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Polyurethane
Kinds of Polyurethane Terms modified by Polyurethane Selected AbstractsSynthesis and studies of the physical properties of polyaniline and polyurethane-modified epoxy compositesPOLYMER ENGINEERING & SCIENCE, Issue 2 2008Wen-Chin Chiou Two series of toughened, semiconductive polyaniline (PANI)/polyurethane (PU)-epoxy (PANI/PU-EPOXY) nano-composites were prepared using a conductive polymer, PANI, and PU prepolymer-modified-diglycidyl ether of bisphenol A (DGEBA) epoxy. First, the PU prepolymer-modified epoxy oligomer was synthesized by a stoichiometric reaction between the terminal isocyanate groups of the PU prepolymer and the pendent hydroxyl groups of the epoxide. PU prepolymers were made either of polyester (polybutylene adipate, PBA) or polyether (polypropylene glycol, PPG) segments. The composites were characterized by thermal, morphological, mechanical, and electrical studies. Impact strength was enhanced 100% in PU (PPG 2000)-modified composites; whereas, only ca. 30,50% increases in impact strength were observed for the other modified composites. In addition, the thermal stability of this composite proved superior to that of neat epoxy resin, regardless of a PU content at 27.5 wt%. Scanning electron microscopy (SEM) morphology study showed that the spherical PU (PPG 2000) particles (ca. 0.2,0.5 ,m) dispersed within the matrix accounts for these extraordinary properties. The conductivity of the composite increased to ca. 10,9,10,3 S cm,1 upon addition of PANI when tested in the frequency range 1 kHz,13 MHz. This study demonstrated a useful way to simultaneously improve the toughness and conductivity of the epoxy composite, thus rendering it suitable for electromagnetic interference and various charge dissipation applications. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers [source] Self-Crimping Bicomponent Nanofibers Electrospun from Polyacrylonitrile and Elastomeric Polyurethane,ADVANCED MATERIALS, Issue 22 2005T. Lin Nanofibers with side-by-side morphologies are electrospun from polyacrylonitrile and polyurethane using a microfluidic device. Laminar flow of the two polymer solutions through the device results in nanometer-diameter curly nanofibers with bicomponent cross-sections. The polyurethane half of the nanofibers can be dissolved in tetrahydrofuran, leaving a "U"-shaped cross-section as seen in the Figure. [source] Polyurethane- and Polystyrene-Supported 2,2,6,6-Tetramethyl- piperidine-1-oxyl (TEMPO); Facile Preparation, Catalytic Oxidation and Application in a Membrane ReactorADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2008Muhammad Afzal Subhani Abstract In this contribution, the facile synthesis of two new polymer-supported 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) catalysts and their application in the catalytic oxidation of alcohols to carbonyl compounds are described. For attachment of the TEMPO group to the polymer an isocyanate functionalized polymer is chosen. This new approach facilitates the synthesis in comparison with previously existing methods which generally require deprotonation of TEMPO prior to reaction with the polymer. Following this approach, polyurethane (PU)- and polystyrene (PS)-based TEMPO catalysts are prepared in a one-step reaction from commercially available compounds. Both polymer-supported catalysts showed promising yields for a variety of substrates using inorganic and/or organic co-oxidants in biphasic and/or monophasic systems. The recyclability of the corresponding catalysts was studied in repetitive batch experiments using filtration or distillation depending on the support type. Furthermore, application of the homogeneous polyurethane-supported TEMPO for the selective oxidation of benzyl alcohol in a continously operated membrane reactor is demonstrated. [source] Polyurethane/acrylate hybrids: Effects of the acrylic content and thermal treatment on the polymer propertiesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Pablo J. Peruzzo Abstract Polyurethane (PU)/acrylate hybrids with different acrylic contents (10, 30, 50, 70, and 90 wt %) were prepared by the polymerization of acrylic monomers in the presence of preformed PU chains with polymerizable terminal vinyl groups. Films obtained by the casting of polymer dispersions before and after thermal annealing were characterized by dynamic light scattering, Fourier transform infrared spectroscopy, transmission electron microscopy (TEM), TEM electron energy-loss spectroscopy, differential scanning calorimetry, and gel fraction determination. Small-angle X-ray scattering (SAXS), wide-angle X-ray scattering, mechanical properties testing, atomic force microscopy, water contact angle testing, Buchholz hardness testing, and roughness testing of the films were also performed. The effects of the acrylic content and thermal treatment on the structure and properties were determined. TEM showed that a core,shell morphology was formed during polymerization. When the acrylic content increased, smaller particles without core,shell morphologies were observed. TEM energy-loss spectroscopy studies confirmed this observation. Systems with up to 50 wt % acrylic component were homogeneous, as determined by SAXS, before and after thermal annealing. An attempt to incorporate a higher amount of acrylic component led to phase-separated materials with a different morphology and, therefore, different properties. The relationship between the acrylic content and properties did not follow linear behavior. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Thermal stability and molecular interaction of polyurethane nanocomposites prepared by in situ polymerization with functionalized multiwalled carbon nanotubesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008R. N. Jana Abstract Polyurethane (PU) nanocomposites were prepared through conventional and in situ methods with multiwalled carbon nanotubes (MWNTs) functionalized with poly(,-caprolactone). The thermal degradation and stability of PU,MWNT nanocomposites were investigated with nonisothermal thermogravimetry and were explained in terms of the interaction between MWNTs and PU molecules with Fourier transform infrared spectroscopy. The difference in thermal stability between the conventional and in situ nanocomposites was also compared. The thermal degradation of all the nanocomposite samples took place in two stages and followed a first-order reaction. The degradation temperature of the in situ nanocomposites was higher than that of the conventional nanocomposites with the same loading of MWNTs. The activation energy at 10% degradation and the half-life period were also higher in the in situ nanocomposites compared to the conventional nanocomposites. Such higher thermal stability of the in situ nanocomposites was ascribed to covalent bond formation between MWNTs and PU chains, which could result in better dispersion of MWNTs in the PU matrix for the in situ nanocomposites than for the conventional nanocomposites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] FTIR, 1H-NMR spectra, and thermal characterization of water-based polyurethane/acrylic hybridsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008O. R. Pardini Abstract Polyurethane (PU) polymer was synthesized following a prepolymer mixing process, by polyaddition of isophorone diisocyanate (IPDI), poly(propylene glycol) (PPG), 2-hydroxyethyl methacrylate (HEMA), and 2,2-bis(hydroxymethyl)propionic acid (DMPA). The PU anionomer having 2-ethoxymethacrylate terminal groups was dispersed in water by prior neutralization of carboxylic acid groups of DMPA with triethylamine (TEA), chain extended with hydrazine (HZM) in water and a dispersion polymerization with methyl methacrylate/n -butyl acrylate/acrylic acid mixture was performed. The above polymerization reactions lead to the formation of PU/acrylic hybrids having a chemical bond between PU and acrylic moieties. Acrylic content was varied from 0 to 50 wt % and samples were purified to eliminate oligomers and impurities before characterization. The FTIR and 1H-NMR spectra of these purified hybrid samples were obtained and bands and peaks assignments were discussed. Thermal properties (DSC and TGA) were also discussed. Breaking hydrogen bonds is the main reason for changes in properties with increasing acrylic content. Particle size data of dispersions is also presented and discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Investigations of Miscibility in Interpenetrated Systems of Polyurethane and Polystyrene Obtained at Room TemperatureMACROMOLECULAR SYMPOSIA, Issue 1 2004Jean-Michel Widmaier Abstract Interpenetrating polymer systems based on crosslinked polyurethane (PU) and polystyrene (PS) were prepared at room temperature by a one-shot (in situ) method, starting from an initial homogeneous mixture of reagents via non interfering mechanisms. Both polymerizations were performed either simultaneously or one after the other. Crosslinks and/or covalent bonds between components were deliberately introduced by the addition of appropriate monomers, in order to tailor the degree of microphase separation. Depending on the formation process, transluscent or transparent films were obtained, despite the difference in refractive index of the components. The maximum of miscibility, taken as from the glass transition criterion, was obtained for sequential tightly graft interpenetrating networks. [source] Effects of solvent, film thickness, and hydrogen bonding on surface-relief gratingsPOLYMER ENGINEERING & SCIENCE, Issue 5 2009Woo-Hyuk Jung This work focuses on the development of a new type of surface-relief grating (SRG) using more effective materials than a