Dissertations / Theses on the topic 'Polyurethanes'
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1
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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Goodby, Amanda. "Biodegradable thermoplastic polyurethanes." Thesis, Aston University, 2015. http://publications.aston.ac.uk/32134/.
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The overall aim of this work was to investigate the biodegradability of a number of polyurethane elastomers synthesised by different methods and targeted for a specific agricultural purpose in which the polyurethane was required to be degradable in soil after its useful life. Polyurethanes were synthesised commercially using two different methods; a ‘one-shot’ method where all of the reactants were added simultaneously, and a ‘pre-polymer’ method, in which the isocyanate and polyol were reacted together before addition of the chain extender. The effect of the method of synthesis on the rate of degradation and biodegradation was investigated using accelerated alkaline hydrolysis, enzymatic hydrolysis and soil burial, where it was found that the polyurethane synthesised by the ‘pre-polymer’ method hydrolysed faster under alkaline conditions (21 days) than that synthesised by the ‘one-shot’ method (56 days). This was found to be due to differences in the polymer morphology, with an increase in microcrystalline domains occurring during the ‘one-shot’ process. The effect of the chemical constituents of the synthesised polyurethanes on the rate of degradation and biodegradation were also investigated. Comparison of polyurethanes synthesised with an aliphatic (H12MDI) and an aromatic isocyanate (MDI) resulted in an increase in the rate of alkaline hydrolysis with the use of H12MDI. This was found to be affected mainly by differences in the morphology, with an increase in microphase separation and a decrease in microcrystalline regions in the case of the use of H12MDI Polyurethanes were synthesised using different polyols; PEA, PCL, PEG and PCL/PEG (50:50) to investigate the effect of the polyol on the rate of biodegradation, where it was found that the polyurethane containing a combination of the two polyols, PCL/PEG (50:50), degraded under both accelerated hydrolysis conditions and soil burial. This was thought to be due to the combination of both hydrophilic (PEG) and hydrophobic (PCL) charactyers of the polyols, which had contributed to increasing the diffusion of water into the polymer matrix (hydrophilic PEG), and also to inducing the microbial degradation by hydrophobic interactions (PCL). The incorporation of the additives; iron stearate, cellulose and Cloisite 30B were examined as a means of increasing the degradation and biodegradation of the polyurethane polymers. Addition of iron stearate was found to decrease the thermal stability of the polyurethane, which resulted in an increase in polyurethane degradation under alkaline conditions at 45oC, and biodegradation under soil burial conditions at 50oC. The incorporation of cellulose into the polyurethane increased the rate of alkaline hydrolysis and biodegradation in soil. This polyurethane (PU CE) was also susceptible towards enzymatic degradation by Aspergillus niger. The incorporation of the organically-modified nanoclay Cloisite 30B has decreased the microcrystalline domain structure contained within the polyurethane, and this was found to decrease the rate of alkaline hydrolysis dramatically (degraded within 7 days).
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Coote, Alexander Stuart. "Polyurethanes for enzyme immobilisation." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47386.
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Xu, Tong. "UV-Curable Hybrid Polyurethanes." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1406471515.
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Williams, L. K. "Polyurethanes from renewable resources." Thesis, University of Sheffield, 2013. http://etheses.whiterose.ac.uk/4358/.
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A series of polyurethane (PU) and polyurethane-urea (PUU) elastomers derived from a renewable source have been synthesised and characterised extensively. Comparisons have been made to analogous series of elastomers utilising petroleum derived diisocyanates. The renewable elastomers utilised a difuranic diisocyanate (DFDI) derived from furfural, a readily available raw material synthesised from agricultural waste. DFDI was synthesised using a modified version of a published procedure, utilising triphosgene for the formation of the diisocyanate. The reaction kinetics of the diisocyanates used were compared using an adiabatic temperature rise technique in both catalysed and uncatalysed reactions, showing that DFDI reacts at approximately one fifteenth the rate of MDI with primary alcohols. The polyurethane series comprised MDI/DFDI and 1,4-butanediol (BD) hard segments (HS) and polytetrahydrofuran (PTHF) soft segments (SS) at 1, 2 and 2.9 kDa molecular weights. The PUU series utilised the 2kDa PTHF SS and the amine precursor to the diisocyanate, in effect simulating the HS produced in a water blown (polyurethane-urea) foam. In all PU elastomers the DFDI variants displayed much greater degrees of phase separation as evidenced by lower soft segment (SS) Tgs observed by both DSC and DMTA measurements, greater invariants observed in SAXS frames, more SS crystallinity observed in WAXS data and a much more clearly defined morphology observed in tapping mode AFM images. Crystallinity within the SS was found to be much higher in DFDI based elastomers, whereas crystalline hard segments were only observed in MDI based PU elastomers and was more pronounced at higher HS contents and at lower SS molecular weights. The PUU elastomers showed very clear morphologies in AFM images but were found to possess a lower degree of phase separation overall, agreeing with previous literature suggesting that the stronger hydrogen bonding of urea groups can hinder phase separation.
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Panesar, Satwinder Singh. "Mould release layers for polyurethanes." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38131.
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Peng, Chao. "Cationic Polyurethanes for Antimicrobial Applications." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1542383983590224.
