. From the cylinder model, the radius of the cylinder increases with the increasing hard segment content. The SANS results revealed phase separation of hard and soft segments into nano scale domains.
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Kay, Martin John. "Microbial degradation of polyester polyurethane." Thesis, University of Central Lancashire, 1992. http://clok.uclan.ac.uk/20311/.
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During the course of these studies, polyester polyurethane foam has been found to be readily degraded in soil and marine environments. The incorporation of the formulation biocide Vinyzene E.P. reduced the rate and extent of degradation in test material exposed to soil conditions, but was found to be ineffective in preventing degradation when exposed to the marine environment. As a result of these studies, a number of fungi, representing a range of genera, have been isolated, identified, and shown using Kochian principles to degrade polyester polyurethane as a sole source of carbon. A list of isolates is submitted. In addition, a number of bacteria, hitherto unreported as deteriogens of polyester polyurethane, have been isolated and also shown, again using Kochian principles, to degrade polyester polyurethane. In order to effect degradation, the bacteria were found to require supplementation of the basal mineral salts medium with non-defined, complex sources of organic nitrogen, such as yeast extract. Chemical analysis of degraded test material, using FT-IR spectroscopy has provided evidence to suggest that the ester linkage of the polymer was hydrolysed during degradation by a bacterial isolate studied, resulting in marked reductions in the physical properties recorded. No degradation, either in terms of chemical composition or in the physical properties of the polymer was recorded where the test material was inoculated with this isolate in a mineral salts medium supplemented with glucose, suggesting that the enzymes involved in the degradation process were catabolically suppressed and therefore inducible. Extracellular esterase enzyme activity was detected in cellfree supernatants where the mineral salts medium was supplemented with yeast extract, but not in the case where glucose was used. However the addition of the test material did not enhance the level of esterase activity detected. Purification/concentration of these enzymes and characterisation studies using gel filtration chromatography, SDS-PAGE and PAGE were found to support these findings. The results of the present studies suggest that the test material was degraded by the bacterial isolate as a result of co-metabolism.
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Yao, Kejian. "Higher performance polyurethane-organoclay nanocomposites." Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/7795.
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A series of polyurethane (PU)-organoclay nanocompositcs were synthcsised by swelling organically-modified layered silicate (organoclay) in a polyol with subsequent polymerisation. The techniques of wide-angle x-ray diffraction (WAXD), small-angle x-ray scattering (SAXS), transmission electronic microscopy (TEM), scanning electronic microscopy (SEM), Fourier transform infer-red spectroscopy (FTIR), modulated differential scanning calorimetry (MDSQ, contact angle measurement and tensile test were used to investigate the effect of addition of organoclay on curing dynamics, phase structure, tensile properties, dynamical mechanical thermal analysis (DMTA), fatigue durability and surface properties of PUs. FTIR and MDSC revealed that the addition of organoclay has an important influence on curing process of PUs. With increasing organoclay, the reaction between -OH group in polyol and- NCO in isocyanate became fast. WAXD and TEM results showed that PU-organoclay nanocomposites prepared in this research were intercalated materials ones. The addition of organoclay has significant influences on the phase structure of PUs. SAXS results revealed that the long period (average thickness of soft and hard segment) decreased with increasing organoclay. Contact angle measurements showed that the organoclay can affect the surface properties of PU nanocomposites. The addition of organoclay resulted in the decrease in surface energy. AFM results revealed that the adhesion force of the surface of PU nanocomposites decreased with increasing organoclay. Tensile strength and elongation of PUs at break were improved significantly by incorporating organoclay. The tensile strength increased up to 100%, and elongation increased up to 120%. At high soft segment content, with increasing organoclay, the modulus decreased slightly, and at low soft segment content, the modulus increased with increasing organoclay. The addition of organoclay improved significantly thermal stability of PUs. Fatigue measurements uggestedt hat the fatigue durability can significantly be improved by incorporating organoclay. A nanospring concept for understanding the enhancemenht as been proposed.
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Wilson, D. "Polyurethane-polymethyl methacrylate graft copolymers." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47306.
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Charalambides, Yiannis C. "Isocyanate precursors for polyurethane synthesis." Thesis, University of Cambridge, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615169.
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Seboa, Sharrief. "Polyurethane dispersions for paper coatings." Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/53005.
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Thesis (MSc)--Stellenbosch University, 2002.ENGLISH ABSTRACT: Aqueous polyurethane (PU) dispersions were synthesized for the use in paper coatings. These PUs contained a polyester polyol soft segment (content of 60-70%) and a urethane hard segment (content of 30-40%). This was followed by grafting using four different grafting agents. Triethylamine (TEA) was used as the neutralizing agent. The polyester polyol segment consisted of neopentyl glycol (NPG), adipic acid, 1,4-cyclohexane dicarboxylic acid (1,4-CHOCA) and 2-phosphonobutane-1 ,2,4- tricarboxylic acid (PSTCA), while the urethane hard segment consisted of hydrogenated 4,4-diphenylmethane diisocyanate, dimethylolproponic acid (OMPA), 3-hydroxypivalic acid (HPA) and hydroxyethylene methacrylate (HEMA). The grafting agents used were lauryl methacrylate (LMA), n-butyl methacrylate (n-SMA), methyl methacrylate (MMA) and styrene. Two different polyester polyols were synthesized, one containing 10% phosphate and the other none. The polyols were characterized in terms of their acid value, hydroxyl value and molecular mass. The PUs synthesized from the polyol containing 0% phosphate were grafted with LMA, while the phosphate-containing PUs were grafted with each of the all four grafting agents. The resulting dispersions were applied to paperboard, and then dried at a maximum temperature of 100°C. The PU-coated paperboard was characterized using the moisture vapour transmission rate (MVTR), and scanning electron microscopy (SEM) techniques. PU films (not supported by paper, stand alone) were prepared by heating the PU dispersion in Teflon holders up to 130°C for 6 hours. The dried films were then characterized by thermogravimatric analysis (TGA), differential scanning calorimetry (OSC), dynamic mechanical analysis (OMA) and Fourier transform infrared spectroscopy (FTIR). MVTR-analysis showed that the phosphated PU coatings had a minimum MVTR-value at 0% grafting, and that its overall MVTR-values were much lower than that of the non-phosphated PU coatings. SEM-analysis showed that the phosphated PU coatings had no pinholes at a maximum of 8% grafting, while the non-phosphated PU coatings showed pinholes at all levels of grafting. OMA-analysis showed that the phosphated PU samples had higher Tg's (Tg onset between O-S°C)than that of the non-phosphated PU samples (Tgonset below -SO°C).