typical epoxy-based azopolymer for the recording layer of optical data storage. Thus, aniline-based azopolymers were synthesized by reaction of N,N -diglycidylaniline with aniline (An) followed by diazocoupling with 4-aminobenzonitrile or 4-nitroaniline. Such azopolymers when spin-cast from THF/dioxane showed better diffraction efficiency than those cast from THF alone due to residual dioxane creating a large free volume in the solid state. A second diazocoupling reaction of the diazopolymers initially obtained produced polymers with bis(diazobenzene) substituents which exhibited a higher saturation level of the diffraction efficiency for a thicker than for a thinner film. Azopolymers in which the diazo substituents incorporated hydroxyl groups ortho to the diazo unit were obtained via the reaction of the diglycidyl ether of bisphenol-A with aniline or 3-hydroxyaniline followed by coupling with diazotised hydroxynitroaminobenzene. These hydroxy groups, presumably as a result of their H-bonding to the diazo-N, effectively prevented the photoisomerization of the chromophores, so that the polymers showed no SRG at a normal laser intensity of 100 mW/cm2. Polyurethane-based azopolymers, synthesized with toluene-2,4-diisocyanate and disperse orange 17 containing no hydroxyl groups in the main chains, showed better diffraction efficiency than the other azopolymers with nitro group substituents. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers [source] Polyurethane and sulfonated polysulfone blend ultrafiltration membranes: II.POLYMER INTERNATIONAL, Issue 3 2003Application studies Abstract Ultrafiltration membranes are largely being applied for macromolecular and heavy metal ion separations from aqueous streams. Polyurethane- and sulfonated- polysulfone-based membranes prepared in the absence and presence of the polymeric additive, poly(ethylene glycol) 600, in various compositions, were subjected to the rejection of macromolecular proteins, such as bovine serum albumin, egg albumin, pepsin and trypsin. Toxic heavy metal ions such as Cu2+, Ni2+, Cd2+ and Zn2+ were subjected to rejection by the blend membranes by complexing them with a polymeric ligand, polyethyleneimine. The effects of polymer blend compositions and additive concentrations on the rejection and permeate flux of both proteins and metal ions are discussed. The rejection and permeate flux efficiencies of the blend membranes are compared with pure sulfonated polysulfone membranes. © 2003 Society of Chemical Industry [source] Preparation and Fluorescent and Magnetic Properties of Polyurethane/Eu(MA)3 FilmsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 24 2007Shuxue Zhou Abstract Europium(III) (Eu3+)-doped polyurethane films were prepared by mixing Eu-methacrylic acid complex (Eu(MA)3) with aliphatic polyurethane oligomer and subsequently curing under UV irradiation. Transmission electron microscopy photos and the appearance of the resulting hybrid films showed that phase separation occurred only at an Eu(MA)3 content above 20 wt.-%. Fluorescence spectra indicated that the fluorescence of Eu3+ was barely influenced by the polyurethane matrix and its intensity increased with an Eu(MA)3 content in the range of approximately 0 to 10 wt.-%. An obvious applied external-field-dependent magnetization (M) of polyurethane/Eu(MA)3 films, namely, an increasing M at low field and a decreasing M at high field, was observed at room temperature from the hysteresis loops, which was influenced by both the Eu(MA)3 content and the ultrasonication imposed on the coatings before curing. It seems that ultrasonication leads to a thermodynamically-unstable structure of Eu3+ in hybrid films, which can be fixed by UV curing but gradually rearranges to its original form during the thermal-curing process, and enhances the diamagnetic part of the hybrid film. Thus, the magnetic property of Eu3+ -doped polyurethane film at room temperature can be adjusted by simply changing the preparation method and the Eu(MA)3 content instead of the type of Eu3+ -organic complex. [source] Polyurethane networks from different soy-based polyols by the ring opening of epoxidized soybean oil with methanol, glycol, and 1,2-propanediolJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2009Cheng-Shuang Wang Abstract A series of polyols with a range of hydroxyl (OH) numbers based on soybean oil and epoxidized soybean oil were prepared by oxirane ring opening with methanol, glycol, and 1,2-propanediol. The polyols, with average functionalities varying from 2.6 to 4.9, were characterized. Novel cast polyurethane resins were synthesized from these polyols and 2,4-toluene diisocyanate. The sol fraction of the network decreased as the OH number of the polyol from which it was synthesized increased. None of the samples were completely soluble. The crosslinking density of the polyurethanes correlated