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Freij-Larsson, Christina. "Surface modification of biomedical polyurethanes." Lund : Dept. of Chemical Engineering II, Lund University, 1996. http://catalog.hathitrust.org/api/volumes/oclc/38985470.html.
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Porter, Stephen Christopher. "Synthesis, surface characterization, and biointeraction studies of low-surface energy side-chain polyetherurethanes /." Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/9845.
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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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Ahmad, Zeeshan. "Synthesis and Novel Processing of Polyurethanes." Thesis, Queen Mary, University of London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485558.
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Polymeric materials have been'' used in a variety of biomedical applications. Although some polymeric materials are more biocompatible than others, there are always some degree of interaction between the material and the host environment. These interactions depend on how the polymers are synthesised and fabricated playing a major role in predicting their long-term behaviour. These factors are directly related to morphological and chemical structUre of these i:.! materials. This study focuses on a class of polymeric material, polyurethanes, and then to prepare a novel materi~l through novel. synthesis routes and electro-spinning, fOf fabricating porous structures from polyurethanes. . A selection of Polyurethanes were synthesised using the two step solvent polymerisation methods without the use, of a catalyst, as catalysts can cause premature degradation of the polymeric chain and act as fungicides· within the biological environment. Characterisation was performed using· Fourier Transform Infrared (FT-IR), Fourier Transform Raman (FTRaman)/ Raman, Differential Scanning Calorimetry (DSC) and Gel Permeation Chromatography (GPC). Degradation profile of the polymers was assessed through simple hydrolytic degradation and tensile properties ofthe materials were also evaluated. A scaffold material was obtained by using Agar as a soft segment, as their hydrolysis ratio can be vaned by changing the hard and soft segments of the resulting polyurethane. Agar has a number of hydroxyl groups within its structure and provides sufficient reaction sites for the isocyanate to react and form urethane linkages. The ratios of reactants were varied and the reaction conditions optimised. A series of co-polymers were also synthesised with Agar molecule. A selection of the polymers prepared from the first section was electrospun to form scaffolds. Prior to electrospinning, polymers were assessed for pH, relative permittivity, viscosity, surface tension, conductivity and density to ascertain the properties of polymers that are required for the electrospinning proces.s. Highly. porous polymeric scaffold materials were obtained, which were analysed under the optical microscope and the scanning electron microscope (SEM).
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Zhang, Changhong. "Elastic degradable polyurethanes for biomedical applications." Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1219848181/.
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Lam, Kwok Hing. "Some unsaturated, grafted and ionic polyurethanes." Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47529.
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Blackwell, Catherine Jayne. "Synthesis and degradation of biodegradable polyurethanes." Thesis, Durham University, 2017. http://etheses.dur.ac.uk/11961/.
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A series of biodegradable star poly(ε-caprolactone) (PCL)-based polyols and PCL-based diisocyanate prepolymers were synthesised and fully characterised. Biodegradable polyurethanes (PUs) were synthesised using star PCL-based polyols and either biodegradable diisocyanate prepolymers 4,4’-methylenebis(phenyl isocyanate) (MDI) or 2,4-toluene diisocyanate (TDI). The resulting polyols, diisocyanate prepolymers and PUs were subjected to enzymatic degradation using lipase for up to 30 days. Chapter 1 is a general introduction to the reactions involved in the syntheses of PU foams and the ring-opening polymerisation of cyclic esters. The general components used in PU formulations including biodegradable polyols and diisocyanate prepolymers are discussed. Furthermore, polymer biodegradation testing methods and analytical methods to monitor degradation are investigated. Chapter 2 includes the syntheses and enzymatic degradation of a series of biodegradable four- and six-arm star PCL polyols. This was achieved through the tin(II)octoate (SnOct2) catalysed ring opening polymerisation (ROP) reaction of ε-caprolactone (ε-CL) using pentaerythritol, di(trimethylolpropane) and dipentaerythritol initiators. Furthermore, a series of six-arm star poly[(ε-caprolactone)-co-(β-butyrolactone)] were synthesised in a similar manner. Star PCL and star poly[(ε-CL)-co-(β-BL)] both exhibited almost 100% mass loss after 15 days of enzymatic degradation at a constant rate. Generally, an initial increase in % crystallinity (%χc) is seen for star PCL and star poly(ε-CL)-co-(β-BL) in the first few days (0-3 days) of enzymatic degradation. This was followed by a decrease in crystallinity (%χc), indicating amorphous regions of the polymer were preferentially degraded. This was supported by scanning electron microscopy (SEM) analyses showing surface pitting and occurrence of crystal spherulite structures within the first few days of enzymatic degradation. Chapter 3 concerns the synthesis and enzymatic degradation of a series novel four-arm dumbbell-shaped copolymers (PCL)2-(PEG)-(PCL)2 bridged with 2,2’-bis(hydroxymethyl)propionic acid (bisMPA) moieties. This was achieved by the synthesis of a tetra-hydroxyl PEG macro-initiator through a coupling reaction of poly(ethylene glycol) (PEG) and acetyl-protected bisMPA using dicyclocarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP). Subsequently, the