AFRIKAANSE OPSOMMING: POLI-URETAAN DISPERSIES VIR PAPIER BEDEKKINGS Waterige poli-uretaan (PU) dispersies is gesintetiseer vir gebruik as papierbedekkings. Hierdie poli-uretane het 'n poliester poli-ol sagte segment (60-70% inhoud) en 'n uretaan harde segment (30-40% inhoud) bevat. Die poli-uretane is met vier verskillende ent-middels geêent. Trietielamien (TEA) is as neutraliseermiddel gebruik. Die poli-ester poli-ot segment het bestaan uit: neopentielglikol (NPG), adipiensuur, 1,4-sikloheksaandikarboksielssuur (1,4- SHDKS) en 2-fosfonobutaan-1 ,2,4-trikarboksielssuur (FSTKS). Die uretaan harde segment het bestaan uit: hidrogeneerde 4,4-difenielmetaandiisosianaat, dimetielpropioonsuur (DMPS), 3-hidroksipivaalsuur (HPS) en hidroksietileenmetakrilaat (HEMA). Laurielmetakrilaat (LMA), n-butielmetakrilaat (n-SMA), metielmetakrilaat (MMA) en stireen is as entmiddels gebruik. Twee verskillende poli-ester polihidroksie verbindings is gesintetiseer: een met 10% fosfaat en een met geen fosfaat, en gekarakteriseer in terme van hulle suurwaardes, hidroksiwaardes en molekulêre massas. Die PUs wat vanaf die fosfaat-bevattende poli-ol gesintetiseer is, is met LMA geêent, terwyl die fosfaat-bevattende PUs met al vier entmiddels geêent is. Papier (Eng. paperboard) is met hierdie dispersies bedek en by 100°C gedroog. Die PU-bedekte papier is gekarakteriseer in terme van vogdeurlaatbaarheidstransmissie (Eng: MVTR - the moisture vapour transmission rate), en skandeerelektonmikroskopie (SEM). PU-films wat nie deur papier gestut is nie is ook voorberei deur die verhitting van die PU dispersies in Teflon houers (130°C, 6 ure). Die droë films is daarna gekarakteriseer deur middel van termogravimetriese analise (TGA), differensiêle skandeerkalorimetrie (DSC), dinamiese meganiese analise (OMA) en Fourier-transformasie infrarooispektroskopie (FTIR). Resultate van MVTR analises het getoon dat die fosfaat-bevattende PU bedekkings 'n mimimum MVTR-waarde by 0% enting gehad het, en dat die totale MVTR waardes baie laer was as die van die nie-fosfaatbevattende bedekkings. SEM het gewys dat die fosfaat-PU bedekkings by 8% enting geen mikrogaatjies (Eng. pinholes) gehad net nie, terwyl die PU bedekings met geen fosfaat mikrogaatjies (Eng. pinholes) by alle vlakke van enting gehad het. OMA analises het getoon dat die monsters van die fosfaatbevattende PU hoër Tg waardes gehad het (Tg begin tussen 0 en 5 "C) as die nie-fosfaatbevattende PU monsters (Tg begin onder -50°C).
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Pavlova, Ewa. "Hyperbranched polyesters for polyurethane coatings: their preparation, structure and crosslinking with polyisocyanates." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2007. http://nbn-resolving.de/urn:nbn:de:swb:14-1172267166280-42303.
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In this work, hyperbranched aromatic polyesters-polyphenols based on 4,4-bis(4’ hydroxy¬phenyl)pentanoic acid (BHPPA) were prepared and, according to the authors knowledge, for the first time tested as precursors for polyurethane bulk resins and coatings. Comparison of poly-BHPPA with competing products The materials prepared in this work show better properties than their aliphatic polyester-polyol analoga based on 2,2-bis-(hydroxymethyl)propanoic acid (BHMPA). Especially, the solubility of poly-BHPPA in organic solvents is better and poly-BHPPAs also do not tend to microphase separation during their reaction with isocyanates, in contrast to poly-BHMPAs. The poly-BHPPA and the polyurethane networks made from them display higher Tg values than analogous poly- BHMPA compounds. Because of the high Tg of the reacting and final systems, curing must occur at elevated temperatures (90°C) in order to avoid undercure. The lower reactivity of phenolic OH groups prevents the reaction from being too fast at that temperature. A drawback of the polyurethanes based on the aromatic polyesters-polyols prepared is the lower thermal stability of their urethane bonds, if compared to aliphatic urethanes. An interesting possibility for future investigations would be the modification of the BHPPA monomer in order to change the OH functionality from phenolic to aliphatic OH, e.g. by replacement of the phenolic OH by hydroxymethyl or hydroxyethyl groups (requires a strong modification of the monomer synthesis) or simpler by reacting the phenolic OH of BHPPA with a suitable reagent like oxirane, which would lead to groups like O-CH2-CH2-OH in the place of the phenolic OH. Such a BHPPA modification should in turn yield modified “poly-BHPPA” polycondensates, which would combine the advantages of poly-BHPPA with those of aliphatic OH precursors of polyurethanes. Poly-BHPPA synthesis Hyperbranched polymers of the 4,4-bis-(4’-hydroxyphenyl)pentanoic acid (BHPPA) were synthesized successfully by the catalyzed (by dibutyltin diacetate) polycondensation of BHPPA. The products obtained were oligomers with number average molecular weight ranging from 1800 to 3400 g/mol (polymerization degree of ca. 6 to 12), displaying a first moment of functionality in the range 7 to 14. Such products were good OH precursors for the preparation of polyurethane coatings, because higher functional polymers would gel at low conversions. The analysis of the functional groups (determination of acid and hydroxyl numbers) and the 1H-NMR and the 13C-NMR spectroscopy were found to be good methods for the determination of molecular weights. The polydispersity of the poly-BHPPA products was in the range 3.5 to 6. Their degree of branching was found to be in the range 0.36 to 0.47. Poly-BHPPA containing aliphatic polyols as core monomers were also prepared successfully. Difunctional and trifunctional core monomers usually reached a full conversion of their OH groups, while the tetra- and hexafunctional core monomers were converted only to 89%. In all these products however, a considerable amount, usually even a majority, of the polymer molecules were core free. The poly-BHPPA products prepared displayed relatively high glass transition temperatures, in the range of 84°C to 114°C, obviously due to interactions between the phenol groups and to hydrogen bridging. The thermal stability of these products was also high, with decomposition occurring near 350°C (at a heating rate of 10°C / min) Kinetics investigations of the poly-BHPPA reactivity towards isocyanates The poly-BHPPA are polyphenols and were expectedly found to react significantly slower with isocyanates than aliphatic alcohols. The reactivity of poly BHPPA was also found to be somewhat lower than that of the