directly with the functionality of the polyols. The thermal and mechanical properties of the cast resins were characterized with differential scanning calorimetry and thermogravimetry. The glass-transition temperature increased with the OH number increasing, and the thermal stability of the resins was slightly decreased with the OH number increasing. The tensile strength at break increased with the OH number increasing. Polyurethanes prepared from polyols with OH numbers higher than 170 mg of KOH/g were glassy, whereas those with OH numbers below that value were rubbery. Glassy polyurethanes displayed decent mechanical strength, whereas rubbery samples showed relatively poor elastic properties and were characterized by lower strength. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Hydroxylated Linear Polyurethanes Derived from Sugar AlditolsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 6 2009Romina Marín Abstract A set of linear [m,n]-type polyurethanes was synthesized by reaction of HDI or MDI with conveniently protected sugar alditols L -threitol (LTh), L -arabinitol (LAr) and xylitol (Xy). of the resulting polyurethanes ranged between 10,000 and 60,000 with polydispersities around 2. They were thermally stable, showing no decomposition up to temperatures near 300,°C. They all were amorphous polymers with Tg highly dependent on the constitution of the diisocyanate, but scarcely dependent on the structure of the alditol. Hydrogenation of the LThBn-HDI polyurethane yielded partially debenzylated products with Tg values ranging between 20 and 30,°C. Fully benzylated polyurethanes showed high resistance to hydrolytic degradation, whereas polyurethane with free hydroxyl side groups degraded significantly in saline buffer at pH,=,10 and 37,°C. [source] Polyurethanes Based on Castor Oil: Kinetics, Chemical, Mechanical and Thermal PropertiesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 11 2008Elodie Hablot Abstract Polyurethanes based on vegetable oil were synthesized with castor oil and toluene diisocyanate, isophorone diisocyanate or hexamethylene diisocyanate, using dibutyltin dilaurate as a catalyst. The effects of the nature of the diisocyanate on the evolution of the kinetics, as well as the physical and mechanical properties and the thermal stability, of the different synthesized polyurethanes were investigated, and these complement data from the literature on equivalent systems. The polymerization kinetics, degree of swelling and mechanical properties were greatly affected by the diisocyanate nature, whereas the rheological properties and thermal stability were found to be similar for all polyurethanes. [source] Thermoplastic Polyurethanes with Poly(butylene terephthalate) as Crystallizable Hard PhaseMACROMOLECULAR MATERIALS & ENGINEERING, Issue 3 2008Debasish De Abstract Polyurethanes were prepared from poly(tetramethylene oxide) end-capped with MDI and PBT extenders. The PBT extenders were random-disperse in length and their length varied from three to seven repeating units. The structure of the polyurethanes was studied by FT-IR and AFM, their thermal and thermomechanical responses were measured by DSC and DMTA, and their elastic behavior was assessed by compression set measurements. The MDI-PBT-MDI hard segments had a ribbon-like crystalline morphology. Increasing the PBT length gave rise to an increase of the storage modulus at room temperature and the melting point. The storage modulus depended strongly on temperature. [source] Polyurethanes with Pendant Hydroxyl Groups: Synthesis and CharacterizationMACROMOLECULAR RAPID COMMUNICATIONS, Issue 3 2004Luc Ubaghs Abstract Communication: Phenoxycarbonyloxymethyl ethylene carbonate 4 was synthesized from glycerol carbonate and phenyl chloroformate. Polyurethanes with pendant hydroxyl groups were obtained from polycondensation reactions of this AA* monomer with diamines. These polymers contain primary as well as secondary hydroxyl groups. The obtained polyurethanes are amorphous materials. The glass transition temperature decreases with increasing number of methylene groups between the urethane groups. As the number of methylene groups increases between the urethane groups, the glass transition temperature of the polymer decreases. [source] Synthesis and characterization of novel thermoplastic poly(oligophosphazene-urethane)sPOLYMER INTERNATIONAL, Issue 6 2009Yubo Zhou Abstract BACKGROUND: Polyurethanes are some of the most popular polymers used in a variety of products, such as coatings, adhesives, flexible and rigid foams, elastomers, etc. Despite the possibility of tailoring their properties, polyurethanes suffer a serious disadvantage of poor thermal stability. Many attempts have been made in order to improve the thermal stability of polyurethanes. RESULTS: A new hydroxyl-terminated oligomer containing sulfone groups, 