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Sample records for 88-3 urethane adhesive

  1. Compatibility of Halthane 88-3 urethane adhesive with the replacement cleaning solvent D-Limonene

    SciTech Connect

    LeMay, J.D.; Mendoza, B.

    1991-08-01

    D-Limonene, (R)1-methyl-4-isopropenyl-1-cyclohexene, has been identified as a leading replacement for chlorinated solvents traditionally used to clean electrical assemblies and critical components in some phases of weapons production. Unfortunately, d-limonene has a much lower vapor pressure than the chlorinated solvents if replaces (<2 torr at ambient). This makes its complete elimination from cleaned subassemblies potentially difficult, and gives rise to concerns about the compatibility of d-limonene with materials in the warhead. During the past year many WR polymers and adhesives have been surveyed for their compatibility with d-limonene. Preliminary test results obtained at Sandia (Albuquerque) and Allied-Signal (KCD) showed that Aluminum/Halthane 88-3/Aluminum joints were destroyed during exposure to saturated d-limonene vapor. The cause of bond failure appeared to be d-limonene induced swelling of the Halthane polymer. This report describes recent work performed at LLNL to study the swelling behavior and bond strength degradation of Halthane 88-3 resulting from exposure to d-limonene vapor.

  2. Urethane/Silicone Adhesives for Bonding Flexing Metal Parts

    NASA Technical Reports Server (NTRS)

    Edwards, Paul D.

    2004-01-01

    Adhesives that are blends of commercially available urethane and silicone adhesives have been found to be useful for bonding metal parts that flex somewhat during use. These urethane/silicone adhesives are formulated for the specific metal parts to be bonded. The bonds formed by these adhesives have peel and shear strengths greater than those of bonds formed by double-sided tapes and by other adhesives, including epoxies and neat silicones. In addition, unlike the bonds formed by epoxies, the bonds formed by these adhesives retain flexibility. In the initial application for which the urethane/silicone adhesives were devised, there was a need to bond spring rings, which provide longitudinal rigidity for inflatable satellite booms, with the blades that provide the booms axial strength. The problem was to make the bonds withstand the stresses, associated with differences in curvature between the bonded parts, that arose when the booms were deflated and the springs were compressed. In experiments using single adhesives (that is, not the urethane/ silicone blends), the bonds were broken and, in each experiment, it was found that the adhesive bonded well with either the ring or with the blade, but not both. After numerous experiments, the adhesive that bonded best with the rings and the adhesive that bonded best with the blades were identified. These adhesives were then blended and, as expected, the blend bonded well with both the rings and the blades. The two adhesives are Kalex (or equivalent) high-shear-strength urethane and Dow Corning 732 (or equivalent) silicone. The nominal mixture ratio is 5 volume parts of the urethane per 1 volume part of the silicone. Increasing the proportion of silicone makes the bond weaker but more flexible, and decreasing the proportion of silicone makes the bond stronger but more brittle. The urethane/silicone blend must be prepared and used quickly because of the limited working time of the urethane: The precursor of the urethane

  3. Solvent for urethane adhesives and coatings and method of use

    DOEpatents

    Simandl, Ronald F.; Brown, John D.; Holt, Jerrid S.

    2010-08-03

    A solvent for urethane adhesives and coatings, the solvent having a carbaldehyde and a cyclic amide as constituents. In some embodiments the solvent consists only of miscible constituents. In some embodiments the carbaldehyde is benzaldehyde and in some embodiments the cyclic amide is N-methylpyrrolidone (M-pyrole). An extender may be added to the solvent. In some embodiments the extender is miscible with the other ingredients, and in some embodiments the extender is non-aqueous. For example, the extender may include isopropanol, ethanol, tetrahydro furfuryl alcohol, benzyl alcohol, Gamma-butyrolactone or a caprolactone. In some embodiments a carbaldehyde and a cyclic amide are heated and used to separate a urethane bonded to a component.

  4. Improving adhesion between a segmented poly(ether-urethane) and a fluorocarbon copolymer coating

    SciTech Connect

    Hoffman, D.M.; Walkup, C.M.; Chiu, I.L.

    1984-01-01

    A moisture barrier coating of Kel-F 800, developed at LLNL to reduce uranium corrosion, had to be bonded to a porous ceramic. The adhesive could not bond too strongly or react with the coating and jeopardize its barrier properties. Methods of improving adhesion to the Kel-F coating were studied. Silane and titanate coupling agents and a fluorocarbon surfactant were somewhat effective at increasing adhesion depending on the application procedure. X-ray photoelectron spectroscopy (XPS) was used to demonstrate the presence of fluorosurfactant at the fracture interface. Postcuring at elevated temperatures (85/sup 0/C) also significantly improved adhesive strength to the fluorocarbon coating. This was attributed to thermal acceleration to interfacial diffusion of the urethane adhesive into the fluoropolymer surface.

  5. Enzyme-catalyzed hydrolysis of dentin adhesives containing a new urethane-based trimethacrylate monomer

    PubMed Central

    Park, Jong-Gu; Ye, Qiang; Topp, Elizabeth M.; Spencer, Paulette

    2009-01-01

    A new trimethacrylate monomer with urethane-linked groups, 1,1,1-tri-[4-(methacryloxyethylamino-carbonyloxy)-phenyl]ethane (MPE), was synthesized, characterized, and used as a co-monomer in dentin adhesives. Dentin adhesives containing 2-hydroxyethyl methacrylate (HEMA, 45% w/w) and 2,2-bis[4(2-hydroxy-3-methacryloyloxy-propyloxy)-phenyl] propane (BisGMA, 30% w/w) in addition to MPE (25% w/w) were formulated with H2O at 0 (MPE0), 8 (MPE8) and 16 wt % water (MPE16) to simulate the wet demineralized dentin matrix and compared with controls [HEMA/BisGMA, 45/55 w/w, at 0 (C0), 8 (C8) and 16 wt% water (C16)]. The new adhesive showed a degree of double bond conversion and mechanical properties comparable with control, with good penetration into the dentin surface and a uniform adhesive/dentin interface. On exposure to porcine liver esterase, the net cumulative methacrylic acid (MAA) release from the new adhesives was dramatically (P < 0.05) decreased relative to the control, suggesting that the new monomer improves esterase resistance. PMID:19582843

  6. A new fluorinated urethane dimethacrylate with carboxylic groups for use in dental adhesive compositions.

    PubMed

    Buruiana, Tinca; Melinte, Violeta; Aldea, Horia; Pelin, Irina M; Buruiana, Emil C

    2016-05-01

    A urethane macromer containing hexafluoroisopropylidene, poly(ethylene oxide) and carboxylic moieties (UF-DMA) was synthesized and used in proportions varying between 15 and 35 wt.% (F1-F3) in dental adhesive formulations besides BisGMA, triethylene glycol dimethacrylate and 2-hydroxyethyl methacrylate. The FTIR and (1)H ((13)C) NMR spectra confirmed the chemical structure of the UF-DMA. The experimental adhesives were characterized with regard to the degree of conversion, water sorption/solubility, contact angle, diffusion coefficient, Vickers hardness, and morphology of the crosslinked networks and compared with the specimens containing 10 wt.% hydroxyapatite (HAP) or calcium phosphate (CaP). The conversion degree (after 180 s of irradiation with visible light) ranged from 59.5% (F1) to 74.8% (F3), whereas the water sorption was between 23.15 μg mm(-3) (F1) and 40.52 μg mm(-3) (F3). Upon the addition of HAP or CaP this parameter attained values of 37.82-49.14 μg mm(-3) (F1-F3-HAP) and 34.58-45.56 μg mm(-3), respectively. Also, the formation of resin tags through the infiltration of a dental composition (F3) was visualized by SEM analysis. The results suggest that UF-DMA taken as co-monomer in dental adhesives of acrylic type may provide improved properties in the moist environment of the mouth. PMID:26952402

  7. Micro-structuring of polycarbonate-urethane surfaces in order to reduce platelet activation and adhesion.

    PubMed

    Clauser, Johanna; Gester, Kathrin; Roggenkamp, Jan; Mager, Ilona; Maas, Judith; Jansen, Sebastian V; Steinseifer, Ulrich

    2014-01-01

    In the development of new hemocompatible biomaterials, surface modification appears to be a suitable method in order to reduce the thrombogenetic potential of such materials. In this study, polycarbonate-urethane (PCU) tubes with different surface microstructures to be used for aortic heart valve models were investigated with regard to the thrombogenicity. The surface structures were produced by using a centrifugal casting process for manufacturing PCU tubes with defined casting mold surfaces which are conferred to the PCU surface during the process. Tubes with different structures defined by altering groove widths were cut into films and investigated under dynamic flow conditions in contact with porcine blood. The analysis was carried out by laser scanning microscopy which allowed for counting various morphological types of platelets with regard to the grade of activation. The comparison between plain and shaped PCU samples showed that the surface topography led to a decline of the activation of the coagulation cascade and thus to the reduction of the fibrin synthesis. Comparing different types of structures revealed that smooth structures with a small groove width (d ~ 3 μm) showed less platelet activation as well as less adhesion in contrast to a distinct wave structure (d ~ 90 μm). These results prove surface modification of polymer biomaterials to be a suitable method for reducing thrombogenicity and hence give reason for further alterations and improvements. PMID:24484511

  8. Using scratch testing to measure the adhesion strength of calcium phosphate coatings applied to poly(carbonate urethane) substrates.

    PubMed

    Barnes, Dunstan; Johnson, Scott; Snell, Robert; Best, Serena

    2012-02-01

    Bioactive coatings are applied to components of modern orthopædic implants to improve the host tissue response to the implants. Such coatings cannot be applied to polymeric implants by high-temperature techniques, because the use of high temperatures may critically degrade the polymer substrate. Regardless of the coating technique that is used, the coating must be sufficiently well adhered to the underlying substrate to provide any practical benefit. This paper investigates the use of scratch testing to measure the adhesion strength of calcium phosphate (CaP) coatings that were applied to a poly(carbonate urethane) (PCU) substrate by an aqueous process at temperatures of 19, 28, 37, and 50 °C. This work represents the first time that scratch testing analysis has been used to study CaP coatings deposited by an aqueous, low-temperature process on to a polymer substrate. Scratch testing was shown to be a useful technique for obtaining comparative, rather than absolute, values of adhesion strength for hard coatings formed on a compliant substrate. Generally, the coating temperature was not found to influence the CaP-PCU adhesion strength. Although CaP coatings formed at 19 °C exhibited considerably lower adhesion strengths than CaP coatings formed at 28, 37, and 50 °C, this finding was attributable to the inconsistency of CaP coatings formed on the PCU substrates at 19 °C. The coating-substrate adhesion strength was measured for CaP coatings of four different coating ages (0, 1, 2, and 3 years). CaP coatings that were aged for 0, 1, or 2 years exhibited similar coating-substrate adhesion strengths to each other. In contrast, CaP coatings that were aged for 3 years demonstrated considerably lower coating-substrate adhesion strengths. The observed reduction in adhesion strength with age was thought to be attributable to suspected "drying out" of the CaP coatings. PMID:22301182

  9. Exploratory study on the effects of novel diamine curing agents and isocyanate precursors on the properties of new epoxy and urethane adhesives

    NASA Technical Reports Server (NTRS)

    Glasgow, D. G.

    1976-01-01

    The effects of novel aromatic diamine structures on the adhesive properties of epoxy and polyurethane adhesives were studied. Aromatic diamines based on benzophenone and diphenyl-methane isomers were evaluated as curing agents for epoxy resins and benzophenone and diphenyl-methane based diamine isomers were evaluated as curing agents for polyurethane adhesives. Polyurethane adhesives were prepared based on m, m prime-diisocyanato-diphenyl-methane and m, m prime-diisocyanato-benzophenone. The m, m prime-diisocayanato-diphenyl-methane based adhesive had properties comparable to state-of-the-art adhesives. The m, m prime-diisocyanato-benzophenone based adhesive was extremely reactive.