four-arm star structure was synthesised with the SnOct2 catalysed ROP of ε-CL using tetra-hydroxyl PEG macroinitiator. Contact angle and %water uptake (%WU) indicated the copolymers containing a higher %PEG showed increased hydrophilic nature and surface wetting. A dispersity (Ð) of 1.32-1.51 and a small molecular weight shoulder were seen due to using a polydisperse PEG macro-initiator and the high viscosity of the reaction mixture under bulk conditions. The novel star copolymers showed >90% mass loss within 7 days and an increase in %χc within the first few days of enzymatic degradation. Chapter 4 entails the synthesis and enzymatic degradation of biodegradable seven arm star PCL with a central acetylated β-cyclodextrin (β-CD) moiety. This was achieved through a four step synthetic route involving the protection of 1° OH groups on the β-CD moiety, acetylation of the 2° OH groups on the β-CD moiety, removal of protecting group on the 1° OH group and subsequent ROP of ε-CL catalysed by SnOct2. Contact angle and %WU analyses showed minimal surface wetting and high hydrophobicity. A very low rate of enzymatic degradation was seen with 7% mass loss and a general increase in %χc in 20 days. Chapter 5 involves the synthesis and enzymatic degradation of a series of biodegradable diisocyanate prepolymers containing a central PCL or PCL-b-PEG-b-PCL moiety and capped with either MDI or TDI moieties. This was achieved through the reaction of two molar equivalents of the diisocyanate moiety, MDI or TDI, and either PCL diol or PCL-PEG-PCL triblock copolymer. The diisocyanate prepolymers showed absorbances attributing to the C=N stretch in the NCO group as well as N-H and C-N in the urethane group in FT-IR spectra. Contact angle and %WU measurements of diisocyanate prepolymers with higher %PEG showed increased surface wetting and hydrophilicity. Generally the TDI-based diisocyanate prepolymer showing 100% mass loss in 4 days, degraded at a faster rate than MDI-based diisocyanate prepolymer of 23% in 40 days. Furthermore, the lower Mn MDI-based prepolymer showed a significantly faster rate of enzymatic degradation of 79% mass loss in 40 days than the higher Mn MDI-based prepolymer. Chapter 6 concerns the synthesis and enzymatic degradation of a series of biodegradable PUs using biodegradable PCL-based star polyols and diisocyanate prepolymer components synthesised in Chapter 2-5. PU gels were produced as a result of a minimal amount of dichloromethane (DCM) solvent to ensure complete mixing. Generally, PUs showed the disappearance of the C=N stretch in fourier transform infrared spectroscopy (FT-IR) analyses, indicating all NCO groups successfully reacted to give urethane groups. PUs showed up to 18.5% mass loss over the 30 days of enzymatic degradation. Comparisons of the PU degradation behaviour were made to demonstrate the effects of polyol type, diisocyanate type, and ratio of NCO:OH used, on the rate of PU enzymatic degradation. Chapter 7 surmises and concludes the work covered in Chapter 2-6 and suggests further work.
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Khan, Imran. "Environment-induced changes in biomedical polyurethanes." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620709.
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Toffey, Ackah. "Cure studies of network-forming polyurethanes." Thesis, Virginia Tech, 1993. http://hdl.handle.net/10919/41509.
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The polyhydroxy character of lignocellulosics and their natural abundance make them good candidates for the manufacture of polyurethanes.
The cure characteristics of hydroxypropyl-cellulose and hydroxypropyl lignin (HPC and HPL, respectively) with polymeric methylene diphenyl diisocyanate (MDI) was studied via dynamic mechanical thermal analysis (DMTA).
HPC/MDI and HPL/MDI resins flow at 30°C and proceed to cure at 50°C. The latter has excellent thermal stability over the former. Crosslinking of HPL and HPC with MDI follow an nth order kinetics, with an order of reaction of 2 and an apparent activation energy in the range of 12.9 kcal/mol - 14.7 kcal/mol.
The rate of cure with time is higher in HPL-based polymers than HPC-based ones at the initial stage of cure; the difference vanishes at later stages. This demonstrates that the hydroxyl groups in HPC are less accessible to the NCO groups, and that cure rate might be dependent on diffusion limitations at later stages.
Degree of cure, under all cure schedules, follows a parallel trend, and has to do with the fact that the hydroxyl groups of HPC are less accessible to isocyanate. Both HPL and HPC react with MDI at a reduced rate in comparison to a synthetic polyol: caprolactone triol.
Time-glass transition temperature superposition was used to calculate times to vitrification of the HPL-based polymers, and is presented in a TTT cure diagram. This bio-based polymer displays the s-shaped vitrification pattern characteristics of thermosets. A similar approach did not work with HPC-based polymers. HPC- and HPL-based polymers did not display damping transitions, in isothermal cure, typical of gelation and vitrification. As the isocyanate to hydroxyl ratio (NCO:OH) increased, the glass transition temperature of the polymers increased, and the transition amplitude and width decreased and increased, respectively.
In practical terms, this study illustrates that it is advantageous to use
a) to use high isocyanate to hydroxyl ratios in order to produce polyurethanes which retain desirable damping behavior over a wider range of temperature.
b) to use HPC/MDI resins in those situations where retention of stiffness at temperatures below 230° is required.
c) to use HPL where rapid cure is desired.
The study also reveals that the relative reactivity of water, HPL and HPC with isocyanate takes the form water > HPL > HPC.Master of Science
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Mace, Tamara Lee. "Phase segregation study of thermoplastic polyurethanes." Diss., Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04072004-180051/unrestricted/mace%5ftamara%5fl%5f200312%5fms.pdf.