monofunctional, low molar-mass 4 ethylphenol. Hexamethylene diisocyanate trimer, Desmodur N3300, was found to be more reactive than hexamethylene diisocyanate (HDI) or butyl isocyanate in all experiments, possibly due to a substitution effect. The substitution effect can be explained by a change of microenvironment caused by conversion of isocyanate group and OH group into urethane groups. The reactions of low-molecular-mass alcohols or phenols with low molecular weight isocyanates followed well the 2nd order kinetics, while the reactions of poly-BHPPA with isocyanates show deviations from ideal 2nd order kinetics at higher conversions. All the kinetics experiments were carried out under catalysis by dibutyltin dilaurate. This catalyst inhibits the undesired reaction of isocyanate groups with moisture. It was also found that the catalysis was necessary to reach reasonable curing times for poly-BHPPA based polyurethane networks. The uncatalyzed systems reacted extremely slowly. Preparation of polyurethane networks from poly-BHPPA The poly BHPPA products prepared were used successfully as OH functional precursors of polyurethane networks. The networks prepared contained only very low sol fractions. Acetone and also ethylene diglycol dimethylether (diglyme) were found to be good swelling solvents for the networks prepared, while methyl propyl ketone was a much poorer solvent and aromatic compounds like toluene or xylene practically did not swell the poly BHPPA based polyurethanes. The networks prepared contain a relatively high amount of cyclic bonds, 40 to 50% in the finally cured state, which is an expected result for systems with precursors of high functionality and with small distances between the functional groups. The temperature of glass transition (Tg) of the networks prepared (ranging from 68°C to 126°C) depends of the poly BHPPA precursor used: it increases with increasing molecular mass and with increasing core functionality. The choice of the isocyanate crosslinker also influences Tg: the networks made from HDI show higher Tg values, than networks made from the same poly BHPPA but crosslinked with Desmodur N3300 (Tri HDI). The urethane bonds in the networks prepared start to decompose near 140°C. The easier degradation of PU with aromatic urethane bonds is a disadvantage in comparison with aliphatic polyurethanes, whose decomposition starts at 200°C. The surfaces of polyurethane coatings prepared are smooth, displaying a roughness of ca. 20-25 nm, and relatively hydrophilic: the contact angle with water was found to be near 80°. The prepared networks are also relatively hard, possessing the Shore D hardness of 70.
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Chauveau, Cyril. "Non-isocyanate polyurethanes, polyamides and silyl modified polymers synthesized by olefin metathesis : alternative solutions to polyurethane adhesives." Thesis, Rennes 1, 2018. http://www.theses.fr/2018REN1S127.
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Les polyuréthanes (PUs) sont utilisés comme adhésifs depuis des décennies, mais l’utilisation d’isocyanates durant leur synthèse les place aujourd’hui dans la visée de nouvelles réglementations. Dans ces travaux, nous décrivons trois technologies alternatives potentielles aux Pus, basés sur la métathèse d’oléfines. La première technologie repose sur la synthèse de polyuréthanes sans isocyanates (NIPUs) à partir de motifs carbonate de vinylène (VC). Des polyoléfines VC2-téléchéliques ont été synthétisées par polymérisation par ouverture de cycle par métathèse / métathèse croisée (ROMP/CM) de cyclooléfines en présence d’un agent de transfert (CTA) de type VC. Cependant, la polyaddition avec une diamine a mis en évidence des reactions secondaires empêchant d’obtenir le matériaux désiré. La seconde technologie considérée est la synthèse de polyamides (PA). Des polyoléfines diazlactone (AZL)2-téléchéliques ont été synthétisées par ROMP/CM en presence d’un CTA de type AZL, puis ouvertes par une diamine. Des PAs ont ainsi été obtenus avec succès, mais en faibles quantités, ne permettant pas d’étudier leurs propriétés mécaniques ou adhésives. La dernière approche utilise les polymères silylés (SMPs). Trois types de SMPs ont été synthétisés par diverses stratégies de métathèse : des polypropylèneglycols (PPGs), des copolymères polycyclooctène (PCOE)/PPG et des copolymères polybutadiène (PBD)/PPG. La polycondensation de ces SMPs par différents systèmes catalytiques a été étudiée, ainsi que les propriétés mécaniques et adhésives des matériaux résultants. Parmi ceux-ci, les copolymères PCOE/PPG SMPs ont démontré de remarquables propriétés mécaniques et adhésives, meilleures que la plupart des SMPs commerciaux d’aujourd’huiPolyurethanes (PUs) have been used as adhesives for decades, but the toxic isocyanates needed for their synthesis is now on the scope of regulations. In this work, we describe three potential alternative technologies to classic PUs, based on a powerful polymerization tool: olefin metathesis. The first technology relies on the synthesis of nonisocyanate polyurethanes from vinylene carbonate (VC) functionalities. Telechelic VC polyolefins were synthesized by ring-opening metathesis polymerization/cross-metathesis (ROMP/CM) of cycloolefins with a VC chain-transfer agent (CTA). However, polyaddition attempts with a diamine evidenced side-reactions, preventing the isolation of the expected material The second technology considered is the synthesis of polyamide (PA). Following a similar strategy, telechelic azlactone (AZL) polyolefins were synthesized by ROMP/CM of cycloolefins with an AZL CTA, then, were subsequently opened by a diamine. PA were successfully obtained through this strategy, however in small quantities, thus, no mechanical nor adhesive tests were carried out. The last technology uses silyl modified polymers (SMPs). Three type of SMPs were synthesized, using diverse olefin metathesis strategies : polypropylene (PPG), polycylooctene (PCOE)/PPG copolymers and polybutadiene (PBD)/PPG copolymers. Curing of the trimethoxysilyl or triethoxysilyl groups inside these SMPs was studied using different catalytic systems, as well as the mechanical and adhesive properties of the materials obtained. Among them, PCOE/PPG copolymers displayed remarkable good mechanical and adhesive properties, better than the majority of commercial SMPs available today
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Wirts, Martin. "Emission von Isocyanaten bei der Verarbeitung von Polyurethanklebstoffen." [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=960356304.