  10. Exploratory study on the effects of novel diamine curing agents and isocyanate precursors on the properties on new epoxy and urethane adhesives

    NASA Technical Reports Server (NTRS)

    Glasgow, D. G.; Garthwait, C.

    1977-01-01

    Aromatic diamines based on diphenyl sulfone and benzophenone were studied as epoxy adhesive curing agents. Previously found differences in adhesive strengths for meta vs para orientation were not found in these series. The use of aluminum and alumina as fillers in a m,m prime-methylene dianiline-cured epoxy adhesive was not found to be beneficial to adhesive strength. Alumina filled adhesives had much lower strength than unfilled adhesives. The unfilled m,m prime-methylene dianiline-based epoxy adhesive had excellent resistance to moisture relative to a p,p prime-methylene dianiline-based adhesive and maintained good strengths up to 250 F. A glass fiber composite based on a m,m prime-methylene dianiline-cured epoxy appeared to be equivalent to the p,p prime-methylene dianiline-cured epoxy as judged by short beam shear tests.

  11. Exploratory Study on the Effects of Novel Diamine Curing Agents and Isocyanate Precursors on the Properties of New Epoxy and Urethane Adhesives

    NASA Technical Reports Server (NTRS)

    Glasgow, D. Gerald; Garthwait, Clayborn

    1977-01-01

    This report covers the results of investigations directed toward studying the effects of novel aromatic diamine structures on epoxy adhesive properties and includes work done under a modification to the original contract. Three aromatic diamines based on diphenylsulfone and benzophenone were studied as epoxy adhesive curing agents. Previously found differences in adhesive strengths for meta vs para orientation were not found in these series. The use of aluminum and alumina as fillers in a m,m'-methylene dianiline-cured epoxy adhesive was not found to be beneficial to adhesive strength. Alumina filled adhesives had much lower strength than unfilled adhesives. The unfilled m,m'-methylene dianiline-based epoxy adhesive had excellent resistance to moisture relative to a p,p'-methylene dianiline-based adhesive and maintained good strengths up to 250 F. A glass fiber composite based on a m,m'-methylene dianiline-cured epoxy appeared to be equivalent to the p,p'-methylene dianiline-cured epoxy as judged by short beam shear tests.

  12. 9 CFR 88.3 - Standards for conveyances.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 9 Animals and Animal Products 1 2010-01-01 2010-01-01 false Standards for conveyances. 88.3 Section 88.3 Animals and Animal Products ANIMAL AND PLANT HEALTH INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE INTERSTATE TRANSPORTATION OF ANIMALS (INCLUDING POULTRY) AND ANIMAL PRODUCTS...

  13. 9 CFR 88.3 - Standards for conveyances.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 9 Animals and Animal Products 1 2011-01-01 2011-01-01 false Standards for conveyances. 88.3 Section 88.3 Animals and Animal Products ANIMAL AND PLANT HEALTH INSPECTION SERVICE, DEPARTMENT OF AGRICULTURE INTERSTATE TRANSPORTATION OF ANIMALS (INCLUDING POULTRY) AND ANIMAL PRODUCTS...

  14. Adhesion

    MedlinePlus

    ... adhesions Ovarian cyst References Munireddy S, Kavalukas SL, Barbul A. Intra-abdominal healing: gastrointestinal tract and adhesions. Surg Clin N Am Kulaylat MN, Dayton, MT. Surgical complications. In: Townsend CM Jr, Beauchamp RD, Evers BM, Mattox KL, ...

  15. Alkane-Based Urethane Potting Compounds

    NASA Technical Reports Server (NTRS)

    Morris, D. E.

    1986-01-01

    New low viscosity urethanes easily mixed, molded, and outgassed. Alkane-based urethanes resist hydrolysis and oxidation and have excellent dielectric properties. Low-viscosity alkane-based urethane prepolymer prepared by one-step reaction of either isophorone diisocyanate or methyl-bis (4-cyclohexyl isocyanate) with hydrogenated, hydroxy-terminated polybutadiene (HTPBD).

  16. Mesoporous hybrid organosilica containing urethane moieties

    SciTech Connect

    Seo, You-Kyong; Park, Sung-Bae; Ho Park, Dong . E-mail: chempdh@inje.ac.kr

    2006-04-15

    Mesoporous hybrid material containing urethane moieties in functionalized long chain organic group have been synthesized by using bis[3-(triethoxysilyl) propyl urethane]ethane (BTESPUE) and tetraethoxysilane as structural ingredients. The incorporation of BTESPUE within the framework of mesoporous material was confirmed by Fourier transform-infrared, X-ray photoelectron spectroscopy, solid-state NMR spectroscopy and thermogravimetric analysis. This material had a thick wall and uniform pore, which may be attributed to the hydrogen bonding inside framework due to urethane moieties.

  17. Poly(hydroxyl urethane) compositions and methods of making and using the same

    DOEpatents

    Luebke, David; Nulwala, Hunaid; Tang, Chau

    2016-01-26

    Methods and compositions relating to poly(hydroxyl urethane) compounds are described herein that are useful as, among other things, binders and adhesives. The cross-linked composition is achieved through the reaction of a cyclic carbonate, a compound having two or more thiol groups, and a compound having two or more amine functional groups. In addition, a method of adhesively binding two or more substrates using the cross-linked composition is provided.

  18. Poly(hydroxyl urethane) compositions and methods of making and using the same

    SciTech Connect

    Luebke, David; Nulwala, Hunaid; Tang, Chau

    2014-12-16

    Methods and compositions relating to poly(hydroxyl urethane) compounds are described herein that are useful as, among other things, binders and adhesives. The cross-linked composition is achieved through the reaction of a cyclic carbonate, a compound having two or more thiol groups, and a compound having two or more amine functional groups. In addition, a method of adhesively binding two or more substrates using the cross-linked composition is provided.

  19. Tertiary aralkyl urethanes and isocyanates derived therefrom

    SciTech Connect

    Singh, B.; Chang, L.W.; Forgione, P.S.

    1984-03-27

    Production of tertiary aralkyl isocyanates, such as tetramethyl xylylene diisocyanates, by thermal cracking of corresponding urethanes formed by addition of corresponding olefins and carbamic acid esters at moderate temperatures and in the presence of acid catalyst.

  20. The metabolism of urethane and related compounds

    PubMed Central

    Boyland, E.; Nery, R.

    1965-01-01

    1. Urethane is metabolized in the rat, rabbit and man by a process of N-hydroxylation. This occurs to a smaller extent when methyl, n-propyl and n-butyl carbamates are administered to the rat and rabbit. 2. Other metabolites which have been detected in urine of animals dosed with urethane and N-hydroxyurethane are ethylmercapturic acid, ethylmercapturic acid sulphoxide and N-acetyl-S-carbethoxycysteine. 3. Substances which appear to be S-ethylglutathione and S-ethylglutathione sulphoxide have been detected in the bile of rats dosed with urethane or N-hydroxyurethane. 4. Methyl, ethyl, n-propyl and n-butyl N-hydroxycarbamates are excreted unchanged in the urine of rats dosed with these compounds to extents depending on the dose administered. 5. Animals dosed with methyl, ethyl, n-propyl or n-butyl carbamate or the corresponding N-hydroxycarbamate excrete the corresponding carbamate and N-hydroxycarbamate in the urine. 6. Methyl, n-propyl and n-butyl carbamates and N-hydroxycarbamates are excreted more slowly than are urethane and N-hydroxyurethane. 7. The probable role of N-hydroxyurethane and the processes of alkylation and carbethoxylation, and of hydroxylamine, nitroxyl and hyponitrous acid in carcinogenesis and chemotherapy with urethane, have been discussed. PMID:14342230

  1. Reactive Fluorescent Dyes For Urethane Coatings

    NASA Technical Reports Server (NTRS)

    Willis, Paul B.; Cuddihy, Edward F.

    1991-01-01

    Molecules of fluorescent dyes chemically bound in urethane conformal-coating materials to enable nondestructive detection of flaws in coats through inspection under ultraviolet light, according to proposal. Dye-bonding technique prevents outgassing of dyes, making coating materials suitable for use where flaw-free coats must be assured in instrumentation or other applications in which contamination by outgassing must be minimized.

  2. Metal-Filled Adhesives Amenable To X-Ray Inspection

    NASA Technical Reports Server (NTRS)

    Hermansen, Ralph D.; Sutherland, Thomas H.; Predmore, Roamer

    1994-01-01

    Adhesive joints between metal parts made amenable to nondestructive radiographic inspection by incorporating radiopaque fillers that increase x-ray contrasts of joints. Adhesives can be epoxies, urethanes, acrylics, phenolics, or silicones, with appropriate curing agents and with such modifiers as polysulfides, polyamides, or butadiene rubbers.

  3. Urethane anesthesia blocks the development and expression of kindled seizures

    SciTech Connect

    Cain, D.P.; Raithby, A.; Corcoran, M.E.

    1989-01-01

    The effect of anesthetic and subanesthetic doses of urethane on the development of amygdala kindled seizures and on the expression of previously kindled seizures was studied in hooded rats. An anesthetic dose of urethane almost completely eliminated evoked after discharge and completely eliminated convulsive behavior in both groups. It also eliminated the seizure response to pentylenetetrazol. Subanesthetic doses of urethane strongly attenuated the expression of previously kindled seizures. These results suggest that urethane may not be an appropriate anesthetic for the study of epileptiform phenomena.

  4. Urethane as an inhibitor of the firefly light reaction

    SciTech Connect

    Nehls, S.M.; Bittar, E.E. )

    1989-01-01

    A study has been made to test the hypothesis that general anesthetics such as urethane are able to inhibit light from a firefly reaction mixture. Urethane was found to reduce light emission in a dose-dependent manner, the minimal effective concentration being about 20 mM. Dixon plots gave a Ki value in the range of 175 to 215 mM. Lineweaver-Burk plots showed that urethane increases the apparent Km for ATP and reduces V{sub max} for the reaction. This is taken to mean that urethane acts as both a competitive and noncompetitive inhibitor of the firefly light reaction (mixed-type inhibition).

  5. Modification of poly(ether urethane) with fluorinated phosphorylcholine polyurethane for improvement of the blood compatibility.

    PubMed

    Tan, Dongsheng; Zhang, Xiaoqing; Li, Jiehua; Tan, Hong; Fu, Qiang

    2012-02-01

    In order to improve the blood compatibility, poly(ether urethane) (PEU) and fluorinated phosphorylcholine polyurethane (P-HFPC) were used to prepare PU/P-HFPC blends by solution mixing. The hemocompatibility in vitro was evaluated with protein adsorption and platelet-rich plasma (PRP) contact tests. It was found that the amount of adsorbed protein on surface was decreased by 87%, and almost no platelet adhesion and activation was observed on the surface of blends when P-HFPC content was above 5 wt %. After adding P-HFPC, the blends basically kept favorable mechanical properties of PEU though the content of P-HFPC rises to 20 wt %. To better understand the relationship between structure and properties, the phase structure and surface property of the blend films were further investigated via differential scanning calorimetry, dynamic mechanical analysis, atomic force microscopy, X-ray photoelectron spectroscopy, and contact angle measurements. The results indicated that the fluorinated phosphorylcholine units could be easily enriched on the surface of blend films due to the phase separation between the PEU and P-HFPC. Therefore, ordinary poly(ether urethane)s can obtain both satisfactory blood compatibility and good mechanical properties just by blending with small amount of P-HFPC. PMID:22083794

  6. Shuttle active thermal control system development testing. Volume 7: Improved radiator coating adhesive tests

    NASA Technical Reports Server (NTRS)

    Reed, M. W.