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Wu, Yuguang. "Protein and platelet interactions with polyurethanes /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/8027.
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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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Río, Nieto Enrique del. "New polyurethanes from vegetable oil-based polyols." Doctoral thesis, Universitat Rovira i Virgili, 2011. http://hdl.handle.net/10803/31904.
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Los poliuretanos son uno de los materiales poliméricos más usados debido a sus buenas propiedades. Tradicionalmente, los poliuretanos se han sintetizado a partir de derivados del petróleo, sin embargo, teniendo en cuenta motivos de sostenibilidad, se hace necesario desarrollar tecnologías más ecológicas y económicamente viables.
En esta tesis se han obtenido poliuretanos con buenas propiedades mecánicas y memoria de forma a partir de polioles basados en aceites vegetales, utilizando diferentes estrategias sintéticas: A partir de oleato de metilo epoxidado, mediante polimerización por apertura de anillo y posterior reducción; por polimerización vía metátesis de monómeros derivados de aceite de ricino y mediante polimerización por apertura de anillo de oxazolinas derivadas de ácidos grasos y posterior funcionalización vía acoplamiento tiol-eno con mercaptoetanolPolyurethanes are one of the most important polymeric materials, and exhibit versatile properties suitable for use in many fields. However, the synthesis of polyurethanes from renewable resources is still an important challenge for scientists. In the search for green routes for polyurethanes, fats and oils offer important alternatives for the production of polyols, thus enable substitute petrochemicals. In this thesis, polyurethanes with good mechanical and shape-memory properties have been synthesized. Three different ways have been exploited to obtain polyols from vegetable oil derivatives: Polyols obtained by ring opening polymerization of epoxidized methyl oleate and reduction of the ester groups. Two different families of polyols have been synthesized by metathesis polymerization of castor oil-based monomers. Polyoxazoline-polyols were achieved by ring opening polymerization of fatty acid-based oxazolines and functionalization of the obtained polyoxazolines by thiol-ene coupling with mercaptoethanol.
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Guney, Aysun. "Composition-property Relationship Of Pcl Based Polyurethanes." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614253/index.pdf.
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The desirable properties of polyurethanes (PUs) such as mechanical flexibility
associated with chemical versatility make these polymers attractive in the
development of biomedical devices. In this study, various segmented
polyurethanes were synthesized through polymerization reactions between
polycaprolactone (PCL) diol or triol and excess hexamethylene diisocyanate
(HDI) with varying NCO/OH ratios and the effect of composition on the
properties of the resultant polyurethane films were examined. Initially, isocyanate
terminated prepolymers were synthesized through one-shot polymerization, and
then these prepolymers were cured by introducing crosslinkages into the structure
and thus PUs were obtained. In order to enhance biocompatibility and
hydrophilicity of the resulting polymers, heparin was added into the prepolymer before the curing process. The influence of excess HDI as a crosslinker on the
degree of H-bond formation between hard-hard segments or hard-soft segments
was examined by using Fourier transform infrared-Attenuated total reflectance
spectroscopy (FTIR-ATR). Also the effects of HDI content on the chemical,
physical and mechanical properties of the polyurethanes were examined with
differential scanning calorimetry (DSC), X-Ray diffraction spectroscopy (XRD),
dynamic mechanical analyzer (DMA), mechanical tester and goniometer. FTIR-
ATR, DSC and DMA analyses showed that use of triol resulted in better network
formation and homogenous distribution of hard segments within soft segment
matrix. Incorporation of heparin into the polymer matrix produced more
hydrophilic films (water contact angle reduced from 80 to 60). Polyurethanes
from PCL and HDI in the absence of any solvent, initiator, catalyst or chain
extender were successfully synthesized and this kind of synthesis enhanced
biocompatibility and increased the potential of polymers for use in biomedical
applications.
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Lenz, Emma. "Ultrasonically assisted preparation of polyurethanes and polylactones." Thesis, University of Bath, 1995. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760683.
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Wei, Manqing. "Synthesis of Precursors to Non-isocyanate Polyurethanes." Thesis, North Dakota State University, 2018. https://hdl.handle.net/10365/29167.
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Biobased diamines are excellent precursors for the synthesis of non-isocyanate polyurethanes (NIPUs). We have prepared several biobased diamines using three different reactions for their synthesis. In the first method, we have carried out chain elongation of cellulose-derived 2,5-diformylfuran by the Henry reaction followed by reduction of the nitroalkene. Yields of the key step: Hantzsch Ester reduction, were 70-80%. Method two involves the Friedel-Crafts alkylation of furfurylamine with different ketones under acidic conditions. Yields of large-scale alkylation reaction were 60-77%. In method three, we combined the Henry reaction and Friedel-Crafts alkylation techniques to access diamines from hemicellulose-derived furfural. These diamines can be reacted with carbonates to access hydroxyalkylcarbamates in good yields, around 80%. We have also developed a novel method for accessing biscarbamates directly from dialdehydes in good yields, 70-94%. The hydroxyalkylcarbamates and biscarbamates are valuable precursors to obtain polyurethanes via the phosgene-free route.
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Bo, Chong. "Nanohybrids Based on Solid and Foam Polyurethanes." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc799520/.