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Campbell, Kayleen Theresa. "The structure of segmented polyurethane nanocomposites /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18982.pdf.
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Fong, Nicole Wei Shi Graduate School of Biomedical Engineering Faculty of Engineering UNSW. "Antibacterial polyurethane nanocomposites for urinary devices." Publisher:University of New South Wales. Graduate School of Biomedical Engineering, 2009. http://handle.unsw.edu.au/1959.4/43627.
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Hospital-acquired infections are a significant contributor to clinically-related morbidity and mortality. The majority of these infections are associated with the use of invasive medical devices, where urinary catheters account for ~36% of cases. Current preventative strategies have shown short-term (<7 days) success, however their long-term (>28 days) efficacy is unclear. This thesis explores the use of solution-cast polyurethane nanocomposite (PUNC) materials for antimicrobial drug delivery in urinary applications. It is hypothesised that the enhanced barrier properties of PUNCs, afforded by the incorporation of well-dispersed nanoinclusions, would allow for the sustained release of an antimicrobial agent. The objectives of this research were to investigate the antibacterial, mechanical and barrier properties of PUNCs incorporating various silicates modified using antimicrobials, hypothesised to also act as dispersing agents. Organically modified silicates (OMS) were prepared at 110%, 200% and 300% cationic exchange capacity (CEC) using the biocide, chlorhexidine diacetate (CHX), which was hypothesised to perform the dual functions; dispersant and antibacterial agent. Resulting OMS were incorporated at 1wt% and 5wt% loadings into a PU matrix to produce PUNCs; PEU-CHX1.1MMT, PEU-CHX2.0MMT, and PEU-CHX3.0MMT, respectively. CHX performed well as a dispersant, producing intercalated to partially exfoliated PUNCS. Antibacterial activity was dependent on OMS type and loading. PEU-CHX1.1MMT materials had poor antibacterial properties, but the addition of free CHX into the materials significantly improved their efficacy, demonstrating long-term sterility in an in vitro urinary tract (UT) model. PEU-CHX2.0MMT and PEU-CHX3.0MMT at 5wt% OMS loadings had partially exfoliated structures and excellent antibacterial activity. Cytotoxicity was evident in all materials, although to a lesser extent in the latter. Overall, intermediate OMS loadings of CHX2.0MMT would be expected to produce PUNCs with favourable antibacterial activity and cytocompatibility. PUNC drug-release profiles demonstrated sustained release compared to pristine PU, indicative of enhanced barrier properties. Their ultimate tensile properties decreased with increased OMS loading or addition of free CHX.Higher cationic-exchanged OMS caused significant reductions in strain. Young's modulus increased in response to higher %CEC OMS and loading. PUNCs show promise as antibacterial biomaterials for long-term urinary applications, where antimicrobial release and mechanical properties can be modulated through organic modification and OMS loading.
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Verhoeven, Vincent Wilhelmus Andreas. "The reactive extrusion of thermoplastic polyurethane." [S.l. : [Groningen : s.n.] ; University Library Groningen] [Host], 2006. http://irs.ub.rug.nl/ppn/292374224.
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Meade, Lorne E. "Effective elastic modulus of polyurethane asperities." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/15990.
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Williams, Paul. "New metal catalysts for polyurethane formation." Thesis, University of Warwick, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392935.
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Mao, Jianwen. "Polyurethane microgels and controlled drug delivery." Thesis, University of Strathclyde, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263035.
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Williams, Jonathan Mark. "Mechanical behaviour of flexible polyurethane foams." Thesis, University of Leicester, 1995. http://hdl.handle.net/2381/34725.
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Dunlop Suspensions and Components manufacture microvon, a flexible polyurethane foam, which is used extensively in the automotive industry as spring aids for car suspension systems. The material is used because of its desirable non-linear elastic stress/stain characteristics, its quick recovery behaviour, and because it tends to produce little lateral expansion during compression. The design of such spring aid components, however, remains something of a black art, since the behaviour of the material is not fully understood. Complications arise because the mechanical properties of the material are controlled by a large number of physical, chemical and processing effects. The aim of the research has been to gain further understanding of the material, and its response under load, in order to be able to predict the compressive behaviour of the material. This has been achieved by combining microstructural observations of the deforming material with information obtained from detailed mechanical tests. There have been many attempts by researchers to describe the behaviour of cellular materials. This has been done in a variety of ways, and approaches have included developing complicated strain energy functions or utilising simple models based on repeating cell units. However, a number of difficulties are encountered when applying these material models to microvon. The microstructural observations and mechanical tests undertaken in this research have led to the development of new material models for cellular materials. Two types of model have been developed; a physical model and a series of phenomenological models. The physical model is a bi-linear relationship between stress, strain and density, in which the mechanisms of deformation are described. The phenomenological models have been developed using curve- fitting, to accurately predict the axial stress/strain and lateral/axial strain behaviour of microvon over a wide range of strain, density, temperature and strain rate.
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Mead, Joey Lou. "Mechanical degradation of a polyurethane elastomer." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15174.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1986.MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE
Bibliography: leaves 121-126.
by Joey Lou Mead.
Ph.D.
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Folz, Diane C. "Variable Frequency Microwave Curing of Polyurethane." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/34567.
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Historically, coatings were processed from natural oils, fats, and resins; the first well-known and widely used being lacquer [Meir-Westhues, 2007]. In the 20th century, synthetic resins were developed to achieve coatings with improved properties. Of these coating compositions, polyurethanes (PURs) were one of the most prevalent. Polyurethanes became possible in 1937 when Otto Bayer developed the diisocyanate polyaddition process [Randall et al, 2002]. Since that time, literally thousands of PUR compositions have been used commercially. The primary application of interest in this study is that of coatings for wood substrates.