    1973-01-01

    Silver/Teflon thermal control coatings have been tested on a modular radiator system projected for use on the space shuttle. Seven candidate adhesives have been evaluated in a thermal vacuum test on radiator panels similar to the anticipated flight hardware configuration. Several classes of adhesives based on polyester, silicone, and urethane resin systems were tested. These included contact adhesives, heat cured adhesives, heat and pressure cured adhesives, pressure sensitive adhesives, and two part paint on or spray on adhesives. The coatings attached with four of the adhesives, two silicones and two urethanes, had no changes develop during the thermal vacuum test. The two silicone adhesives, both of which were applied to the silver/Teflon as transfer laminates to form a tape, offered the most promise based on application process and thermal performance. Each of the successful silicone adhesives required a heat and pressure cure to adhere during the cryogenic temperature excursion of the thermal-vacuum test.

  7. URETHANE AFFECTS THE RAT VISUAL SYSTEM AT SUBANESTHETIC DOSES

    EPA Science Inventory

    Urethane is an anesthetic which is commonly used in neurophysiological studies because it is presumed to have minimal effects upon neuronal activity. The study investigated the influence of urethane anesthesia upon flash evoked potentials (FEPs) recorded from hooded rats. 1 suban...

  8. 40 CFR 721.10524 - Fluorinated alkylsulfonamidol urethane polymer (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... polymer (generic). 721.10524 Section 721.10524 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10524 Fluorinated alkylsulfonamidol urethane polymer (generic). (a... generically as fluorinated alkylsulfonamidol urethane polymer (PMN P-11-384) is subject to reporting...

  9. 40 CFR 721.10524 - Fluorinated alkylsulfonamidol urethane polymer (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... polymer (generic). 721.10524 Section 721.10524 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.10524 Fluorinated alkylsulfonamidol urethane polymer (generic). (a... generically as fluorinated alkylsulfonamidol urethane polymer (PMN P-11-384) is subject to reporting...

  10. Nanohydroxyapatite/poly(ester urethane) scaffold for bone tissue engineering.

    PubMed

    Boissard, C I R; Bourban, P-E; Tami, A E; Alini, M; Eglin, D

    2009-11-01

    Biodegradable viscoelastic poly(ester urethane)-based scaffolds show great promise for tissue engineering. In this study, the preparation of hydroxyapatite nanoparticles (nHA)/poly(ester urethane) composite scaffolds using a salt-leaching-phase inverse process is reported. The dispersion of nHA microaggregates in the polymer matrix were imaged by microcomputed X-ray tomography, allowing a study of the effect of the nHA mass fraction and process parameters on the inorganic phase dispersion, and ultimately the optimization of the preparation method. How the composite scaffold's geometry and mechanical properties change with the nHA mass fraction and the process parameters were assessed. Increasing the amount of nHA particles in the composite scaffold decreased the porosity, increased the wall thickness and consequently decreased the pore size. The Young's modulus of the poly(ester urethane) scaffold was improved by 50% by addition of 10 wt.% nHA (from 0.95+/-0.5 to 1.26+/-0.4 MPa), while conserving poly(ester urethane) viscoelastic properties and without significant changes in the scaffold macrostructure. Moreover, the process permitted the inclusion of nHA particles not only in the poly(ester urethane) matrix, but also at the surface of the scaffold pores, as shown by scanning electron microscopy. nHA/poly(ester urethane) composite scaffolds have great potential as osteoconductive constructs for bone tissue engineering. PMID:19442765

  11. Comparative blood compatibility of polyether vs polycarbonate urethanes by epifluorescent video microscopy.

    PubMed

    Mizumoto, D; Nojiri, C; Inomata, Y; Onishi, M; Waki, M; Kido, T; Sugiyama, T; Senshu, K; Uchida, K; Sakai, K; Akutsu, T

    1997-01-01

    The segmented polyether urethanes (PEUs) have been used in implantable medical devices due to excellent mechanical properties, acceptable blood compatibility, and good biostability. However, recent studies demonstrate that the polyether soft segment of PEU is susceptible to oxidative degradation in vivo due to scission of the polyether group. Recently, polycarbonate urethanes (PCUs) having no ether linkage in the soft segment have been developed, and show improved stability against oxidative degradation over PEUs. The current study evaluates blood compatibility of these PCUs in comparison with PEUs using epifluorescent video microscopy (EVM) combined with a parallel plate flow cell. The authors selected two PCUs, Corethane 80A (Corvita Corporation, Miami, FL) and PCU(1560), and two PEUs, Pellethene 2363-80AE (Dow Chemical Japan, Tokyo, Japan) and Tecoflex EG80A (Thermedics, Inc., Woburn, MA), all of which have similar hard segment compositions (MDI or HMDI:1,4-butanediol(BD)) and the same hardness of 80A. The EVM measured the amount of platelet coverage on the surfaces using human whole blood perfused at a wall shear rate of 100/sec for 20 min. Complement activation (C3a) also was measured. Both PEUs, especially Pellethane, showed significantly higher platelet adhesion than the PCUs (p < 0.05). There were no significant differences in platelet adhesion between the two PCUs. As for C3a measurements, Tecoflex showed higher complement activation than the others. Based on these results, it is recommended that PEUs should be replaced by ether free PCUs for use in implantable blood contacting devices such as artificial hearts and pacemaker lead insulators. PMID:9360093

  12. Microstructure property relationships of urethane magnetorheological elastomers

    NASA Astrophysics Data System (ADS)

    Boczkowska, Anna; Awietjan, Stefan F.; Wroblewski, Rafal

    2007-10-01

    Studies on the structure of urethane magnetorheological elastomers (MREs), with respect to their magnetic and mechanical properties, are reported. MREs were obtained from a mixture of polyurethane gel and carbonyl-iron particles cured in a magnetic field of 100 and 300 mT. Samples with different numbers of particles (1.5, 11.5 and 33 vol%) were produced. The microstructure and magnetic properties of the obtained MREs were studied. Also, the displacement of the samples in an external magnetic field was examined using a specially designed experimental set-up. The influences of the number of ferromagnetic particles and their arrangement in relation to the external magnetic field were investigated. It was found that the microstructure of the MREs depends on the number of ferrous particles and the fabrication conditions. The orientation of the iron particles into aligned chains is possible for a lower volume content of the ferromagnetic fillers. The high carbonyl-iron volume content in the matrix leads to the formation of more complex microstructures, similar to three-dimensional lattices. The magnetic measurements also confirmed the existence of the microstructure anisotropy for the MREs with 1.5 and 11.5 vol% of iron particles. The structural and magnetic anisotropy has not been found in the MREs with 33 vol% of Fe. To evaluate the effect of the external magnetic field on the magnetorheological properties, the displacement under magnetic field, the compressive strength, and the rheological properties were measured. The experiments showed that both the particle content and the field strength used during curing have a significant effect on the microstructure of the MREs and, in consequence, on their properties.

  13. Syntheses and properties of elastic copoly(ester-urethane)s containing a phospholipid moiety and the fabrication of nanosheets.

    PubMed

    Sirithep, Wariya; Morita, Kohei; Iwano, Atsushi; Komachi, Takuya; Okamura, Yosuke; Nagase, Yu

    2014-01-01

    In these years, we have investigated the syntheses of novel diamine and diol monomers containing phosphorylcholine (PC) group to obtain biocompatible polymers, the backbone components of which were thermally stable and mechanically strong. In this study, the preparations of elastic copoly(ester-urethane)s containing PC group and polycarbonate segment were carried out by polycondensation and polyaddition using a diol monomer containing PC group and polycarbonate diol. It was found that the obtained polymers exhibited the high-thermal stability up to 200 °C and the elasticity derived from the soft segment. The introduction of PC group was effective to improve the resistance to the adhesions of proteins and platelets on the polymer films, which was the result of surface properties derived from the PC moiety. In addition, we tried to prepare ultra-thin polymer films composed of copoly(ester-urethane)s, so-called nanosheets. As a result, the desired nanosheets were successfully fabricated and the obtained nanosheets exhibited the high adhesive strength, indicating that the nanosheets could conform closely to the desired surfaces due to their exquisite flexibility and low roughness. PMID:24954066

  14. Poly(ester urethane)s consisting of poly[(R)-3-hydroxybutyrate] and poly(ethylene glycol) as candidate biomaterials: characterization and mechanical property study.

    PubMed

    Li, Xu; Loh, Xian Jun; Wang, Ke; He, Chaobin; Li, Jun

    2005-01-01

    Poly(ester urethane)s with poly[(R)-3-hydroxybutyrate] (PHB) as the hard and hydrophobic segment and poly(ethylene glycol) (PEG) as the soft and hydrophilic segment were synthesized from telechelic hydroxylated PHB (PHB-diol) and PEG using 1,6-hexamethylene diisocyanate as a nontoxic coupling reagent. Their chemical structures and molecular characteristics were studied by gel permeation chromatography, 1H NMR, and Fourier transform infrared spectroscopy. Results of differential scanning calorimetry and X-ray diffraction indicated that the PHB segment and PEG segment in the poly(ester urethane)s formed separate crystalline phases with lower crystallinity and a lower melting point than those of their corresponding precursors, except no PHB crystalline phase was observed in those with a relatively low PHB fraction. Thermogravimetric analysis showed that the poly(ester urethane)s had better thermal stability than their precursors. The segment compositions were calculated from the two-step thermal decomposition profiles, which were in good agreement with those obtained from 1H NMR. Water contact angle measurement and water swelling analysis revealed that both surface hydrophilicity and bulk hydrophilicity of the poly(ester urethane)s were enhanced by incorporating the PEG segment into PHB polymer chains. The mechanical properties of the poly(ester urethane)s were also assessed by tensile strength measurement. It was found that the poly(ester urethane)s were ductile, while natural source PHB is brittle. Young's modulus and the stress at break increased with increasing PHB segment length or PEG segment length, whereas the strain at break increased with increasing PEG segment length or decreasing PHB segment length. PMID:16153114

  15. Extending the service life of urethane fuel tanks. Final report

    SciTech Connect

    Gatza, P.E.; Touchet, P.; Feuer, H.O.; Teets, A.R.

    1992-03-01

    This report covers the development of an extraction/immersion test procedure for screening of candidate urethane-coated fabrics, used in collapsible fuel storage tanks. Also included are recommended changes in materials requirements for two military specifications which govern procurement of these tanks.

  16. Reaction of urethane with nucleic acids in vivo

    PubMed Central

    Boyland, E.; Williams, K.

    1969-01-01

    1. [1-14C]Ethyl carbamate, ethyl [carboxy-14C]carbamate, [1-14C]ethanol and sodium hydrogen [14C]carbonate were injected intraperitoneally into C57 mice, and nucleic acids and proteins were separated from the liver and lungs with phenol as described by Kirby (1956). 2. Chromatographic analysis of the hydrolytic products of the urethane-labelled RNA showed the presence of a single radioactive compound differing in behaviour from the major pyrimidine nucleotides and purines. 3. The products from RNA labelled by [1-14C]ethyl carbamate or ethyl [carboxy-14C]carbamate appeared chromatographically identical but could not be detected in the RNA of mice given [1-14C]ethanol or sodium hydrogen [14C]-carbonate. 4. The labelled product appeared to be the ethyl ester of cytosine-5-carboxylic acid formed by the reaction of urethane with RNA in vivo. 5. A direct reaction between labelled urethane or the labelled metabolite of urethane, [1-3H]-ethyl N-hydroxycarbamate, and RNA was not detected. PMID:5775685

  17. Electrospinning of novel biodegradable poly(ester urethane)s and poly(ester urethane urea)s for soft tissue-engineering applications.