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Polymer nanocomposites are a going part of Materials Science and Engineering. These new composite materials exhibit dimensional and thermal stability of inorganic materials and toughness and dielectric properties of polymers. Development of nanocomposites become an important approach to create high-performance composite materials. In this study silica, fly ash, silica nanotubes and carbon black particles have been added to modify polyurethane foam and thermoplastic polyurethanes. It has been found that the addition of silica can diminish the size of foam bubbles, resulting in an increased stiffness of the material, increase of the compressive strength, and greater resistance to deformation. However, the uniformity of bubbles is reduced, resulting in increased friction of the material. Fly ash added to the foam can make bubbles smaller and improve uniformity of cells. Therefore, the material stiffness and compressive strength, resistance to deformation, and has little impact on the dynamic friction of the material. Adding nanotubes make bubble size unequal, and the arrangement of the bubble uneven, resulting in decreased strength of the material, while the friction increases. After the addition of carbon black to the polyurethane foam, due to the special surface structure of the carbon black, the foam generates more bubbles during the foaming process changing the foam structure. Therefore, the material becomes soft, we obtain a flexible polyurethane foam. The results of mechanical properties determination of the thermoplastic polyurethane that adding particles may increase the stiffness and wear resistance of the thermoplastic polyurethane, while the tensile properties of the material are reduced. This phenomenon may be due to agglomeration of particles during the mixing process. Possibly the particles cannot be uniformly dispersed in the thermoplastic polyurethane.
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Zhang, Lizhong. "Physical, mechanical, thermal, and viscoelastic properties of water-blown rigid polyurethane foam containing soy flours /." free to MU campus, to others for purchase, 1998. http://wwwlib.umi.com/cr/mo/fullcit?p9924871.
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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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Lunn, Matthew D. G. "Development and application of well-defined titanium alkoxide pre-catalysts." Thesis, University of Bath, 2002. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.250846.
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Nabeth, Bruno. "Relations entre la structure et les proprietés de polyurethanes et polyurethanes acrylates. : Application vernis : : protection des cartes à puces." Lyon, INSA, 1994. http://www.theses.fr/1994ISAL0075.
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Le travail présenté concerne l'étude des propriétés de réseaux polyuréthanes (PU) et polyuréthanes acrylates (PUA) de natures chimiques voisines. Une étude préliminaire des températures de transition vitreuses de copolymères linéaires modèles a tout d'abord été entreprise. Les variations de Tg des deux types de réseaux PU et PUA ont ensuite été décrites en fonction de la composition chimique (pourcentage de segments souples, masses molaires moyenne entre nœuds et concentration en liaisons uréthane). Les hétérogénéités d'ordre statistique dans les réseaux thermodynamiquement homogènes ont permis de décrire les variations de Tg et des propriétés viscoélastiques en introduisant la notion d'agrégat. Les agrégats sont des zones rigides de fonctionnalité élevée constituées par des nœuds rigides connectés. La théorie des cascades permet de modéliser la formation de ces agrégats, de calculer leur fonctionnalité et leur éventuelle percolation. Les PUA dilués dans un solvant réactif polymérisés sous ultra-violet ont ensuite été caractérisés. Nous avons montré l'influence de la fonctionnalité et de la nature chimique du solvant réactif sur les propriétés. L'application vernis imprimable a permis de dégager une relation entre propriétés et imprimabilitéThe aim of this work is to study the influence of the chemical structure on the properties of polyurethane (PU) and acrylate polyurethane (PUA) networks. The variation of Tg with the type of macrodiol, its length and the chemical composition of the polymer were studied in relation with the percentage of soft segments, the molar mass between cross-links and the concentration of urethane bonds. Glass transition temperature, Tg, dynamic mechanical relaxation and equilibrium modulus, E' were measured to compare the two kinds of networks. To explain thermal and mechanical properties of networks, the concept of hard cluster crosslinks, which are represented by structures of chemically linked "hard" units: diisocyanate linked to TMP in the case of PU networks, and microgel-like polymerized polyacrylate chains in the case of PUA networks, has been introduced. The Branching theory can model the formation, the functionalities and the percolation of the clusters. PUA networks UV-polymerized are characterized with a constant dilution level to study the importance of the reactive diluent composition (chemical structure and unctionalities) on the properties. Concerning the printing application, a relation between the thermal and mechanical properties and printing is observed
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González, Paz Rodolfo Jesús. "Polyurethanes based on fatty acids with improved biocompatibility." Doctoral thesis, Universitat Rovira i Virgili, 2012. http://hdl.handle.net/10803/96663.
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El objetivo principal de esta tesis ha sido el desarrollo de nuevos poliuretanos a partir de ácidos grasos como fuentes renovables, utilizando química “click” en la síntesis de los dioles y polioles correspondientes. La primera parte del trabajo describe la preparación de los monómeros “vía” acoplamiento tiol-eno ó tiol-ino, su caracterización y las propiedades de los poliuretanos sintetizados. Como los polímeros a partir de ácidos grasos provienen de macromoléculas biológicas y pueden ser potencialmente biocompatibles, la segunda parte del trabajo está dirigida a incrementar la biocompatibilidad de los poliuretanos a través de diversas estrategias de funcionalización con moléculas bioactivas, para su implementación en ingeniería de tejidos. Tres metodologías fueron investigadas: mezclas con gelatina; inmovilización covalente de colágeno sobre la superficie mediante plasma; e inmovilización iónica de sulfato de condroitina sobre la superficie mediante aminólisis.The main objective of this thesis has been the development of new polyurethanes from renewable sources such as fatty acids, using "click" chemistry in the synthesis of the corresponding diols and polyols. The first part of this study describes the preparation of monomers "via" thiol-ene or thiol-yne coupling, characterization and properties of the synthesized polyurethanes. As the polymers from fatty acids derived from biological macromolecules and can be potentially biocompatible, the second part of this work is focused on the enhancement of polyurethanes biocompatibility through bioactive molecules functionalization strategies, for tissue engineering purposes. Three approaches have been investigated: blends of polyurethanes and gelatin; covalent surface modification of polyurethanes with collagen by plasma treatment; and ionic surface modification of polyurethanes with chondroitin sulfate by aminolysis treatment.