2,2-bis(4-hydroxy-4,4-sulfonyldiphoneloxy)tetraphenoxyoligocyclotriphosphazene (HSPPZ), was synthesized. HSPPZ was characterized using Fourier transform infrared (FTIR), NMR and gel permeation chromatography analyses. A series of novel thermoplastic poly(oligophosphazene-urethane)s were then synthesized via the reaction of NCO-terminated polyurethane prepolymer with HSPPZ containing chain-extender diols. Their structure and properties were investigated using FTIR spectroscopy, thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, water contact angle measurement and tensile measurements. CONCLUSION: Compared to conventional thermoplastic polyurethanes, poly(oligophosphazene-urethane)s exhibit better thermal stability, low-temperature resistance and hydrophobicity, but their mechanical properties are slightly poorer. Copyright © 2009 Society of Chemical Industry [source] Latex allergy: diagnosis and managementDERMATOLOGIC THERAPY, Issue 4 2004James S. Taylor ABSTRACT:, Latex allergy is an IgE-mediated immediate hypersensitivity response to natural rubber latex (NRL) protein with a variety of clinical signs ranging from contact urticaria, angioedema, asthma, and anaphylaxis. Major allergens include dipped latex products such as gloves and balloons. In highest risk for NRL allergy are patients with spina bifida, but health care workers and others who wear latex gloves are also at risk. NRL allergic patients may also react to fruits/foods, especially banana, kiwi, and avocado. Diagnosis is made by a positive latex RAST and/or skin prick test or challenge test to NRL. Allergen avoidance and substitution and the use of latex-safe devices including synthetic gloves (vinyl, synthetic polyisoprene, neoprene, nitrile, block polymers, or polyurethane) are essential for the affected patient. Accommodation in the workplace may include the use of powder-free, low-allergen NRL gloves or synthetic gloves. These preventive measures have significantly reduced the prevalence of reported reactions to NRL. Hyposensitization is not yet feasible. [source] Double Modification of Electrode Surface for the Selective Detection of Epinephrine and Its Application to Flow Injection Amperometric AnalysisELECTROANALYSIS, Issue 22 2009Guang-Ri Xu Abstract A glassy carbon electrode having two polymer layers has been applied to selectively detect epinephrine. The inner layer formed by electropolymerization of macrocyclic nickel complex functioned as an electrocatalyst for epinephrine oxidation and the outer layer composed of hydrolyzed polyurethane ,-benzyl L -glutamate as a screening layer. Differential pulse voltammetry showed almost 100% recovery of epinephrine even in 100-fold excess of interferents. When applied to a dual glassy carbon electrode as an amperometric detector in flow injection analysis, a linear response over 0.1,,M and 10,,M was obtained. Recovery tested for 5-fold diluted human urine samples was 97.5%. [source] Stability Enhancement of All-Solid-State H+ ISEs with Cross-Linked Silicon-Urethane MatricesELECTROANALYSIS, Issue 8 2005Nak-Hyun Kwon Abstract An all-solid-state hydrogen-ion-selective electrode (ASHISE) was fabricated using the polymer hybrid membrane. Polymer membranes composed of Tecoflex polyurethane (TPU), polyvinyl chloride (PVC), silicon rubber (SR), and additives (KTpClPB, DOA, and TDDA) were cast on a carbon rod. The TPU/SR hybrid membrane exhibited a longer lifetime and a higher sensitivity in the sensing of the H+ ion compared to conventional TPU/PVC and PVC/SR hybrid membranes. Moreover, the addition of SiCl4 to TPU-based matrices enhanced the potentiometric response and ISE stability, due to the chemical bonding between Si and CO in urethane, in which the cross-linking configuration was confirmed by DSC, FT-IR, and XPS experiments. TPU/SR membranes containing SiCl4 were rendered more stable and showed a pH response over a wide range (i.e., pH,2,11.5) with the slope of 60±2,mV/pH for more than four months. The ASHISE exhibited a small interfering potential variation in the wide range of the salt concentration (from 1.0×10,6,M up to 0.1,M). The ASHISE showed a result comparable to a commercial clinical blood analyzer. [source] A Versatile Solvent-Free "One-Pot" Route to Polymer Nanocomposites and the in situ Formation of Calcium Phosphate/Layered Silicate Hybrid NanoparticlesADVANCED FUNCTIONAL MATERIALS, Issue 11 2010Hans Weickmann Abstract Poly(methyl methacrylate) (PMMA), polystyrene (PS), and polyurethane (PU) nanocomposites containing well-dispersed calcium phosphate/layered silicate hybrid nanoparticles were prepared in a versatile solvent-free "one-pot" process without requiring separate steps, such as organophilic modification, purification, drying, dispersing, and compounding, typical for many conventional organoclay nanocomposites. In this "one-pot" process, alkyl ammonium phosphates were added as