It is well-known among materials researchers that there can be a number of differences between microwave and conventional materials treatment techniques [Clark et al, 1996], including enhanced reaction rates, lowered processing temperatures for some products, and selective interactions in composite systems.
The primary goals of this research were to determine (1) whether microwave energy affected the cure rate in a water-based, aliphatic PUR, and (2) if there was an effect of microwave frequency on the cure rate.
The primary tool for determining extent of cure in the PUR samples was Fourier transform infrared spectroscopy (FTIR). Using this characterization method, the changes in intensities of four bonds specific to the PUR composition were followed. It was determined that, in the particular PUR composition studied, microwave energy had an effect on the cure rate when compared with conventional heating, and that there was a frequency effect on the cure rate. Additionally, a deeper understanding of the use of FTIR spectroscopy techniques for studying cure kinetics was developed.Master of Science
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Erden, Numan. "Polyurethane-Polybenzoxazine Based Shape Memory Polymers." University of Akron / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=akron1259000268.
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Rohm, Kristen Nicole. "Thermoplastic Polyurethane: A Complex Composite System." Case Western Reserve University School of Graduate Studies / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=case1625604511143102.
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Almeida, Hugo Filipe Delgado. "Electrospun polyurethane biomembranes for vascular grafts." Master's thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/22589.
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Mestrado em Materiais e Dispositivos BiomédicosUm dos grandes desafios da engenharia de tecidos (TE) vasculares, prende-se com a pouca disponibilidade de tecidos vasculares autólogos para substituição de vasos sanguíneos de pequeno diâmetro (<6 mm). Estudos demonstram que o poliuretano possui propriedades mecânicas adequadas para a utilização em vasos sanguíneos de pequenos diâmetros. Trabalhos anteriores realçam as propriedades antibacterianas de compósitos compostos por PU e nanopartículas de oxido de zinco (nZnO). O presente estudo teve como objetivo a produção de membranas compósitas de PU/ nZnO com recurso a electrofiação. Mais concretamente pretendia-se avaliar as propriedades antibacterianas e mecânicas dos compósitos, testando diferentes concentrações de nZnO. Foram sintetizadas nanopartículas de óxido de zinco, através do método de precipitação química à temperatura ambiente, obtendo-se nano estruturas porosas. As membranas compósitas foram testadas contra E.coli e S.aureus evidenciando um bom comportamento antibacteriano, bem como uma relação do mesmo com a concentração de nZnO nas membranas. No que diz respeito aos ensaios mecânicos, as membranas mostraram boas propriedades. Em conclusão, as nZnO podem ser adicionas ao PU formando uma membrana com propriedades antibacterianas e boas propriedades mecânicas
One of the great challenges of vascular tissue engineering (TE) is the lack of availability of autologous vascular tissues to replace small-diameter (<6 mm) blood vessels. Studies have shown that polyurethane has mechanical properties suitable for use in blood vessels of small diameters. Previous papers highlight the antibacterial properties of composites composed of PU and nanoparticles of zinc oxide (nZnO). The present study had as objective the production of composite membranes of PU / nZnO with the use of electrofying. More specifically, it was intended to evaluate the antibacterial and mechanical properties of the composites by testing different concentrations of nZnO. Nanoparticles of zinc oxide were synthesized through the chemical precipitation method at room temperature, obtaining nano porous structures. The composite membranes were tested against E. coli and S. aureus showing a good antibacterial behavior, as well as a relation thereof with the concentration of nZnO in the membranes. With regard to mechanical tests, the membranes showed good properties. In conclusion, the nZnO can be added to the PU forming a membrane with antibacterial properties and good mechanical properties.
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Zafar, Urooj. "Biodegradation of polyurethane under composting conditions." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/biodegradation-of-polyurethane-under-composting-conditions(0157c580-bffe-4b2f-a019-a7510fa3ac4e).html.
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Plastic are a highly durable, lightweight and low cost family of polymeric materials that form an essential and integral component of today’s world. Their continued world-wide large scale manufacture has led them to be a major component of man-made waste. A large proportion of plastic waste is directed to the landfill sites, however their low degradation rates, scarcity of landfill sites and growing water and land pollution problems require alternatives to be developed. Composting is a natural process involving aerobic decomposition of organic wastes by a mixed microbial consortium that involves thermophilic microbes during the process due to the heat generated during decomposition. In this study we investigated the biodegradation of polyurethane under composting conditions. Polyurethanes are heteropolymers with a wide range of applications in the medical, automotive, construction and domestic field and in Europe account for 7% of all plastic manufacture and have been shown to be susceptible to biodegradation, particularly by fungi. In this thesis, it was found that loss in tensile strength of >70% occurs at both mesophilic (25°C) and thermophilic (45° and 50°C) temperatures under laboratory conditions and so is susceptible to degradation at all stages of the composting process. Moreover, polyester PU buried in compost piles at a commercial composting site during the maturation phase of an in silo composting process also underwent substantial degradation. Non-culture based analysis by TRFLP, DGGE and 454 pyrosequencing revealed that the fungal communities colonising the surface of PU was substantially different from the surrounding compost indicating selection of fungi on the PU surface. Pyrosequencing revealed that under laboratory conditions, at 25°C Fusarium solani, and 45°C and 50°C, Candida ethanolica was the dominant organism recovered from the PU surface, whereas at the commercial composting site an unidentified fungal clone and Arthrographis kalrae were the dominant organisms recovered. When the microparticulate polyester PU dispersion impranil was added to compost, a substantial shift in the indigenous fungal population was observed along with an increase in fungal viable numbers, however, addition of larger solid PU had no lasting effect on the surrounding compost community. This study demonstrates that polyester PU is highly susceptible to degradation in during composting and indicates a future potential for directing PU wastes to existing commercial composting processes.
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Pope, Ellen Grace. "Sepiolite/polyurethane open cell foam composites." Thesis, University of Bristol, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.738272.
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Pitkänen, M. (Mika). "Biochar/polyurethane composites:mechanical and electrical properties." Master's thesis, University of Oulu, 2019. http://jultika.oulu.fi/Record/nbnfioulu-201908082751.