    PubMed

    Caracciolo, Pablo C; Thomas, Vinoy; Vohra, Yogesh K; Buffa, Fabián; Abraham, Gustavo A

    2009-10-01

    The development of biomimetic highly-porous scaffolds is essential for successful tissue engineering. Segmented poly(ester urethane)s and poly(ester urethane urea)s have been infrequently used for the fabrication of electrospun nanofibrous tissues, which is surprising because these polymers represent a very large variety of materials with tailored properties. This study reports the preparation of new electrospun elastomeric polyurethane scaffolds. Two novel segmented polyurethanes (SPU), synthesized from poly(epsilon-caprolactone) diol, 1,6-hexamethylene diisocyanate, and diester-diphenol or diurea-diol chain extenders, were used (Caracciolo et al. in J Mater Sci Mater Med 20:145-155, 2009). The spinnability and the morphology of the electrospun SPU scaffolds were investigated and discussed. The electrospinning parameters such as solution properties (polymer concentration and solvent) and processing parameters (applied electric field, needle to collector distance and solution flow rate) were optimized to achieve smooth, uniform bead-free fibers with diameter (~700 nm) mimicking the protein fibers of native extracellular matrix (ECM). The obtained elastomeric polyurethane scaffolds could be appropriate for soft tissue-engineering applications. PMID:19434481

  18. Grafting sulfobetaine monomer onto the segmented poly(ether-urethane) surface to improve hemocompatibility.

    PubMed

    Yuan, Y L; Ai, F; Zhang, J; Zang, X B; Shen, J; Lin, S C

    2002-01-01

    Polyurethanes are widely used as blood-contacting biomaterials, due to their good biocompatibility and mechanical properties. Nevertheless, their blood compatibility is still not adequate for more demanding applications. Surface modification is an effective way to improve the hemocompatibility for biomaterials. The purpose of the present study was to synthesize a novel nonthrombogenic biomaterial by modifying the surface of polyurethane. Ozonization was used to introduce active peroxide groups onto the segmented poly(ether-urethane) (SPEU) film surface and graft polymerization of N,N'-dimethyl (methacryloyloxyethyl) ammonium propanesulfonate (DMAPS), a sulfobetaine structure, onto the ozone-activated SPEU surface was conducted. The SPEU-g-PDMAPS film was characterized by ATR-FTIR, XPS, and contact angle measurements. ATR-FTIR and XPS confirmed the graft polymerization. The grafted film possessed a relatively hydrophilic surface, as revealed by contact angle measurement. The blood compatibility of the grafted films was evaluated by a platelet-rich plasma (PRP) adhesion study and scanning electron microscopy, using SPEU film as the reference. No platelet adhesion was observed for the grafted films incubated with PRP at 37 degrees C for 60 and 180 min. This new sulfobetaine structure grafted biomaterial might have potential for biomedical applications. PMID:12484485

  19. Tailoring the degradation kinetics of poly(ester carbonate urethane)urea thermoplastic elastomers for tissue engineering scaffolds.

    PubMed

    Hong, Yi; Guan, Jianjun; Fujimoto, Kazuro L; Hashizume, Ryotaro; Pelinescu, Anca L; Wagner, William R

    2010-05-01

    Biodegradable elastomeric scaffolds are of increasing interest for applications in soft tissue repair and regeneration, particularly in mechanically active settings. The rate at which such a scaffold should degrade for optimal outcomes, however, is not generally known and the ability to select from similar scaffolds that vary in degradation behavior to allow such optimization is limited. Our objective was to synthesize a family of biodegradable polyurethane elastomers where partial substitution of polyester segments with polycarbonate segments in the polymer backbone would lead to slower degradation behavior. Specifically, we synthesized poly(ester carbonate)urethane ureas (PECUUs) using a blended soft segment of poly(caprolactone) (PCL) and poly(1,6-hexamethylene carbonate) (PHC), a 1,4-diisocyanatobutane hard segment and chain extension with putrescine. Soft segment PCL/PHC molar ratios of 100/0, 75/25, 50/50, 25/75, and 0/100 were investigated. Polymer tensile strengths varied from 14 to 34 MPa with breaking strains of 660-875%, initial moduli of 8-24 MPa and 100% recovery after 10% strain. Increased PHC content was associated with softer, more distensible films. Scaffolds produced by salt leaching supported smooth muscle cell adhesion and growth in vitro. PECUU in aqueous buffer in vitro and subcutaneous implants in rats of PECUU scaffolds showed degradation slower than comparable poly(ester urethane)urea and faster than poly(carbonate urethane)urea. These slower degrading thermoplastic polyurethanes provide opportunities to investigate the role of relative degradation rates for mechanically supportive scaffolds in a variety of soft tissue repair and reconstructive procedures. PMID:20188411

  20. Anaerobic adhesives and sealants. January 1970-December 1987 (citations from the US Patent data base). Report for January 1970-December 1987

    SciTech Connect

    Not Available

    1987-12-01

    This bibliography contains citations of selected patents concerning anaerobically curable adhesive compositions and sealants. Polymethacrylate, and urethane-based compounds are among those discussed. Pressure-sensitive anaerobic adhesives, and bonding methods are included. (This updated bibliography contains 115 citations, 22 of which are new entries to the previous edition.)

  1. Urethane tetrathiafulvalene derivatives: synthesis, self-assembly and electrochemical properities

    PubMed Central

    Sun, Xiang; Lai, Guoqiao; Li, Zhifang; Ma, Yuwen; Yuan, Xiao; Shen, Yongjia

    2015-01-01

    Summary This paper reports the self-assembly of two new tetrathiafulvalene (TTF) derivatives that contain one or two urethane groups. The formation of nanoribbons was evidenced by scanning electron microscopy (SEM) and X-ray diffraction (XRD), which showed that the self-assembly ability of T 1 was better than that of T 2. The results revealed that more urethane groups in a molecule did not necessarily instigate self-assembly. UV–vis and FTIR spectra were measured to explore noncovalent interactions. The driving forces for self-assembly of TTF derivatives were mainly hydrogen bond interactions and π–π stacking interactions. The electronic conductivity of the T 1 and T 2 films was tested by a four-probe method. PMID:26734083

  2. Thermal resistance of composite panels containing superinsulation and urethane foam

    SciTech Connect

    Wilkes, K.E.; Graves, R.S.; Childs, K.W.

    1996-09-01

    Laboratory data are presented on the thermal resistance of composite panels that incorporate superinsulation embedded in urethane foam. Composite panels were fabricated using four types of advanced insulations (three types of evacuated panel superinsulation and one type of gas-filled panel), and three foam blowing agents (CFC-11, HCFC-141b, and HCFC-142b/22 blend). Panels were also fabricated with only the urethane foam to serve as a baseline. Thermal measurements were performed using an ASTM C 518 Heat Flow Meter Apparatus. The thermal resistances of the panels were measured over a two-year period to detect whether any significant changes occurred. A computer model was used to analyze the data, adjusting for differences in size of the advanced insulations, and extrapolating to different sizes of composite panels.

  3. Characterization, biodegradability and blood compatibility of poly[(R)-3-hydroxybutyrate] based poly(ester-urethane)s.

    PubMed

    Liu, Qiaoyan; Cheng, Shaoting; Li, Zibiao; Xu, Kaitian; Chen, Guo-Qiang

    2009-09-15

    Poly(ester-urethane)s (PUs) were synthesized using hexamethylene diisocyanate (HDI) or toluene diisocyanate (TDI) to join short chains (M(n) = 2000) of poly(R-3-hydroxybutyrate) (PHB) diols and poly(epsilon-caprolactone) (PCL) diols with different feed ratios under different reaction conditions. The multiblock copolymers were characterized by nuclear magnetic resonance spectrometer (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), X-ray diffraction (XRD), and scanning electron microscope (SEM). XRD spectra and second DSC heat thermograms of the multiblock copolymers revealed that the crystallization of both PHB and PCL segments was mutually restricted, and, especially, the PCL segment limited the cold crystallization of the PHB segment. The SEM of platelet adhesion experiments showed that the hemocompatibility was affected to some extent by the chain flexibility of the polymers. Hydrolysis studies demonstrated that the hydrolytic degradation of PUs was generated from the scission of their ester bonds or/and urethane bonds. Simultaneously, the rate of ester bond scission was determined to some extent by the crystallization degree, which was further affected by the configuration of polymer chains. These highly elastic multiblock copolymers combining hemocompatibility and biodegradability may be developed into blood contact implant materials for biomedical applications. PMID:18671259

  4. Block poly(ester-urethane)s based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) and poly(3-hydroxyhexanoate-co-3-hydroxyoctanoate).

    PubMed

    Chen, Zhifei; Cheng, Shaoting; Xu, Kaitian

    2009-04-01

    A series of block poly(ester-urethane) poly(3/4HB-HHxHO) urethanes (abbreviated as PUHO) based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB-diol) and poly(3-hydroxyhexanoate-co-3-hydroxyoctanoate) (PHHxHO-diol) segments were synthesized by a facile way of melting polymerization using 1,6-hexamethylene diisocyanate (HDI) as the coupling agent, with different 3HB, 4HB, HHxHO compositions and segment lengths. The chemical structure, molecular weight and distribution were systematically characterized by (1)H, (13)C nuclear magnetic resonance spectrum (NMR), two-dimensional correlation spectroscopy (COSY ((1)H, (13)C) NMR), Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The thermal property was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The hydrophilicity was investigated by static contact angle of water and CH(2)I(2). DSC revealed that the poly(3/4HB-HHxHO) urethanes are almost amorphous with a little crystallinity (less than 6%) and T(g) from -23 degrees C to -3 degrees C. The polyurethanes are more hydrophobic (water contact angle 88 degrees -117 degrees ) than the P3/4HB and PHHxHO raw materials. The lactate dehydrogenase (LDH) assay and platelet adhesion determination showed that the obtained polyurethanes have much higher platelet adhesion property than raw materials and common biodegradable polymers polylactic acid (PLA) and poly(3-hydroxybutyrate) (PHB). Hydrophobicity and crystallinity degree are important factors to affect the platelet adhesion. All the properties can be tailored by changing the composition and segment length of prepolymers P3/4HB-diol and PHHxHO-diol. PMID:19167751

  5. Development of urethane coating and potting material with improved hydrolytic and oxidative stability

    NASA Technical Reports Server (NTRS)

    Morris, D. E.

    1981-01-01

    A series of saturated hydrocarbon based urethanes was prepared and characterized for hydrolytic and oxidative stability. A series of ether based urethanes was used as a basis for comparison. The alkane base urethanes were found to be hydrolytically and oxidatively stable and had excellent electrical properties. The alkane based materials absorbed little or no water and were reversion resistant. There was little loss in hardness or weight when exposed to high temperature and humidity. Dielectric properties were excellent and suffered little adverse effects from the high temperature/humidity conditions. The alkane based urethanes were not degraded by ozone exposure.

  6. Curing Behaviors of UV-Curable Temporary Adhesives for a 3D Multichip Package Process

    NASA Astrophysics Data System (ADS)

    Lee, Seung-Woo; Lee, Tae-Hyung; Park, Ji-Won; Park, Cho-Hee; Kim, Hyun-Joong; Song, Jun-Yeob; Lee, Jae-Hak

    2014-11-01

    Temporary bonding adhesives for a three-dimensional (3D) multichip package process have been synthesized. To enhance the thermal stability, the adhesives used a fluorinated silicon urethane acrylic binder and ultraviolet (UV) curing for crosslinked network structures. Focusing on different photoinitiator contents and UV doses, the UV-curing behaviors and thermal stability were studied using Fourier-transform infrared spectroscopy attenuated total reflectance, gel fraction, swelling ratio, shrinkage, and thermogravimetric analyses.