swelling agents to a suspension of calcium/layered silicate in styrene, methyl methacrylate, or polyols prior to polymerization. Alkyl ammonium phosphates were prepared in situ by reacting phosphoric acid with an equivalent amount of alkyl amines such as stearyl amine (SA) or the corresponding ester- and methacrylate-functionalized tertiary alkyl amines, obtained via Michael Addition of SA with methyl acrylate or ethylene 2-methacryloxyethyl acrylate. Upon contact with the calcium bentonite suspension, the cation exchange of Ca2+ in the silicate interlayers for alkyl ammonium cations rendered the bentonite organophilic and enabled effective swelling in the monomer accompanied by intercalation and in situ precipitation of calcium phosphates. According to energy dispersive X-ray analysis, the calcium phosphate precipitated exclusively onto the surfaces of the bentonite nanoplatelets, thus forming easy-to-disperse calcium phosphate/layered silicate hybrid nanoparticles. Incorporation of 5,15,wt% of such hybrid nanoparticles into PMMA, PS, and PU afforded improved stiffness/toughness balances of the polymer nanocomposites. Functionalized alkyl ammonium phosphate addition enabled polymer attachment to the nanoparticle surfaces. Transmission electron microscopy (TEM) analyses of PU and PU-foam nanocomposites, prepared by dispersing hybrid nanoparticles in the polyols prior to isocyanate cure, revealed the formation of fully exfoliated hybrid nanoparticles. [source] Detailed determination of smoke gas contents using a small-scale controlled equivalence ratio tube furnace methodFIRE AND MATERIALS, Issue 8 2007Per Blomqvist Abstract A series of tests including seven different materials and products have been conducted using a controlled equivalence ratio tube furnace test method. The main objective of the tests was to determine yields of fire-generated products at defined combustion conditions. The tube furnace test method was set up and run in close agreement with that described in BS 7990:2003. At the time of experimental work the new tube furnace method was in the process of becoming an international standard. It was thus of interest to make an assessment of the capability of the method for determining production yields of important toxic fire products from different types of materials and products. The test series included solid wood, flexible polyurethane (PUR), fire-retarded rigid PUR, a polyvinyl chloride (PVC) carpet, a high-performance data cable with fluorine-containing polymer matrix, a PVC-based cable sheathing material and fire-retarded polyethylene cable insulation material. Duplicate tests were generally conducted at both well-ventilated and vitiated combustion conditions with these materials. The smoke gases produced from the combustion were quantified for inorganic gases by FTIR technique in all tests. A more detailed analysis of the smoke gases was conducted for some of the materials. This extended analysis contained a detailed assessment of organic compounds including, e.g. volatile organic compounds, isocyanates, aldehydes and polycyclic aromatic hydrocarbons. The analysis further included measurement of the size distribution of fire-generated particles for some of the materials. The quantification of toxic inorganic gases produced by combustion at both well-ventilated and vitiated conditions was successful regarding repeatability and stability. Typical yields for the two fire stages investigated were determined for a wide range of materials and products. The detailed analysis of organic compounds further corroborated that the new tube furnace method can replicate defined combustion conditions. Copyright © 2007 John Wiley & Sons, Ltd. [source] Polyurethane/clay and polyurethane/POSS nanocomposites as flame retarded coating for polyester and cotton fabricsFIRE AND MATERIALS, Issue 4-5 2002Eric Devaux Polyurethane resins (PU) are widely used as coatings for textile fabrics in order to improve some properties (for example mechanical behaviour, water repellency and air impermeability). Two kinds of additives have been added to the polyurethane in order to provide flame retardancy to the coated textile structure: montmorillonite clay and polyhedral oligomeric silsesquioxanes (POSS) have been used to process PU nanocomposites. The paper presents some results obtained with PU/clay and PU/POSS coated polyester or cotton fabrics, using cone calorimetry and thermogravimetric analysis. The efficiency of the additive chosen is clearly demonstrated and discussed. In particular, the great potential of using POSS for fire retardant applications is highlighted. Copyright © 2002 John Wiley & Sons, Ltd. [source] Self-Crimping Bicomponent Nanofibers Electrospun from Polyacrylonitrile and Elastomeric Polyurethane,ADVANCED MATERIALS, Issue 22 2005T. Lin Nanofibers with side-by-side morphologies are electrospun from