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Abstract. As non-renewable resources are being depleted, legislative regulations are tightening and environmental awareness is increasing, the interest in using more environment-friendly materials is growing. In particular, there is higher demand for alternative options to petroleum-based materials, such as polymers and composites. However, in order to replace these materials with bio-based options, their quality should be the same as or better than petroleum-based materials. It is known that the properties of bio-based materials and additives are highly affected by the feedstock and its processing conditions. Biochar is a viable option for use as an additive in polymers to create electrically conductive polymer composites. For example, there is interest in developing conductive polyurethane composites to be used as an abrasion-resistant material in industry. The use of biochar would also decrease the amounts of petroleum-based additives used in the field. Moreover, the raw material options for biochar are abundant.
The main objective of this study was to study whether it is possible to prepare electrically conductive composite materials by incorporating biochar (BC) in polyurethane (PU). Another aim was to study how the addition of biochar would affect the wear and hardness properties of polyurethane. For the first part of the thesis, a literature survey was conducted focusing on electrically conductive polyurethane composites and the type of additives used in them. The focus was to gather information about the carbon and biochar additives used and their properties. In the experimental part, biochar based on different wood species was ground to smaller particle sizes (300–700 nm), and these biochar powders were mixed with polyurethane and then cast into sheets for further characterization. The dielectric, wear, and hardness properties of the prepared PU/BC composites were studied as well as the dispersion of the biochar in the polyurethane matrix and the interface between the biochar and PU.
The results show that PU-BC composites have good wear properties and hardness values, which were only slightly lower than those of neat PU. However, electrical percolation was not achieved even with the highest amounts of BC. Biochar had the greatest effect on the electrical properties as it was found to be non-conductive due to the low pyrolysis temperature as well as the high void content in the composites. The results show that biochar should be of higher quality to be able to conduct electrical current. Nevertheless, good adhesion between additive and matrix was achieved in the composites according to microscopy images. In future work, more focus should be placed on improving the electrical conductivity of biochar in order to achieve composites suitable for electrical applications.Polyuretaani/biohiili komposiitien mekaaniset ja sähköiset ominaisuudet. Tiivistelmä. Rajalliset luonnonvarat, tiukentuvat lainsäädännöt sekä ympäristötietoisuuden lisääntyminen lisäävät kiinnostusta ympäristöystävällisten materiaalien käytöstä. Erityisesti vaihtoehtoja muovin ja komposiittien valmistuksessa käytetylle raakaöljylle etsitään kovasti. Mikäli raakaöljy halutaan korvata biopohjaisella raaka-aineella, tulee sen täyttää vaaditut ominaisuudet. On yleisesti tiedossa, että biopohjaisiin materiaaleihin ja lisäaineiden ominaisuuksiin vaikuttaa suuresti raaka-aineet ja prosessointi olosuhteet. Yksi mahdollinen vaihtoehto, jossa biopohjaisia täyteaineita voitaisiin käyttää, ovat sähköä johtavat biohiilikomposiitit. Sähköä johtavia polyuretaanikomposiitteja voidaan käyttää esimerkiksi sellaisissa teollisuuden käyttötarkoituksissa, jossa vaaditaan kulutuksenkestävyyttä. Tämä auttaisi vähentämään raakaöljypohjaisten täyteaineiden käyttöä tällä alalla. Biohiilen raaka-ainetta on yleisesti hyvin saatavilla joka puolella maailmaa.
Tämän työn päätavoitteena oli tutkia voiko polyuretaanista ja biohiilestä valmistaa sähköä johtavia komposiitteja. Toinen työn tavoite oli tutkia kuinka biohiili vaikuttaa polyuretaanin kulutuksen kestoon ja kovuuteen. Ensimmäinen osio tässä työssä on kirjallisuuskatsaus, jossa keskitytiin sähköä johtaviin komposiitteihin, sekä niissä käytettyihin täyteaineisiin. Kirjallisuusosiossa keskityttiin keräämään tietoa käytössä olevista hiili, ja biohiili täyteainesta sekä niiden ominaisuuksista. Työn kokeellisessa osiossa eri puulajeista valmistetut biohiilet jauhettiin 300–700nm partikkelikokoon, sekoitettiin polyuretaaniin ja valettiin polyuretaani-biohiilikomposiitti levyiksi. Valmistettujen komposiittien kulutuksen kestoa ja kovuutta, kuten myös sähköisiä ominaisuuksia tutkittiin mittaamalla dielektrisiä ominaisuuksia komposiiteista. Koska hyvän dispersion saaminen komposiittien valmistuksessa on haastavaa, tutkittiin komposiittien mikrorakennetta ja polyuretaanin/biohiilen vuorovaikutusta kenttäemissiopyyhkäisy-elektronimikroskoopilla.
Tulokset osoittavat, että tehdyillä polyuretaani/biohiili komposiiteilla on hyvät kulutuksenkesto ja kovuus ominaisuudet, nämä ominaisuudet huononivat vain hieman alkuperäisistä arvoista, mutta sähköistä perkolaatiota ei saavutettu edes korkeimmilla biohiilipitoisuuksilla (15 m%). Syynä huonoihin elektronisiin ominaisuuksiin on huonolaatuinen, sähköä johtamaton biohiili ja suuri huokoisuus. Nämä ominaisuudet johtuvat biohiilen valmistuksessa käytetystä lämpötilasta. Mikroskooppikuvat komposiittien rakenteesta osoittavat, että polyuretaanin ja biohiilen adheesio on hyvä mutta kaikissa komposiiteissa on suuri huokoisuus, joka vaikuttaa komposiittien ominaisuuksiin negatiivisesti. Tulevissa tutkimuksissa tulisi keskittyä biohiilen sähköisten ominaisuuksien parantamiseen sekä huokoisuuden estämiseen.
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Pavlova, Ewa. "Hyperbranched polyesters for polyurethane coatings: their preparation, structure and crosslinking with polyisocyanates." Doctoral thesis, Technische Universität Dresden, 2006. https://tud.qucosa.de/id/qucosa%3A24962.