  7. Lasting glycolytic stress governs susceptibility to urethane-induced lung carcinogenesis in vivo and in vitro.

    PubMed

    Ma, Xiaofang; Deng, Jiaxiu; Cao, Ning; Guo, Zhenzhen; Zheng, Yaqiu; Geng, Shengnan; Meng, Mingjing; Lin, Haihong; Duan, Yongjian; Du, Gangjun

    2016-01-01

    Urethane is a recognized genotoxic carcinogen in fermented foods and beverages. This study is to compare susceptibility of ICR mice, BALB/c mice and C57BL/6 mice to urethane-induced lung carcinogenesis. The mice were injected intraperitoneally with 600 mg/kg of urethane for three times or ten times at 7-day intervals. At week 26, lung carcinogenic incidence was found in 40% ICR mice, 20% BALB/c mice and 10% C57BL/6 mice of the 3× injection group, respectively, whereas 100% lung tumor incidence took place in three mouse strains of the 10× injection group. In the 10× injection group, urethane induced lasting glycolytic stress of lung with an increase in lactate, monocarboxylate transporter 1 (MCT-1), reactive oxygen species(ROS) and 7,8-dihydro-8-oxo-29-deoxyguanosine (8-OHdG) and a decrease in pyruvate dehydrogenase (PDH) and cytochrome C oxidase (COX). In the 3× injection group, urethane also promoted lung glycolytic stress at the end of urethane injection but it lasted no more than 7 days besides in lung tumor-bearing mice. Metformin as a glycolytic enhancer promoted urethane carcinogenic efficacy in the 3× injection group, whereas 2-deoxy-glucose (2-DG) as a glycolytic inhibitor decreased urethane carcinogenic efficacy in the 10× injection group. Further, urethane promoted tumor survival in A549 cells by inducing cancer stem-like cellular state. These data suggest that lasting glycolytic stress is sufficient for urethane-induced lung tumorigenesis, and that urethane 10× injection-induced lung cancer can serve as a valuable model for lung tumor biology and tumor prevention. PMID:26524634

  8. Synthesis and characterization of shape-memory poly carbonate urethane microspheres for future vascular embolization.

    PubMed

    Liu, Rongrong; Dai, Honglian; Zhou, Qian; Zhang, Qian; Zhang, Ping

    2016-08-01

    Two types of shape memory poly carbonate urethanes (PCUs) microspheres were synthesized by pre-polymerization and suspension polymerization, based on Polycarbonate diol (PCDL) as the soft segment, Isophorone diisocyanate (IPDI) and 1,6-hexamethylene diisocyanate (HDI) as the hard segments and 1,4-butanediol (BDO) as the chain expanding agent. The structure, crystallinity, and thermal property of the two synthesized PCUs were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Differential scanning calorimetery (DSC), respectively. The results showed that the two types of PCUs exhibited high thermal stability with phase separation and semi-crystallinity. Also, the results of the compression test displayed that the shape fixity and the shape recovery of two PCUs were more than 90% compared to the originals, indicating their similar bio-applicability and shape-memory properties. The tensile strength, elongation at break was enhanced by introducing and increasing content of HDI. The water contact angles of PCUs decreased and their surface tension increased by surface modified with Bovine serum albumin (BSA). Furthermore, the biological study results of two types of PCUs from the platelet adhesion test and the cell proliferation inhibition test indicated they had some biocompatibilites. Hence, the PCU microspheres might represent a smart and shape-memory embolic agent for vascular embolization. PMID:27193120

  9. Development of Photocrosslinkable Urethane-Doped Polyester Elastomers for Soft Tissue Engineering

    PubMed Central

    Zhang, Yi; Tran, Richard T.; Gyawali, Dipendra; Yang, Jian

    2012-01-01

    Finding an ideal biomaterial with the proper mechanical properties and biocompatibility has been of intense focus in the field of soft tissue engineering. This paper reports on the synthesis and characterization of a novel crosslinked urethane-doped polyester elastomer (CUPOMC), which was synthesized by reacting a previously developed photocrosslinkable poly (octamethylene maleate citrate) (POMC) prepolymers (pre-POMC) with 1,6-hexamethylene diisocyanate (HDI) followed by thermo- or photo-crosslinking polymerization. The mechanical properties of the CUPOMCs can be tuned by controlling the molar ratios of pre-POMC monomers, and the ratio between the prepolymer and HDI. CUPOMCs can be crosslinked into a 3D network through polycondensation or free radical polymerization reactions. The tensile strength and elongation at break of CUPOMC synthesized under the known conditions range from 0.73±0.12MPa to 10.91±0.64MPa and from 72.91±9.09% to 300.41±21.99% respectively. Preliminary biocompatibility tests demonstrated that CUPOMCs support cell adhesion and proliferation. Unlike the pre-polymers of other crosslinked elastomers, CUPOMC pre-polymers possess great processability demonstrated by scaffold fabrication via a thermally induced phase separation method. The dual crosslinking methods for CUPOMC pre-polymers should enhance the versatile processability of the CUPOMC used in various conditions. Development of CUPOMC should expand the choices of available biodegradable elastomers for various biomedical applications such as soft tissue engineering. PMID:23565318

  10. New heparinizable modified poly(carbonate urethane) surfaces diminishing bacterial colonization.

    PubMed

    De Nardo, Luigi; Farè, Silvia; Di Matteo, Valentina; Cipolla, Eliana; Saino, Enrica; Visai, Livia; Speziale, Pietro; Tanzi, Maria Cristina

    2007-11-01

    Percutaneous devices are extensively used in modern medicine therapies, even in long term applications. Complications from their use, related to bacterial colonization and/or to materials thrombogenicity, may result in a significant morbidity and mortality incidence. In this study, a novel polycarbonate-urethane (PCU), incorporating a tailor-made diamino-diamide-diol (PIME) showing the ability to bind heparin at physiological pH, was compared to commercial medical-grade PCUs (Carbothane and Bionate). Mechanical and thermal properties were evaluated by tensile tests, dynamic mechanical analysis and differential scanning calorimetry. The presence of a low amount of PIME chain extender in Bionate polyurethanes (Bionate-PIME) slightly affects the mechanical properties, remaining however comparable with the medical grade PCUs used for the fabrication of cardiovascular devices. To verify thereof heparin surface adsorbed in disfavouring bacterial colonization, heparinized Bionate-PIME was tested for bacterial adhesion, using Bionate and Carbothane as reference. In vitro bacterial interaction tests were performed with the strains mainly involved in the pathogenesis of device-related infections (S. epidermidis and S. aureus). MTT tests and SEM observations showed a decrease in colonization of the different strains on the heparinized Bionate-PIME surfaces, confirming that preadsorbed heparin plays a role in mediating the biomaterial surface/bacterial cells interactions. PMID:17665117

  11. Biodegradable block poly(ester-urethane)s based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymers.

    PubMed

    Ou, Wenfeng; Qiu, Handi; Chen, Zhifei; Xu, Kaitian

    2011-04-01

    A series of block poly(ester-urethane)s (abbreviated as PU3/4HB) based on biodegradable poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB) segments were synthesized by a facile way of melting polymerization using 1,6-hexamethylene diisocyanate (HDI) as the coupling agent and stannous octanoate (Sn(Oct)(2)) as catalyst, with different 4HB contents and segment lengths. The chemical structure, molecular weight and distribution were systematically characterized by (1)H nuclear magnetic resonance spectrum (NMR), Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The thermal property was studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The hydrophilicity was investigated by static contact angle of deionized water and CH(2)I(2). DSC curves revealed that the PU3/4HB polyurethanes have their T(g) from -25.6 °C to -4.3 °C, and crystallinity from 2.5% to 25.3%, being almost amorphous to semi-crystalline. The obtained PU3/4HBs are hydrophobic (water contact angle 77.4°-95.9°), and their surface free energy (SFE) were studied. The morphology of platelets adhered on the polyurethane film observed by scanning electron microscope (SEM) showed that platelets were activated on the PU3/4HB films which would lead to blood coagulation. The lactate dehydrogenase (LDH) assay revealed that the PU3/4HBs displayed higher platelet adhesion property than raw materials and biodegradable polymer polylactic acid (PLA) and would be potential hemostatic materials. Crystallinity degree, hydrophobicity, surface free energy and urethane linkage content play important roles in affecting the LDH activity and hence the platelet adhesion. CCK-8 assay showed that the PU3/4HB is non-toxic and well for cell growth and proliferation of mouse fibroblast L929. It showed that the hydrophobicity is an important factor for cell growth while 3HB content of the PU3/4HB is important for the cell proliferation. Through changing the

  12. Development of modified poly(perfluoropropyleneoxide) urethane systems for use in liquid oxygen and in enriched 100 percent oxygen atmosphere

    NASA Technical Reports Server (NTRS)

    Harrison, E. S.

    1973-01-01

    This program consisted of two separate though related phases. The initial phase was directed toward improving the mechanical and adhesive properties of the very highly fluorinated-polyurethane resin system derived from the hydroxyl-terminated polyperfluoropropylene oxide and 6-chloro-2,4,5-trifluoro-m-phenylene diisocyanate. Various new curing agents for this system were investigated, with the goal of providing a more thermally stable crosslink (cure) mechanism to provide wider applicability and fuller utilization of the outstanding oxygen resistance of the PFPO system. Complete resistance to liquid- and gaseous-oxygen impact at presures as high as 1035 N/sq cm were attained with the use of the PFPO resin castings. The second corollary phase was directed toward investigating the feasibility and optimization of the allophanate cured, urethane extended polymer derived from hydroxyl-terminated polyperfluoropropyleneoxide and 6-chloro-2,4,5-trifluoro-m-phenylene diisocyanate, as the adhesive system for use in a weld-bond configuration for liquid oxygen tankage. The synthesis and application procedures of the adhesive system to insure liquid oxygen compatibility (under 10 kg-m loading), and the development of procedures and techniques to provide high quality weld-bonded joint configurations were studied.

  13. Evaluation of urethane for feasibility of use in wind turbine blade design

    NASA Technical Reports Server (NTRS)

    Lieblein, S.; Ross, R. S.; Fertis, D. G.

    1979-01-01

    A preliminary evaluation was conducted of the use of cast urethane as a possible material for low-cost blades for wind turbines. Specimen test data are presented for ultimate tensile strength, elastic modulus, flexural strain, creep, and fatigue properties of a number of urethane formulations. Data are also included for a large-scale urethane blade section composed of cast symmetrical half-profiles tested as a cantilever beam. Based on these results, an analysis was conducted of a full-scale blade design of cast urethane that meets the design specifications of the rotor blades for the NASA/DOE experimental 100-kW MOD-0 wind turbine. Because of the low value of elastic modulus for urethane (around 457 000 psi), the design loads would have to be carried by metal reinforcement. Considerations for further evaluation are noted.

  14. Comparison of surface modification of poly(ether urethanes) on physical properties and blood compatibility

    SciTech Connect

    Wrobleski, D.A.; Cash, D.L.; Hermes, R.E.

    1988-01-01

    Because of their good elastomeric properties including the ability to undergo repeated flexing without failure, polyurethanes are used in a number of biomedical applications including flexing diaphragms or coatings on surfaces in artificial hearts and heart assist devices. In particular, the poly(ether urethanes), are preferred for use in biomedical applications because of their greater hydrolytic stability as compared to poly(ester urethanes). However, poly(ether urethanes), as other polymeric materials in contact with blood, cause formation of thrombus and bacterial infections. These problems might be overcome by incorporation of antithrombogenic substances and/or antibacterial agents in the surface of the polymer. We have explored both of these methods by examining the infusion of polyvinylpyrrolidone (PVP) and poly(ethylene glycol) (PEG) into commercially available poly(ether urethanes) and the graft polymerization of N-vinyl pyrrolidone onto poly(ether urethanes). Preliminary results are presented here. 7 refs., 1 fig.