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Theron, Jacobus Petrus. "Development of crosslinkable, thermoplastic polyurethanes for cardiovascular prostheses." Thesis, Link to the online version, 2006. http://hdl.handle.net/10019.1/1315.
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Segura-Velandia, Diana M. "A case-based reasoning methodology to formulating polyurethanes." Thesis, Loughborough University, 2006. https://dspace.lboro.ac.uk/2134/7836.
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Formulation of polyurethanes is a complex problem poorly understood as it has developed more as an art rather than a science. Only a few experts have mastered polyurethane (PU) formulation after years of experience and the major raw material manufacturers largely hold such expertise. Understanding of PU formulation is at present insufficient to be developed from first principles. The first principle approach requires time and a detailed understanding of the underlying principles that govern the formulation process (e.g. PU chemistry, kinetics) and a number of measurements of process conditions. Even in the simplest formulations, there are more that 20 variables often interacting with each other in very intricate ways. In this doctoral thesis the use of the Case-Based Reasoning and Artificial Neural Network paradigm is proposed to enable support for PUs formulation tasks by providing a framework for the collection, structure, and representation of real formulating knowledge. The framework is also aimed at facilitating the sharing and deployment of solutions in a consistent and referable way, when appropriate, for future problem solving. Two basic problems in the development of a Case-Based Reasoning tool that uses past flexible PU foam formulation recipes or cases to solve new problems were studied. A PU case was divided into a problem description (i. e. PU measured mechanical properties) and a solution description (i. e. the ingredients and their quantities to produce a PU). The problems investigated are related to the retrieval of former PU cases that are similar to a new problem description, and the adaptation of the retrieved case to meet the problem constraints. For retrieval, an alternative similarity measure based on the moment's description of a case when it is represented as a two dimensional image was studied. The retrieval using geometric, central and Legendre moments was also studied and compared with a standard nearest neighbour algorithm using nine different distance functions (e.g. Euclidean, Canberra, City Block, among others). It was concluded that when cases were represented as 2D images and matching is performed by using moment functions in a similar fashion to the approaches studied in image analysis in pattern recognition, low order geometric and Legendre moments and central moments of any order retrieve the same case as the Euclidean distance does when used in a nearest neighbour algorithm. This means that the Euclidean distance acts a low moment function that represents gross level case features. Higher order (moment's order>3) geometric and Legendre moments while enabling finer details about an image to be represented had no standard distance function counterpart. For the adaptation of retrieved cases, a feed-forward back-propagation artificial neural network was proposed to reduce the adaptation knowledge acquisition effort that has prevented building complete CBR systems and to generate a mapping between change in mechanical properties and formulation ingredients. The proposed network was trained with the differences between problem descriptions (i.e. mechanical properties of a pair of foams) as input patterns and the differences between solution descriptions (i.e. formulation ingredients) as the output patterns. A complete data set was used based on 34 initial formulations and a 16950 epochs trained network with 1102 training exemplars, produced from the case differences, gave only 4% error. However, further work with a data set consisting of a training set and a small validation set failed to generalise returning a high percentage of errors. Further tests on different training/test splits of the data also failed to generalise. The conclusion reached is that the data as such has insufficient common structure to form any general conclusions. Other evidence to suggest that the data does not contain generalisable structure includes the large number of hidden nodes necessary to achieve convergence on the complete data set.
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Wang, Feng. "Polydimethylsiloxane Modification of Segmented Thermoplastic Polyurethanes and Polyureas." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30687.
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This thesis addresses the systematic modification of poly(tetramethylene oxide) (PTMO), polyether based segmented thermoplastic polyurethane with a secondary aminoalkyl functional polydimethylsiloxane (PDMS), which was intended to improve the fire resistance of polyurethane systems. The PDMS oligomer was successfully incorporated into the polyurethane backbone via one step solution polymerization. The effect of PDMS content on thermal stability, morphology, surface composition, mechanical properties, and fire resistance of polyurethane was investigated. These polymers displayed a complex two phase morphology and composition-dependant mechanical properties. The PDMS segment microphase separated from other polyurethane segments and varying microphase separation morphologies were observed with differing PDMS content. Spherical dispersed complex phases and co-continuous phases occurred when the PDMS content was 15wt% and 55wt%, respectively. Similar thermal stability was observed for both the polyurethane control and the PDMS modified polyurethanes, but the later displayed increased char yield in air with increased PDMS concentration. Quantitative measurements of the fire resistance of the modified polyurethanes by cone calorimetry showed that the peak heat release rate of the 15wt% siloxane modified samples dropped 67wt%, compared with the polyurethane control. However, the peak heat release rate did not further change with increasing siloxane content. Excellent mechanical properties, in terms of tensile strength and elongation, were found for the modified polyurethane with 15wt% of PDMS. Higher PDMS levels did reduce tensile strength, probably because of the reduction in strain crystallizing PTMO content. The PDMS modification, which resulted in improved fire resistance and excellent mechanical properties, is attributed to the low surface energy of the PDMS segment that tended to migrate to the surface of the polymer. It could be oxidized into a partially silicate-like material upon heating in air.