polyacrylonitrile and polyurethane using a microfluidic device. Laminar flow of the two polymer solutions through the device results in nanometer-diameter curly nanofibers with bicomponent cross-sections. The polyurethane half of the nanofibers can be dissolved in tetrahydrofuran, leaving a "U"-shaped cross-section as seen in the Figure. [source] Stuck long-term indwelling central venous catheters in adolescents: three cases and a short topical reviewACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 6 2010A. MORTENSEN We present three cases of fixated vascular injection ports. Two patients had cystic fibrosis and one had an immunological defect. All catheters were made from polyurethane and implanted in adolescent patients. Indwelling time were 6,8 years. One patient's catheter was entirely integrated in the vessel wall and impossible to remove. In the other two cases, catheters were removed with great difficulty by the interventional radiologists. These cases raise important questions concerning the maximum indwelling time and the choice of catheter material when implanting permanent central venous catheters (CVCs) in adolescents. Furthermore, it highlights the importance of not breaking a CVC in the attempt to remove it. [source] Polyurethane- and Polystyrene-Supported 2,2,6,6-Tetramethyl- piperidine-1-oxyl (TEMPO); Facile Preparation, Catalytic Oxidation and Application in a Membrane ReactorADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2008Muhammad Afzal Subhani Abstract In this contribution, the facile synthesis of two new polymer-supported 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) catalysts and their application in the catalytic oxidation of alcohols to carbonyl compounds are described. For attachment of the TEMPO group to the polymer an isocyanate functionalized polymer is chosen. This new approach facilitates the synthesis in comparison with previously existing methods which generally require deprotonation of TEMPO prior to reaction with the polymer. Following this approach, polyurethane (PU)- and polystyrene (PS)-based TEMPO catalysts are prepared in a one-step reaction from commercially available compounds. Both polymer-supported catalysts showed promising yields for a variety of substrates using inorganic and/or organic co-oxidants in biphasic and/or monophasic systems. The recyclability of the corresponding catalysts was studied in repetitive batch experiments using filtration or distillation depending on the support type. Furthermore, application of the homogeneous polyurethane-supported TEMPO for the selective oxidation of benzyl alcohol in a continously operated membrane reactor is demonstrated. [source] Repigmentation of pretibial vitiligo with calcineurin inhibitors under occlusionJOURNAL DER DEUTSCHEN DERMATOLOGISCHEN GESELLSCHAFT, Issue 5 2008Anke Hartmann Summary Treatment of vitiligo is a challenge, especially in children. Recently, topical calcineurin inhibitors have been introduced in the management of vitiligo, but significant repigmentation is not achieved except on the face. Large pretibial lesions of a 15-year-old female with progressive vitiligo were treated twice daily over six months with 0.1% tacrolimus ointment on the right and 1% pimecrolimus cream on the left side without effect. Additional overnight occlusion with polyurethane and hydrocolloid foils during the following 18 months led to substantial repigmentation on both sides (tacrolimus-treated side, 88% repigmented area; pimecrolimus-treated side, 73%). Tacrolimus serum levels measured at four different time points did not exceed 1.8 ng/ml. This case report on a direct comparison of topical tacrolimus and pimecrolimus in vitiligo shows that on the shins considerable improvement could be induced with both agents only by additional long-term occlusion and that tacrolimus was somewhat more effective than pimecrolimus. [source] Structure and properties of cross-linked polyurethane copolymersADVANCES IN POLYMER TECHNOLOGY, Issue 3 2009S. Oprea Abstract Polyurethane elastomers based on polyester diols and aromatic or aliphatic diisocyanates can be used as vibration dampers and isolation materials. Two series of cross-linked polyurethanes with various hard segment structures and different amounts were prepared and thermomechanical properties of these materials were studied. Cross-linked polyurethane copolymers composed of poly(ethylene adipate)diol as soft segment and 4,4,-methylenebis(phenylisocyanate), 1,6-hexamethylene diisocyanate, and diols glycerin, 1,4-butanediol, and 1,6-hexanediol as hard segments were synthesized by a two-step process. The networks have been prepared by end-linking a mixture of the bifunctional precursor chains with trifunctional cross-linkers at off-stoichiometric ratios. The results show that the cross-link and the polyurethane hard segment interaction play a special role in the interconnected chain density and its magnitude is revealed by the mechanical properties. Of most importance, maximum stress, tensile modulus, and elongation at break increased significantly at the 22 wt % composition of hard segment content. Interchain cross-linking improves thermal stability, which was measured by thermogravimetric analysis and differential scanning calorimetry. Cross-linked polyurethane behaves as an elastomer and is useful for shock, noise, and vibration control. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:165,172, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20155 [source] Development of sustainable resource-based nanostructured polyaniline/castor oil polyurethane compositesADVANCES IN POLYMER TECHNOLOGY, Issue 1 2009Sharif Ahmad Abstract Processibility is one of the important requirements for the commercial utilization of conducting polymers. Studies on composites and blends based on nano polyaniline (PANI) dispersions have become the subject of scientific curiosity with regard to their morphology, stability, and electron transport properties. In general, polymer nanocomposites are made by dispersing inorganic or organic nanoparticles into either a conventional thermoplastic or thermoset polymer. The present study reports the synthesis of nanostructured MO-PANI and castor oil polyurethane (COPU),based composites. The effect of loading of nanostructured MO-PANI in COPU on the spectral, physicochemical and morphological properties has been analyzed. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:26,31, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20143 [source] The application of distance distribution functions to structural analysis of core,shell particlesJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2007Oleksandr O. Mykhaylyk The structure of core,shell latex particles of polymethylmethacrylate (the core) and polyurethane (the shell) have been investigated by methods of small-angle X-ray scattering (SAXS) and atom-force microscopy. A set of SAXS patterns has been obtained using contrast variation method. Indirect methods have been used to follow the evolution of distance distribution functions from SAXS for lattices in various sucrose solutions over a range of solution density, yielding structural parameters of the particles such as core size, shell thickness and density of the polymers including density deviations within the particle's core and shell. A model for an ensemble of core,shell particles with a normal distribution of average electron density of both the core and the shell has been developed to fit the distance distribution functions using a random search algorithm. The effects of nanophase separation in the polyurethane is estimated using Monte Carlo simulations of the distance distribution functions where the phase-separated polyurethane is represented by spherical truncated cones in a shell simulating the location of hard and soft polyurethane blocks, respectively. [source] Fungi are the predominant micro-organisms responsible for degradation of soil-buried polyester polyurethane over a range of soil water holding capacitiesJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2003S.R. Barratt Abstract Aims: To investigate the relationship between soil water holding capacity (WHC) and biodegradation of polyester polyurethane (PU) and to quantify and identify the predominant degrading micro-organisms in the biofilms on plastic buried in soil. Methods and Results: High numbers of both fungi and bacteria were recovered from biofilms on soil-buried dumb-bell-shaped pieces of polyester PU after 44 days at 15,100% WHC. The tensile strength of the polyester PU was reduced by up to 60% over 20,80% soil WHC, but no reduction occurred at 15, 90 or 100% soil WHC. A PU agar clearance assay indicated that fungi, but not bacteria were, the major degrading organisms in the biofilms on polyester PU and 10,30% of all the isolated fungi were able to degrade polyester PU in this assay. A 5·8S rDNA sequencing identified 13 strains of fungi representing the three major colony morphology types responsible for PU degradation. Sequence homology matches identified these strains as Nectria gliocladioides (five strains), Penicillium ochrochloron (one strain) and Geomyces pannorum (seven strains). Geomyces pannorum was the predominant organism in the biofilms comprising 22,100% of the viable polyester PU degrading fungi. Conclusions: Polyester PU degradation was optimum under a wide range of soil WHC and the predominant degrading organisms were fungi. Significance and Impact of the Study: By identifying the predominant degrading fungi in soil and studying the optimum WHC conditions for degradation of PU it allows us to better understand how plastics are broken down in the environment such as in landfill sites. [source] | ||||||||||||||||||||||||||||||||||