  15. Abdominal Adhesions

    MedlinePlus

    ... Abdominal Adhesions 1 Ward BC, Panitch A. Abdominal adhesions: current and novel therapies. Journal of Surgical Research. 2011;165(1):91– ... are abdominal adhesions and intestinal obstructions ... generally do not require treatment. Surgery is the only way to treat abdominal ...

  16. Synthesis and evaluation of a novel co-initiator for dentin adhesives: polymerization kinetics and leachables study

    PubMed Central

    Ge, Xueping; Ye, Qiang; Song, Linyong; Laurence, Jennifer S.; Spencer, Paulette

    2015-01-01

    A new tertiary amine co-initiator (TUMA) containing three methacrylate-urethane groups was synthesized for application in dentin adhesives. The photopolymerization kinetics and leaching of unreacted components from methacrylate-based dental polymers formulated with this new co-initiator were determined. The newly synthesize co-initiator showed good chemical stability and decreased amine release from the initiator system. This study provides important information for the future development of biocompatible dentin adhesives/composites. PMID:26052187

  17. Synthesis and Evaluation of a Novel Co-Initiator for Dentin Adhesives: Polymerization Kinetics and Leachables Study

    NASA Astrophysics Data System (ADS)

    Ge, Xueping; Ye, Qiang; Song, Linyong; Laurence, Jennifer S.; Spencer, Paulette

    2015-04-01

    A new tertiary amine co-initiator containing three methacrylate-urethane groups was synthesized for the application in dentin adhesives. The photopolymerization kinetics and leaching of unreacted components from methacrylate-based dental polymers formulated with this new co-initiator were determined. The newly synthesized co-initiator showed good chemical stability and decreased amine release from the initiator system. This study provides important information for the future development of biocompatible dentin adhesives/composites.

  18. Synthesis, characterization and cell compatibility of novel poly(ester urethane)s based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) prepared by melting polymerization.

    PubMed

    Chen, Zhifei; Cheng, Shaoting; Li, Zibiao; Xu, Kaitian; Chen, Guo-Qiang

    2009-01-01

    Novel tailor-made poly(ester urethane)s (PUs) based on microbial polyesters poly(3-hydroxybutyrate-co-4hydroxybutyrate) (P3HB4HB) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) were synthesized by melting polymerization (MP) using 1,6-hexamethylene diisocyanate (HDI) as a coupling agent. A comprehensive characterization using (1)H-NMR, Fourier transform infrared spectroscopy (FT-IR), gel-permeation chromatography (GPC), differential scanning calorimetry (DSC), mechanical properties, static water contact angles, cell proliferation using smooth muscle cells from rabbit aorta (RaSMCs) and immortalized human keratinocytes (HaCat), and blood coagulation behavior were conducted on the synthesized PUs films. DSC showed that PU samples had a low degree of crystallinity at room temperature and became fully amorphous after a melt-quenched process. The series of tailor-made PUs based on different mass ratios of P3HB4HB and PHBHHx revealed a ductile and flexile mechanical property especially for PHBHHx-rich PU, or a hydrophobic property for 4HB-rich PU. A 4 days incubation experiment showed that all PU films had a better cell proliferation than poly(lactic acid) (PLA), polyhydroxybutyrate (PHB), P3HB4HB and PHBHHx. RaSMCs cultured on PU films had a quiescent contractile phenotype, indicating that they were fully functional. HaCat incubated on tailor-made PU films showed a proliferation approximately equal to tissue-culture plates (TCPs). Blood coagulation behavior tests revealed a strong platelet adhesion and a short coagulation time on PU films. This study demonstrated potential medical applications for P3HB4HB and PHBHHx based polyurethane as a hydrophobic wound-healing and hemostatic materials. PMID:19622282

  19. Preparation and properties of an internal mold release for rigid urethane foam

    SciTech Connect

    Parker, B.G.

    1980-08-01

    Internal mold releases which can be added to urethane foam resin were synthesized and evaluated. The use of this type of release agent eliminates the repeated cleaning and recoating of molds, a procedure required with surface-applied mold releases. The internal mold releases investigated are the reaction products of a fatty acid ester, containing an active hydrogen, and a monoisocycanate. The use of an internal mold release resulted in urethane foam with good releasability and excellent surface bondability. Several properties of rigid urethane foam formulated with the use of an internal mold release are presented.

  20. Development of palm oil-based UV-curable epoxy acrylate and urethane acrylate resins for wood coating application

    SciTech Connect

    Tajau, Rida; Mahmood, Mohd Hilmi; Salleh, Mek Zah; Salleh, Nik Ghazali Nik; Ibrahim, Mohammad Izzat; Yunus, Nurulhuda Mohd

    2014-02-12

    The trend of using renewable sources such as palm oil as raw material in radiation curing is growing due to the demand from the market to produce a more environmental friendly product. In this study, the radiation curable process was done using epoxy acrylate and urethane acrylate resins which are known as epoxidised palm olein acrylate (EPOLA) and palm oil based urethane acrylate (POBUA), respectively. The purpose of the study was to investigate curing properties and the application of this UV-curable palm oil resins for wood coating. Furthermore, the properties of palm oil based coatings are compared with the petrochemical-based compound such as ebecryl (EB) i.e. EB264 and EB830. From the experiment done, the resins from petrochemical-based compounds resulted higher degree of crosslinking (up to 80%) than the palm oil based compounds (up to 70%), where the different is around 10-15%. The hardness property from this two type coatings can reached until 50% at the lower percentage of the oligomer. However, the coatings from petrochemical-based have a high scratch resistance as it can withstand at least up to 3.0 Newtons (N) compared to the palm oil-based compounds which are difficult to withstand the load up to 1.0 N. Finally, the test on the rubber wood substrate showed that the coatings containing benzophenone photoinitiator give higher adhesion property and their also showed a higher glosiness property on the glass substrate compared to the coatings containing irgacure-819 photoinitiator. This study showed that the palm oil coatings can be a suitable for the replacement of petrochemicals compound for wood coating. The palm oil coatings can be more competitive in the market if the problems of using high percentage palm oil oligomer can be overcome as the palm oil price is cheap enough.

  1. Development of palm oil-based UV-curable epoxy acrylate and urethane acrylate resins for wood coating application

    NASA Astrophysics Data System (ADS)

    Tajau, Rida; Ibrahim, Mohammad Izzat; Yunus, Nurulhuda Mohd; Mahmood, Mohd Hilmi; Salleh, Mek Zah; Salleh, Nik Ghazali Nik

    2014-02-01

    The trend of using renewable sources such as palm oil as raw material in radiation curing is growing due to the demand from the market to produce a more environmental friendly product. In this study, the radiation curable process was done using epoxy acrylate and urethane acrylate resins which are known as epoxidised palm olein acrylate (EPOLA) and palm oil based urethane acrylate (POBUA), respectively. The purpose of the study was to investigate curing properties and the application of this UV-curable palm oil resins for wood coating. Furthermore, the properties of palm oil based coatings are compared with the petrochemical-based compound such as ebecryl (EB) i.e. EB264 and EB830. From the experiment done, the resins from petrochemical-based compounds resulted higher degree of crosslinking (up to 80%) than the palm oil based compounds (up to 70%), where the different is around 10-15%. The hardness property from this two type coatings can reached until 50% at the lower percentage of the oligomer. However, the coatings from petrochemical-based have a high scratch resistance as it can withstand at least up to 3.0 Newtons (N) compared to the palm oil-based compounds which are difficult to withstand the load up to 1.0 N. Finally, the test on the rubber wood substrate showed that the coatings containing benzophenone photoinitiator give higher adhesion property and their also showed a higher glosiness property on the glass substrate compared to the coatings containing irgacure-819 photoinitiator. This study showed that the palm oil coatings can be a suitable for the replacement of petrochemicals compound for wood coating. The palm oil coatings can be more competitive in the market if the problems of using high percentage palm oil oligomer can be overcome as the palm oil price is cheap enough.

  2. Nanostructured Self-Assembling Systems Based on Functional Poly(Urethane/Siloxane)S

    NASA Astrophysics Data System (ADS)

    Savelyev, Yuri

    Novel hybride organo-inorganic systems based on urethane-, urea-crown ether- and siloxane-containing monomers and oligomers have been developed by sol-gel method. Structure-properties relationships were discussed.

  3. Structure and relaxation dynamics of poly(amide urethane)s with bioactive transition metal acetyl acetonates in hard blocks.

    PubMed

    Kalogeras, I M; Roussos, M; Vassilikou-Dova, A; Spanoudaki, A; Pissis, P; Savelyev, Y V; Shtompel, V I; Robota, L P

    2005-12-01

    Structural characteristics, thermal transitions and molecular dynamics of selected poly(amide urethane)s with transition metal acetyl acetonates Me(AcAc)(2) (Me = Sn(4+), Zn(2+), Cu(2+), Pb(2+)) as chain extenders, were comparatively investigated using small- and wide-angle X-ray scattering (SAXS, WAXS), differential scanning calorimetry (DSC), and dielectric techniques (dielectric relaxation spectroscopy, DRS; thermally stimulated currents, TSC). We studied the influence of metal chelates on the mixing of the soft-segment (SS) and hard-segment (HS) domains and the related degree of microphase separation (DMS). The reactivity of Me(AcAc)(2) with macrodiisocyanate was found to decrease in the order Sn(AcAc)(2)Cl(2) > Cu(AcAc)(2) > Zn(AcAc)(2) > Pb(AcAc)(2). While Pb(AcAc)(2) shows a higher tendency for crystallisation, both the dielectric and calorimetric results suggest that the corresponding polyurethane has comparatively low DMS. The type of the transition metal has moderate effect on the glass transition temperature and no influence on the shape of the dielectric alpha relaxation signal, indicating weak interactions between metal ions and SS domains. In contrast, structural parameters and the dielectric behaviour of the beta relaxation suggest preference for hydrogen-bonding interactions between Sn(4+) and Cu(2+) metal-chelates and HS domains. The temperature dependence of dc conductivity sigma(dc) is described by the Vogel-Tammann-Fulcher equation and signifies the coupling between the mobility of polymeric chains and charges' motion. It may be expected that the present combination of techniques and particular results with respect to DMS will contribute to the development and testing of novel biodegradation-resistant and antibacterial metal-polyurethanes for biotechnological and industrial applications. PMID:16331340

  4. Abdominal Adhesions

    MedlinePlus

    ... Adhesions 1 Ward BC, Panitch A. Abdominal adhesions: current and novel therapies. Journal of Surgical Research. 2011;165(1):91–111. Seek Help for ... and how to participate, visit the NIH Clinical Research Trials and You website ... Foundation for Functional Gastrointestinal Disorders 700 West Virginia ...

  5. Urethane inhibits genioglossal long-term facilitation in un-paralyzed anesthetized rats

    PubMed Central

    Cao, Ying; Ling, Liming

    2010-01-01

    For ~3 decades, urethane has been (partially or solely) used as a successful anesthetic in numerous respiratory long-term facilitation (LTF) studies, which were performed on anesthetized, paralyzed, vagotomized and artificially ventilated animals of several different species. However, things become complicated when LTF of muscle activity is studied in un-paralyzed animals. For example, a commonly used acute intermittent hypoxia (AIH) protocol failed to induce muscle LTF in anesthetized, spontaneously breathing rats. But muscle LTF could be induced when hypoxic episode number was increased and/or anesthetics other than urethane were used. In these studies however, neither anesthetic nor paralysis was mentioned as a potential factor influencing AIH-induced muscle LTF. This study tested whether urethane inhibits AIH-induced genioglossal LTF (gLTF) in un-paralyzed ventilated rats, and if so, determined whether reducing urethane dose reverses this inhibition. Three groups of adult male Sprague-Dawley rats were anesthetized (Group 1: ~1.6 g·kg−1 urethane; Group 2: 50 mg·kg−1 α-chloralose + 0.9–1.2 g·kg−1 urethane; Group 3: 0.9 g·kg−1 urethane + 200–400 µg·kg−1·min−1 alphaxalone), vagotomized and mechanically ventilated. Integrated genioglossus activity was measured before, during and after AIH (5 episodes of 3-min isocapnic 12% O2, separated by 3-min hyperoxic intervals). The AIH-induced gLTF was absent in Group 1 rats (success rate was only ~1/7), but was present in Group 2 (in 10/12 rats) and Group 3 (in 11/11 rats) rats. The genioglossal response to hypoxia was not significantly different among the 3 groups. Collectively, these data suggest that urethane dose-dependently inhibits gLTF in un-paralyzed anesthetized rats. PMID:20433898

  6. Development of low viscosity alkane-based urethane for connector potting applications

    NASA Technical Reports Server (NTRS)

    Morris, D. E.