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In this work, hyperbranched aromatic polyesters-polyphenols based on 4,4-bis(4’ hydroxy¬phenyl)pentanoic acid (BHPPA) were prepared and, according to the authors knowledge, for the first time tested as precursors for polyurethane bulk resins and coatings. Comparison of poly-BHPPA with competing products The materials prepared in this work show better properties than their aliphatic polyester-polyol analoga based on 2,2-bis-(hydroxymethyl)propanoic acid (BHMPA). Especially, the solubility of poly-BHPPA in organic solvents is better and poly-BHPPAs also do not tend to microphase separation during their reaction with isocyanates, in contrast to poly-BHMPAs. The poly-BHPPA and the polyurethane networks made from them display higher Tg values than analogous poly- BHMPA compounds. Because of the high Tg of the reacting and final systems, curing must occur at elevated temperatures (90°C) in order to avoid undercure. The lower reactivity of phenolic OH groups prevents the reaction from being too fast at that temperature. A drawback of the polyurethanes based on the aromatic polyesters-polyols prepared is the lower thermal stability of their urethane bonds, if compared to aliphatic urethanes. An interesting possibility for future investigations would be the modification of the BHPPA monomer in order to change the OH functionality from phenolic to aliphatic OH, e.g. by replacement of the phenolic OH by hydroxymethyl or hydroxyethyl groups (requires a strong modification of the monomer synthesis) or simpler by reacting the phenolic OH of BHPPA with a suitable reagent like oxirane, which would lead to groups like O-CH2-CH2-OH in the place of the phenolic OH. Such a BHPPA modification should in turn yield modified “poly-BHPPA” polycondensates, which would combine the advantages of poly-BHPPA with those of aliphatic OH precursors of polyurethanes. Poly-BHPPA synthesis Hyperbranched polymers of the 4,4-bis-(4’-hydroxyphenyl)pentanoic acid (BHPPA) were synthesized successfully by the catalyzed (by dibutyltin diacetate) polycondensation of BHPPA. The products obtained were oligomers with number average molecular weight ranging from 1800 to 3400 g/mol (polymerization degree of ca. 6 to 12), displaying a first moment of functionality in the range 7 to 14. Such products were good OH precursors for the preparation of polyurethane coatings, because higher functional polymers would gel at low conversions. The analysis of the functional groups (determination of acid and hydroxyl numbers) and the 1H-NMR and the 13C-NMR spectroscopy were found to be good methods for the determination of molecular weights. The polydispersity of the poly-BHPPA products was in the range 3.5 to 6. Their degree of branching was found to be in the range 0.36 to 0.47. Poly-BHPPA containing aliphatic polyols as core monomers were also prepared successfully. Difunctional and trifunctional core monomers usually reached a full conversion of their OH groups, while the tetra- and hexafunctional core monomers were converted only to 89%. In all these products however, a considerable amount, usually even a majority, of the polymer molecules were core free. The poly-BHPPA products prepared displayed relatively high glass transition temperatures, in the range of 84°C to 114°C, obviously due to interactions between the phenol groups and to hydrogen bridging. The thermal stability of these products was also high, with decomposition occurring near 350°C (at a heating rate of 10°C / min) Kinetics investigations of the poly-BHPPA reactivity towards isocyanates The poly-BHPPA are polyphenols and were expectedly found to react significantly slower with isocyanates than aliphatic alcohols. The reactivity of poly BHPPA was also found to be somewhat lower than that of the monofunctional, low molar-mass 4 ethylphenol. Hexamethylene diisocyanate trimer, Desmodur N3300, was found to be more reactive than hexamethylene diisocyanate (HDI) or butyl isocyanate in all experiments, possibly due to a substitution effect. The substitution effect can be explained by a change of microenvironment caused by conversion of isocyanate group and OH group into urethane groups. The reactions of low-molecular-mass alcohols or phenols with low molecular weight isocyanates followed well the 2nd order kinetics, while the reactions of poly-BHPPA with isocyanates show deviations from ideal 2nd order kinetics at higher conversions. All the kinetics experiments were carried out under catalysis by dibutyltin dilaurate. This catalyst inhibits the undesired reaction of isocyanate groups with moisture. It was also found that the catalysis was necessary to reach reasonable curing times for poly-BHPPA based polyurethane networks. The uncatalyzed systems reacted extremely slowly. Preparation of polyurethane networks from poly-BHPPA The poly BHPPA products prepared were used successfully as OH functional precursors of polyurethane networks. The networks prepared contained only very low sol fractions. Acetone and also ethylene diglycol dimethylether (diglyme) were found to be good swelling solvents for the networks prepared, while methyl propyl ketone was a much poorer solvent and aromatic compounds like toluene or xylene practically did not swell the poly BHPPA based polyurethanes. The networks prepared contain a relatively high amount of cyclic bonds, 40 to 50% in the finally cured state, which is an expected result for systems with precursors of high functionality and with small distances between the functional groups. The temperature of glass transition (Tg) of the networks prepared (ranging from 68°C to 126°C) depends of the poly BHPPA precursor used: it increases with increasing molecular mass and with increasing core functionality. The choice of the isocyanate crosslinker also influences Tg: the networks made from HDI show higher Tg values, than networks made from the same poly BHPPA but crosslinked with Desmodur N3300 (Tri HDI). The urethane bonds in the networks prepared start to decompose near 140°C. The easier degradation of PU with aromatic urethane bonds is a disadvantage in comparison with aliphatic polyurethanes, whose decomposition starts at 200°C. The surfaces of polyurethane coatings prepared are smooth, displaying a roughness of ca. 20-25 nm, and relatively hydrophilic: the contact angle with water was found to be near 80°. The prepared networks are also relatively hard, possessing the Shore D hardness of 70.
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Wang, Shanshan. "Development of solid polymer electrolytes of polyurethane and polyether-modified polysiloxane blends with lithium salts." Akron, OH : University of Akron, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1196139638.
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Dissertation (Ph. D.)--University of Akron, Dept. of Polymer Engineering, 2007."December, 2007." Title from electronic dissertation title page (viewed 01/30/2008) Advisor, Kyonsuku Min; Committee members, Mark Soucek, Kevin A. Cavicchi, Gary R. Hamed, Michael H. Cheung; Department Chair, Sadhan C. Jana; Dean of the College, Stephen Z. D. Cheng; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
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Li, Yang. "Application of cellulose nanowhisker and lignin in preparation of rigid polyurethane nanocomposite foams." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44746.