In addition, the syntheses of primary and secondary aminoalkyl functional PDMS based segmented polyureas are described herein. Two-phase morphology was observed for all the polyurea samples, even when the hard segment concentration was as low as 6wt%. All these polyureas formed clear transparent films that exhibited good mechanical properties even with very high PDMS content, up to 94wt%. They also demonstrated similar thermal stability, independent of the PDMS end group. However, the nature of the end group, i.e. primary or secondary aminoalkyl, had a dramatic effect on mechanical and morphological properties of these PDMS based polyureas, which was interpreted in terms of the level of hydrogen bonding.Ph. D.
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Kull, Kenneth. "Synthesis and Characterization of Novel Polyurethanes and Polyimides." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6530.
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Four novel high performance soft thermoplastic polyurethane elastomers utilizing methylene bis(4-cyclohexylisocyanate) as a hard segment, 1,4 butanediol as a chain extender and modified low crystallinity carbonate copolymer as a soft segment were synthesized. The samples were characterized by infrared spectroscopy (FTIR), tensile, elongation, hardness, abrasion resistance and atomic force microscopy (AFM). SAXS data shows evidence of an interdomain "center-to-center" distance of 45Å. DSC traces show evidence of one glass transition temperature and a weak melting region. DMA analysis reveals a low temperature secondary relaxation and the glass to rubber transition followed by a rubbery plateau. All samples demonstrated the ability to maintain excellent physical and mechanical properties in hardness below 70 Shore A. Thermoplastic polyurethanes in this study do not possess surface tackiness usually observed in soft polyurethanes. Biocompatability testing showed no toxicity of these samples as indicated by USP Class VI, MEM Elution Cytotoxicity and Hemolysis toxicology reports. This novel type of polyurethane material targets growing markets of biocompatible polymers and can be utilized as peristaltic pump tubing, balloon catheters, enteral feeding tubes and medical equipment gaskets and seals.
Polyimides are a family of engineering polymers with temperature stability, high polarity and solvent resistance. These high-performance materials are used in aerospace applications, in the production of semi-dry battery binders, and in a host of other high temperature demanding situations. However, their glass transition and melt temperatures are characteristically very high and close to one another, making them difficult to melt process and limiting them to thin film formulations from their polyamic acid precursors. Here, a new series of thermoplastic polyether-polyimides (PE-PIs) are synthesized by incorporating a polyetherdiamine monomer to reduce rigidity and break up an otherwise fully aromatic backbone as seen with most conventional polyimides. It will be shown that control of the stoichiometric ratio between the aromatic 4,4'-methylenebis(2,6-dimethylaniline) and aliphatic polyetherdiamines relative to PMDA (pyromellitic dianhydride), along with the molecular weight of the polyetheramine, can be used to tune the Tg to best balance between temperature performance and processability.
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Davis, Geoffrey P. "Transparent polyurethanes : synthesis, characterisation and mustard gas resistance." Thesis, Loughborough University, 1987. https://dspace.lboro.ac.uk/2134/11238.
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Transparent Polyurethanes based upon Polycaprolactone and H 12MDIisocyanate (Desmodur W) have been synthesised and tested with regard to permeation by Mustard Gas (HD). Variations in soft segment molecular weight, reaction ratio, and chain extender, as well as the effect of crosslinking have been investigated. It was found that the principal factor governing permeation behaviour was soft segment molecular weight. However as hard segment content increased the determinant role of the soft segment diminished. Morphological Analysis of the synthesised polyurethanes was carried out using DSC, CMI'A, GPC, and WAXD techniques. The physical properties (Hardness, Tensile Strength, etc) of these materials were also determined. Results showed that the use of mixed diol chain extenders or trifunctional crosslinking elements produced increased phase mixing in the polyurethanes as a consequence of poorer hard segment domain organisation. This had the effect of reducing soft segment restrictions such that poorer permeation performance was obtained. GPC and DSC Analysis of the various polycaprolactones used in the synthesis programme suggested that the lower molecular weight polyols (550-2000) were composed of at least two different molecular weight species. Work with mixed polyol formulations indicated this may affect the physical properties of the polyurethanes. GPC Analysis of the synthesised polyurethanes themselves showed a wide variety of molecular weights were obtained; these were seen to be very dependent upon polyol molecular weight. The CAPA 210 (1000 Mol.Wt.) based elastorners had the highest Mn values. It is believed these variations in molecular weight are related to the presence of different catalysts, activators, etc in the original polyols. Injection Moulding trials were carried out on the formulation considered to be the most promising candidate for the face mask material. Slight changes in physical properties were obtained as processing conditions were varied. Most significantly the polyurethane began to shown signs of yellowing at high injection temperatures (190°C and above).