    1983-01-01

    Two series of saturated hydrocarbon-based urethanes were prepared with isophorone diisocyanate and one series with methyl bis (4-cyclohexyl isocyanate). The urethanes with molecular weights as great as 2500 had viscosities low enough and a working life long enough to be used in potting, molding, and coating applications. Specimens were prepared and mechanical properties such as hardness, tensile strength elongation, and tear strength were determined. Thermomechanical properties (glass transition and expansion coefficient) and thermogravimetric properties were determined.

  7. The Suitability of Propofol Compared with Urethane for Anesthesia during Urodynamic Studies in Rats

    PubMed Central

    Moheban, Adam A; Chang, Huiyi H; Havton, Leif A

    2016-01-01

    Urethane anesthesia preserves many reflex functions and is often the preferred anesthetic for urodynamic studies in rats. Because of the toxicity profile of urethane, its use as an anesthetic typically is limited to acute and terminal investigations. Alternative anesthetic options are needed for longitudinal studies of micturition reflexes in rats. In this study, we evaluated propofol anesthesia administered at constant rate infusion at different planes of anesthesia in rats for combined cystometrography and external urethral sphincter (EUS) EMG in rats. No reflex micturition was noted after rats received 100%, 80%, or 60% of a previously reported anesthetic dose of propofol. At 40% of the standard propofol dose, a subset of rats showed reflex voiding, with bladder contractions and associated EUS EMG activity. In contrast, urethane anesthesia at a surgical plane allowed for reflex voiding with bladder contractions and EUS activation. Latency to leaking or voiding was longer in rats under propofol anesthesia than in those under urethane anesthesia. In a subset of rats with reflex voiding under propofol anesthesia, voiding efficiency was decreased compared with that of rats anesthetized with urethane. We conclude that propofol anesthesia suppresses micturition reflexes in rats more efficiently than did urethane. Propofol is a suitable anesthetic for longitudinal studies in rats, but its use for urodynamic evaluations is limited in these animals due to its marked suppression of both bladder contractions and EUS EMG activation. PMID:26817985

  8. Low-VOC wood floor varnishes from waterborne oil-modified urethanes

    SciTech Connect

    Ingle, D.M.; Petschke, G.H.

    1997-12-31

    Varnishes protect wood flooring and enhance its beauty. Varnish compositions have varied from drying oils and alkyds to more durable systems (moisture-cured urethanes, oil-modified urethanes, epoxies and UV-curable coatings). Some chemistries are better suited for professional or factory applied situations. Oils, alkyds and oil-modified urethanes (OMU) are suitable for onsite professional application or even refinish application by homeowners (DIY market). These materials traditionally have been high in VOC. Recently, waterborne (WB) systems (such as polyurethane dispersions) with greatly reduced VOC have been used; high costs and relatively poor durability are drawbacks. A new generation of high performance waterborne oil-modified urethane is now available with extended shelf-stability required for contractor and consumer markets. Formulated varnishes are coming onto the market that offer performance similar to conventional OMU, but with significant reductions in VOC. For example, a typical formulation for a conventional solvent-borne oil-modified urethane can be supplied at 1.6 lb/gal (less water). This represents a VOC reduction of 70-75% at equal application coating weight. Furthermore, waterborne oil-modified urethane offers advantages over polyurethane dispersions in performance areas such as durability and mar resistance.

  9. Degradation of poly(carbonate urethane) by gamma irradiation

    NASA Astrophysics Data System (ADS)

    Özdemir, T.; Usanmaz, A.

    2007-06-01

    Poly(carbonate urethane) (PCU), is a valuable commercial engineering polymer. In order to understand the possible use of PCU in radioactive waste management as a solidifying agent or as a disposal container, radiation stability of the PCU is studied by Co-60 gamma irradiations at two different dose rates of 1540 and 82.8 Gy/h. The total dose of irradiation was up to 6.24 MGy. Degradation nature was tested by studying the changes in mechanical and thermal properties with rate and total dose of irradiation. Ultimate tensile strength and toughness first increased and then decreased with the irradiation dose. Half value dose (HVD) for elongation was 4010 kGy and for tensile strength 6010 kGy at the dose rate of 1540 Gy/h. The non-irradiated PCU transparent color changed to yellow and then brown with increased irradiation dose. The FTIR spectral analysis showed a random scission of polymer with irradiation. From the experimental observation, it was shown that PCU can be used for embedding radioactive waste for about 300 years.

  10. Phase Separation of Model Segmented Poly(Carbonate Urethanes)

    NASA Astrophysics Data System (ADS)

    Hernandez, Rebeca; Hung, Elena; Runt, James

    2006-03-01

    The present paper focuses on the phase separated morphology and segment demixing of model poly(carbonate urethanes) [PCU] with hard segment contents ranging from 30 -- 65% and soft segments composed of 1,6 poly(hexamethylene carbonate) [MW = 1K]. Hard segments were formed from 4,4'-methylenediphenyl diisocyanate and 1,4 butanediol. This family of materials represents a recent approach in the development of polyurethanes with improved long-term biostability, and is under clinical investigation in a number of biomedical devices. Only a single glass transition temperature was observed for each copolymer, increasing in temperature with increasing hard segment content. However, loss spectra from dynamic mechanical analysis showed clear evidence of two mixed phases. The results of small-angle X-ray scattering and tapping mode AFM experiments were consistent with these observations and will be discussed. Finally, these results will be compared with initial findings on phase separation in another family of polyurethane copolymers of current interest as blood-contact materials in biomedical devices having mixed poly(dimethylsiloxane) -- poly(hexamethyleneoxide) soft segments.

  11. Characterization of the structures of poly(urea-urethane) microcapsules.

    PubMed

    Matsunami, Yuki; Ichikawa, Kimio

    2002-08-21

    A series of poly(urea-urethane) microcapsules containing phthalate derivatives as a core material were prepared by an interfacial polymerization process in order to investigate the structural formation mechanism. Scanning electron microscopy (SEM) analysis for the cross sections of microcapsules revealed the systematic formations of porous structures followed by the formation of core/shell structures. Critical values of the core oil content for the formation of porous and core/shell structures were obtained from SEM results and the critical values were found to be proportional to the solubility parameters of core materials. Dynamic mechanical measurements indicated an amorphous structure of wall membrane and the glass transition temperature was found to decrease with increasing the core oil content suggesting a plasticizing effect. The surface amount of the core oils absorbed in the wall membrane was estimated using time of flight secondary ion spectroscopy analysis and found to increase with increasing the oil content before reaching constant. This tendency was interpreted in terms of the structural formation of the microcapsules. The results obtained in the present investigation were reasonably understood on the basis of swelling theory of wall membrane and the Flory-Huggins interaction parameters of the systems were discussed. PMID:12176237

  12. Shape memory polymers based on uniform aliphatic urethane networks

    SciTech Connect

    Wilson, T S; Bearinger, J P; Herberg, J L; Marion III, J E; Wright, W J; Evans, C L; Maitland, D J

    2007-01-19

    Aliphatic urethane polymers have been synthesized and characterized, using monomers with high molecular symmetry, in order to form amorphous networks with very uniform supermolecular structures which can be used as photo-thermally actuable shape memory polymers (SMPs). The monomers used include hexamethylene diisocyanate (HDI), trimethylhexamethylenediamine (TMHDI), N,N,N{prime},N{prime}-tetrakis(hydroxypropyl)ethylenediamine (HPED), triethanolamine (TEA), and 1,3-butanediol (BD). The new polymers were characterized by solvent extraction, NMR, XPS, UV/VIS, DSC, DMTA, and tensile testing. The resulting polymers were found to be single phase amorphous networks with very high gel fraction, excellent optical clarity, and extremely sharp single glass transitions in the range of 34 to 153 C. Thermomechanical testing of these materials confirms their excellent shape memory behavior, high recovery force, and low mechanical hysteresis (especially on multiple cycles), effectively behaving as ideal elastomers above T{sub g}. We believe these materials represent a new and potentially important class of SMPs, and should be especially useful in applications such as biomedical microdevices.

  13. On imparting radiopacity to a poly(urethane urea).

    PubMed

    James, Nirmala R; Jayakrishnan, A

    2007-07-01

    A poly(urethane urea) (PUU) synthesized from 2,4-toluene diisocyanate (TDI) and polyethylene glycol (PEG) with ethylenediamine (ED) as the chain extender was rendered radiopaque by attaching 3,4,5-triiodobenzoic acid (TIB) onto the polymer backbone. The radiopaque polyurethane obtained was characterized by infra red (IR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-radiography. By optimizing the reaction conditions, it was possible to carry out the modification without adversely affecting the properties of the starting polymer significantly. IR spectral evidence suggested that the hydrogen bonded structure of PUU remained undisrupted even after modification. However, the product exhibited altered thermal characteristics when compared to the parent polymer. Degradation characteristics as observed from the TGA remained unchanged, while one of the glass transitions got shifted to a lower temperature. The observed changes in thermal characteristics were explained on the basis of possible inter-phase mixing and the changes in the close packing of the polymer chains by the introduction of bulky iodine atoms. PMID:17445880

  14. Polymers from amino acids: development of dual ester-urethane melt condensation approach and mechanistic aspects.

    PubMed

    Anantharaj, S; Jayakannan, M

    2012-08-13

    A new dual ester-urethane melt condensation methodology for biological monomers-amino acids was developed to synthesize new classes of thermoplastic polymers under eco-friendly and solvent-free polymerization approach. Naturally abundant L-amino acids were converted into dual functional ester-urethane monomers by tailor-made synthetic approach. Direct polycondensation of these amino acid monomers with commercial diols under melt condition produced high molecular weight poly(ester-urethane)s. The occurrence of the dual ester-urethane process and the structure of the new poly(ester-urethane)s were confirmed by (1)H and (13)C NMR. The new dual ester-urethane condensation approach was demonstrated for variety of amino acids: glycine, β-alanine, L-alanine, L-leucine, L-valine, and L-phenylalanine. MALDI-TOF-MS end group analysis confirmed that the amino acid monomers were thermally stable under the melt polymerization condition. The mechanism of melt process and the kinetics of the polycondensation were studied by model reactions and it was found that the amino acid monomer was very special in the sense that their ester and urethane functionality could be selectively reacted by polymerization temperature or catalyst. The new polymers were self-organized as β-sheet in aqueous or organic solvents and their thermal properties such as glass transition temperature and crystallinity could be readily varied using different l-amino acid monomers or diols in the feed. Thus, the current investigation opens up new platform of research activates for making thermally stable and renewable engineering thermoplastics from natural resource amino acids. PMID:22713137

  15. Biodegradable radiopaque iodinated poly(ester urethane)s containing poly(ε-caprolactone) blocks: synthesis, characterization, and biocompatibility.