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Cellulose nanowhisker (CNW) prepared by acid hydrolysis of softwood Kraft pulp was incorporated as nanofiller in rigid polyurethane (PU) foam synthesis. The density, morphology, chemical structure, mechanical properties and thermal behavior of the products were characterized. The nanocomposites exhibited better performance especially at high CNW¡¯s content which was probably due to the high specific strength and aspect ratio of CNW, the hydrogen bonding and crosslinking between CNW and polymer matrix, a higher crosslinking density compared to the control, and the function of CNW as an insulator and mass transfer insulator. Lignin polyol was synthesized through oxypropylation and used for rigid PU foam preparation. The density, morphology, chemical structure, compressive property and thermal behavior of the product were characterized. Lingin-based rigid PU foam showed improved compressive property compared to its commercial counterpart. Ethanol organosolv lignin-based PU showed a slightly stronger compressive property than Kraft lignin-based PU. The enhancement was primarily attributed to the rigid phenolic structure and the high hydroxyl functionality of lignin. Lignin-based PU generated more char than common PUs which was possibly related to the better flame retardant property. This study provided an alternative way to valorize the two most abundant biopolymers and resulted in relatively environmentally benign rigid PU nanocomposite foam.
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Woo, Tim. "Rigid polyurethane nanocomposites : understanding structure-property relationships /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18708.pdf.
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Cristiano, Antonella. "Fracture by cavitation of model polyurethane elastomers." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2009. http://pastel.archives-ouvertes.fr/pastel-00578499.
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L'objectif principal de cette thèse a été de déterminer le rôle joué par l'architecture macromoléculaire du réseau sur les propriétés élastiques non linéaires, la résistance à la rupture et la résistance à la cavitation sous chargement hydrostatique. Nous avons synthétisé, dans des conditions contrôlées, trois réseaux élastomères dits « modèles » de Polyuréthanne (PU), à partir d'un triisocyanate et de polyether diols isomoléculaires (PPG). Une caractérisation physico-chimique fine des réactifs et des réseaux a été réalisée en utilisant des techniques telles que : RMN, FTIR et fractions solubles. Les propriétés élastiques non linéaires, viscoélastiques linéaires et la résistance à la rupture en mode I des trois réseaux modèles ont été caractérisées. Les essais de cavitation ont été effectués sur un dispositif expérimental développé pour cette étude, permettant de suivre les mécanismes de formation de cavités, à la résolution optique près, en temps réel. En menant une analyse systématique des conditions de cavitation, en fonction de la vitesse de déformation et de la température, il est apparu que, contrairement au modèle d'instabilité élastique communément utilisé, l'expansion critique de la cavité n'est pas uniquement pilotée par le module élastique; mais dépend fortement de l'énergie de rupture, GC et de l'extensibilité limite du réseau. Par ailleurs, nous avons observé l'apparition de cavités pré-critiques avant la fracture catastrophique ; ce qui met en évidence l'existence de deux critères : l'un, propre au processus de nucléation, principalement piloté par des mécanismes statistiques et activés thermiquement (distribution de défauts, temps, température, etc.) ; et l'autre, lié à la croissance de la cavité en milieu confiné contrôlé par GIC, et par le comportement aux grandes déformations. Enfin, la présence d'enchevêtrements dans l'architecture du réseau macromoléculaire s'est avérée clairement bénéfique pour stabiliser la croissance de cavités et donc pour renforcer la résistance à la cavitation.
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Theiss, Timothy J. "Preliminary investigation into the cracking of polyurethane." Thesis, This resource online, 1987. http://scholar.lib.vt.edu/theses/available/etd-04122010-083619/.
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Seboa, Sharrief. "Synthesis and characterization of tailored polyurethane coatings." Thesis, Link to the online version, 2005. http://hdl.handle.net/10019/1197.
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Saw, Lin K. "Phase inversion in polyurethane prepolymer-water dispersions." Thesis, Loughborough University, 2000. https://dspace.lboro.ac.uk/2134/15350.
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Aqueous polyuethane (PU) colloids, like many other water-borne polymer colloids, have become an increasingly important class of materials in the surface coating industry. Three processing stages, the pre-dispersion, dispersion and postdispersion stages, are generally involved in the production of aqueous PU colloids. However, existing researches have neglected the importance of the dispersion stage. The present study aims to develop better understanding of the dispersion stage during the production of aqueous PU colloids. Non chain-extendable PU pre-polymer (PUp) is used to enable independent study of the dispersion stage and the phase inversion process is chosen due to its widespread industrial usage. Valid drop size characterisation techniques and phase inversion detection methods have been developed in this project. Three different dispersion regions have also been identified by changing the ionic group content of PUp. Each dispersion region is associated with a particular dispersion type. Those are (I) Stable aqueous emulsions that contain small PUp-in-water drops. They were produced using PUp with more than 0.2 mmole/g of ionic groups. (2) Aqueous PUp colloids with 0.05 ~ 0.2 mmole/g of ionic groups. These emulsions contain a mixture of drop structures, including simple drops and different multiple drops. (3) Aqueous PUp dispersions containing less than 0.05 mmole/g of ionic groups. These dispersions are not stable and the resultant dispersions separated when agitation was stopped. Modified phase inversion maps are introduced to represent the occurrence of all three dispersion regions. The modified phase inversion maps are partly analogous to those of conventional non-ionic-surfactant-water (nSOW) systems. The three dispersion regions have also been "reproduced" successfully using external surfactants as substitutes for the internal stabilising groups. A new catastrophic phase inversion mechanism is proposed to explain the existence of all three dispersion regions. Other variables studied during this project include different neutralising agents. different amount of carboxylic acid groups, operating temperatures and material addition rates. In conclusion, this project shows that the phase inversion process is a feasible route for producing aqueous polymer dispersions with little or no added external surfactants. Stable PUp-W dispersions can also be produced below the minimum ionic group content reported in existing literatures.
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Pain, Christopher Charles. "Finite element simulations of polyurethane foaming processes." Thesis, University of Exeter, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303744.
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Zafar, Shazia. "Investigation of small molecules from polyurethane materials." Thesis, De Montfort University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398240.
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Shuttleworth, W. A. "Biodegradation of polycaprolactone polyurethane by Gliocladium roseum." Thesis, Cranfield University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.380772.
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