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Avadhani, C. V. "Synthesis of diisocyanates, polyurethanes and thermally stable polymers." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 1991. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2991.
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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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Lind, Pernilla. "Biomarkers of aromatic isocyanates in exposed workers." Lund : Dept. of Occupational and Environmental Medicine, Institute of Laboratory Medicine, Lund University, 1997. http://catalog.hathitrust.org/api/volumes/oclc/39725787.html.
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Lau, Soo-Khim. "The structure-property relationships of urethane-acrylic thermosetting systems." Thesis, Loughborough University, 1995. https://dspace.lboro.ac.uk/2134/27415.
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Urethane-acrylic copolymers have found increasing use as a radiation curable materials in the recent years. These copolymers are highly crosslinked through the use of acrylic monomers having more than one double bond. Stirling Lloyd had discovered such materials to be a successful alternative to the urethane or acrylics coatings as waterproof membrane coatings. In this project, structure-property relationships of UA copolymer systems were studied. These were peroxide cured at room temperature.
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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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Lancaster, Ian M. "Synthesis, structure and properties of polyurethane-polymethacrylate graft polymers." Thesis, University of Bradford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236472.
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Lee, Yein-ming Leo. "Fundamental studies in reactive processing of polyurethane based polymerizations /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487322984316763.
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Yelisetty, Satya Suresh. "Modeling and experimentation of polyol + blowing agent systems a thesis presented to the faculty of the Graduate School, Tennessee Technological University /." Click to access online, 2008. http://proquest.umi.com/pqdweb?index=54&sid=1&srchmode=1&vinst=PROD&fmt=6&startpage=-1&clientid=28564&vname=PQD&RQT=309&did=1605147071&scaling=FULL&ts=1251389293&vtype=PQD&rqt=309&TS=1251389306&clientId=28564.
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Wang, Jinghong. "A study of smoldering combustion in horizontally oriented polyurethane foam layer /." View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?MECH%202002%20WANGJ.
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Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2002.Includes bibliographical references (leaves 154-166). Also available in electronic version. Access restricted to campus users.
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Piechová, Jana. "Biodegradace organických látek aplikací termofilní kultury." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2008. http://www.nusl.cz/ntk/nusl-216214.
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The aim of this work is focused on biodegradability study of modified polyurethane materials (foams and foils) in glukose medium and biodegradation of whey. The biodegradability was tested with using mixed thermophilic aerobic bacterial culture of the Bacillus and Thermus genera. The cultivations were practised in the fermentor and in Erlenmayer flasks in a heated shaker. Maximal reduction of COD and culture growth has been achieved by biodegradation of polyuretane in the fermentor. Main effect of degradation was abiotic destruction of PUR materials and consequent utilization of degradation products by bacterial culture. These tests indicated that the best modification agent for biodegradation was 10% carboxymethyl cellulose. The polyurethane foam was more decomposed then the polyurethane foil. Biodegradation of whey without proteins in the fermentor was detected decrease of CHSK and lactose concentration about 50 % in 20th hour. Optimal conditions for whey biodegradation with the thermophilic bacterial culture were pH 6,5 and temperature 60 °C.
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McMillan, Robin Scott. "Peptide-modified gold-coated polyurethanes as biosynthetic vascular prostheses." Thesis, University of Ottawa (Canada), 1998. http://hdl.handle.net/10393/4236.
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Healthy vasculature possesses a single layer of vascular endothelial cells on the interior lumen of the vessel. It is these cells that are responsible for the non-thrombogenicity of the natural blood vessel lumen. The generation of this layer on the surface of an artificial graft could provide the necessary non-thrombogenic properties to the artificial prosthesis. In this work, synthetic cell adhesion peptides were designed, synthesized and chemisorbed onto the surface of a gold coated polyurethane. The polymer substrate was chosen in order to maintain good mechanical properties in the artificial vein or artery, while the gold coating served the purpose of permitting surface modification with the cell adhesion peptides. The peptides were custom designed to specifically be active to cell surface receptors on vascular endothelial cells. The peptides also contained a thiol present in a cysteine amino acid which was necessary for interaction with the gold on the polymer surface. The modifications to the surface were confirmed by various methods including water contact angles, and surface analysis techniques such as: x-ray photoelectron spectroscopy, atomic force microscopy and scanning electron microscopy. The surfaces were tested for their ability to promote the initial attachment of both vascular endothelial cells and mouse 3T3 fibroblasts. (Abstract shortened by UMI.)
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McMillan, Robin. "Peptide modified gold coated polyurethanes as biosynthetic vascular prostheses." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0001/MQ36721.pdf.
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Kirschbaum, Stefan [Verfasser]. "Vinyl ether functional polyurethanes as novel photopolymers / Stefan Kirschbaum." Mainz : Universitätsbibliothek Mainz, 2017. http://d-nb.info/1125907592/34.
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Zemach, Kenneth David. "Segmented polyurethanes containing diacetylene units in multiple molecular environments." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/39050.
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Sun, Zhan. "X-ray analysis of structures of polyurethanes and copolyesters." Case Western Reserve University School of Graduate Studies / OhioLINK, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=case1059072340.
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Liu, Xiaohong. "Synthesis and Characterization of Carbohydrate-conjugated Polyesters and Polyurethanes." University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1491433530882435.
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