    PubMed

    Sang, Lin; Wei, Zhiyong; Liu, Keliang; Wang, Xinhui; Song, Kedong; Wang, Hong; Qi, Min

    2014-04-01

    Biodegradable radiopaque iodinated poly(ester-urethane) (I-PU), consisting of poly(ε-caprolactone) (PCL) diol and iodinated bisphenol A (IBPA), has been successfully synthesized via a coupling reaction of PCL-diisocyanate and IBPA with varying compositions. The IBPA with four iodine atoms per molecule was applied as a chain extender to endow the I-PUs with intrinsic X-ray visibility. The chemical structure and molecular weights of I-PUs were characterized by Fourier transform infrared spectroscopy (FT-IR), proton-nuclear magnetic resonance, and gel permeation chromatography (GPC). The effects of IBPA on the physical properties of I-PUs were systematically studied by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and wide-angle X-ray diffraction (WAXD). The DSC results showed that the crystallization of PCL segments in I-PUs was restrained with increasing amount of IBPA, which was also confirmed by WAXD. In the X-radiography analysis, all the synthesized I-PUs exhibited high radiopacity compared with an aluminum wedge of equivalent thickness. Enzymatic degradation tests showed that the incorporation of IBPA prolonged the degradation of I-PUs and distinct mass loss and degradation happened in the third month. Basic cytocompatibility conducted using rat adipose-derived cells proved that all the I-PUs and their biodegradation products were nontoxic. The radiopaque I-PUs is expected to possess a significant advantage over the traditional polymer counterparts in some related biomedical fields. PMID:23640806

  16. Investigation of non-isocyanate urethane functional latexes and carbon nanofiller/epoxy coatings

    NASA Astrophysics Data System (ADS)

    Meng, Lei

    This dissertation consists of two parts. In the first part, a new class of non-isocyanate urethane methacrylates was synthesized and the effect of the new monomers on the urethane functional latex was investigated. The second part focused on a comparison of carbon nanofillers in inorganic/organic epoxy coating system for anticorrosive applications. A new class of non-isocyanate urethane methacrylates (UMAs) monomers was synthesized through an environmentally friendly non-isocyanate pathway. The kinetics of seeded semibatch emulsion polymerization of UMAs with methyl methacrylate (MMA) and butyl acrylate (BA) was monitored. The particle size and morphology were investigated by dynamic light scattering (DLS), ultrasound acoustic attenuation spectroscopy (UAAS) and transmission electron microscopy (TEM). The minimum film formation temperature (MFFT), mechanical and viscoelastic properties were studied. It was found that the emulsion polymerization processes all proceeded via Smith-Ewart control, leading to the uniform morphology and particle size. The glass transition temperature (Tg) and the mechanical properties of poly(MMA/BA/UMA) decreased with the increasing chain length of urethane methacrylate monomers due to the increasing flexibility of side chains. Without the effect of Tg, lower MFFT and improved mechanical properties were observed from urethane functional latexes. The improved mechanical properties were due to the increasing particle interaction by forming hydrogen bonding. Furthermore, the effect of urethane functionality in terms of the polymer composition, the location and the concentration was investigated by the batch, single-stage and two-stage semibatch polymerization of 2-[(butylcarbamoyl)oxy]ethyl methacrylate (BEM) with MMA and BA. The core-shell and homogeneous structures were evaluated by TEM, differential scanning calorimetry (DSC), and solid state nuclear magnetic resonance (SS-NMR). The compositional drift was observed from the batch

  17. Biological performances of poly(ether)urethane silver nanocomposites

    NASA Astrophysics Data System (ADS)

    Hung, Huey-Shan; Hsu, Shan-hui

    2007-11-01

    A series of nanocomposites (PU-Ag) from a polyether-type waterborne polyurethane (PU) incorporated with various amounts (15.1-113 ppm) of silver nanoparticles (approximately 5 nm) were prepared in this study. The surface morphology, biocompatibility, bacterial adhesion and free radical scavenging ability of the nanocomposites were investigated. PU-Ag nanocomposites had a different surface morphology from PU, especially at 30.2 ppm of silver. The latter nanocomposite showed enhanced cellular proliferation and reduced monocyte activation, compared with the original PU or nanocomposites with other Ag content. The nanocomposite also exhibited very low bacterial adhesion. The data obtained from a Ag+-resistant bacterial strain suggested that the release of Ag+ from the nanocomposites may not be the major cause for lower bacterial adhesion on these nanocomposites. Instead, surface morphology accounted for the general improvement of all performances.

  18. Synthesis of polycarbonate urethane elastomers and effects of the chemical structures on their thermal, mechanical and biocompatibility properties.

    PubMed

    Zhu, Rong; Wang, Yiyu; Zhang, Zongrui; Ma, Daiwei; Wang, Xinyu

    2016-06-01

    In this study, to obtain biomedical polyurethane elastomers with good mechanical properties and biocompatibility, a series of polycarbonate urethanes were synthesized via a two-step solution of polymerization method using the poly(1,6-hexanediol)carbonate diols (PCDL) as the soft segment, 4,4'-methylenebis(cyclohexyl isocyanate) (H12MDI), 1,6-hexamethylene diisocyanate (HDI) and 1,4-butanediol (BDO) as the hard segment with dibutyltin dilaurate as the catalyst. In this article, we illustrated the physical behaviors were obviously influenced by synthetic routes. And their chemical and physical structures were investigated by gel permeation chromatograph (GPC), differential scanning calorimeter (DSC), fourier transform infrared spectrography (FT-IR) and mechanical properties tests. The surface wettability were studied by contact angle measurement (CA). As a kind of short-term implant biomaterial, the results of the hemolysis and platelet adhesive tests were recorded by spectrophotometer and scanning electron microscopy (SEM), indicating the materials have a great potential for developments and applications in biomedical field. PMID:27441296

  19. Biodegradable Poly(ester urethane)urea Elastomers with Variable Amino Content for Subsequent Functionalization with Phosphorylcholine

    PubMed Central

    Fang, Jun; Ye, Sang-Ho; Shankarraman, Venkat; Huang, Yixian; Mo, Xiumei; Wagner, William R.

    2015-01-01

    While surface modification is well suited for imparting biomaterials with specific functionality for favorable cell interactions, the modification of degradable polymers would be expected to provide only temporary benefit. Bulk modification by incorporating pendant reactive groups for subsequent functionalization of biodegradable polymers would provide a more enduring approach. Towards this end, a series of biodegradable poly(ester urethane)urea elastomers with variable amino content (PEUU-NH2 polymers) were developed. Carboxylated phosphorycholine was synthesized and conjugated to the PEUU-NH2 polymers for subsequent bulk functionalization to generate PEUU-PC polymers. Synthesis was verified by 1H NMR, X-ray photoelectron spectroscopy and ATR-FTIR. The impact of amine incorporation and phosphorylcholine conjugation was shown on mechanical, thermal and degradation properties. Water absorption increased with increasing amine content, and further with PC conjugation. In wet conditions, tensile strength and initial modulus generally decreased with increasing hydrophilicity, but remained in the range of 5–30 MPa and 10–20 MPa respectively. PC conjugation was associated with significantly reduced platelet adhesion in blood contact testing and the inhibition of rat vascular smooth muscle cell proliferation. These biodegradable PEUU-PC elastomers offer attractive properties for applications as non-thrombogenic, biodegradable coatings and for blood-contacting scaffold applications. Further, the PEUU-NH2 base polymers offer the potential to have multiple types of biofunctional groups conjugated onto the backbone to address a variety of design objectives. PMID:25132273

  20. Polyimide adhesives

    NASA Technical Reports Server (NTRS)

    Progar, D. J.; Bell, V. L.; Saintclair, T. L. (Inventor)

    1974-01-01

    A process of preparing aromatic polyamide-acids for use as adhesives is described. An equimolar quantity of an aromatic dianhydride is added to a stirred solution of an aromatic diamine in a water or alcohol-miscible ether solvent to obtain a viscous polymer solution. The polymeric-acid intermediate polymer does not become insoluble but directly forms a smooth viscous polymer solution. These polyamic-acid polymers are converted, by heating in the range of 200-300 C and with pressure, to form polyimides with excellent adhesive properties.

  1. Urethane anesthesia depresses activities of thalamocortical neurons and alters its response to nociception in terms of dual firing modes

    PubMed Central

    Huh, Yeowool; Cho, Jeiwon

    2013-01-01

    Anesthetics are often used to characterize the activity of single neurons in vivo for their advantages such as reduction of noise level and convenience in noxious stimulations. Urethane has been a widely used anesthetic in thalamic studies under the assumption that sensory signals are still relayed to the thalamus under urethane anesthesia and that thalamic response would therefore reflect the response of the awake state. We tested this assumption by comparing thalamic activity in terms of tonic and burst firing modes during “the awake state” or under “urethane anesthesia” using the extracellular single unit recording technique. We first tested how thalamic relay neurons respond to the introduction of urethane, and then tested how urethane influences thalamic discharges under formalin-induced nociception. Urethane significantly depressed overall firing rates of thalamic relay neurons, which was sustained despite the delayed increase of burst activity over a 4 h recording period. Thalamic response to nociception under anesthesia was also similar overall except for the slight and transient increase of burst activity. Overall, results demonstrated that urethane suppresses the activity of thalamic relay neurons and that, despite the slight fluctuation of burst firing, formalin-induced nociception cannot significantly change the firing pattern of thalamic relay neurons that was caused by urethane. PMID:24133420

  2. In vivo cystometrogram studies in urethane-anesthetized and conscious guinea pigs.

    PubMed

    Peterson, J S; Hanson, R C; Noronha-Blob, L

    1989-05-01

    Urinary bladder cystometry using urethral catheters is described in vivo in a urethane-anesthetized guinea pig preparation and compared to an awake-animal preparation in which surgically implanted catheters were used. Anticholinergic drugs dose-dependently inhibited the peak intravesical pressure (PvesP) to a maximum of approximately 80% but had no effect on other cystometrogram (CMG) parameters (threshold pressure, bladder capacity). Stereoselectivity was evident; dexetimide but not levetimide potently depressed PvesP. Oxybutynin was equipotent (ID50 approximately 0.15 mg/kg) in both preparations and showed a similar duration of action (t1/2 = 48-53 min). The data suggests that CMG parameters and the effects of oxybutynin were not affected by urethane anesthesia, making the in vivo urethane-anesthetized guinea pig preparation a valuable tool to evaluate both the filling and voiding phases of cystometry. PMID:2724992

  3. Allergic contact dermatitis due to urethane acrylate in ultraviolet cured inks.

    PubMed Central

    Nethercott, J R; Jakubovic, H R; Pilger, C; Smith, J W

    1983-01-01

    Seven workers exposed to ultraviolet printing inks developed contact dermatitis. Six cases were allergic and one irritant. A urethane acrylate resin accounted for five cases of sensitisation, one of which was also sensitive to pentaerythritol triacrylate and another also to an epoxy acrylate resin. One instance of allergy to trimethylpropane triacrylate accounted for the sixth case of contact dermatitis in this group of workers. An irritant reaction is presumed to account for the dermatitis in the individual not proved to have cutaneous allergy by patch tests. In this instance trimethylpropane triacrylate was thought to be the most likely irritating agent. Laboratory investigation proved urethane acrylate to be an allergen. The results of investigations of the sensitisation potentials of urethane acrylate, methylmethacrylate, epoxy acrylate resins, toluene-2,4-diisocyanate, and other multifunctional acrylic monomers in the albino guinea pig are presented. The interpretation of such predictive tests is discussed. Images PMID:6223656

  4. Comparison of surface modifications of poly(ether urethanes) by chemical infusion and graft polymerization

    SciTech Connect

    Wrobleski, D.A.; Cash, D.L.; Hermes, R.E.

    1988-01-01

    Our approach to surface modification uses the chemical infusion process to introduce materials into the outermost layer of the polymeric material, thereby altering the surface without changing the bulk properties of the polymer. The infused materials may slowly diffuse out of the infusion layer if they are volatile or highly mobile. However, if polymeric infusant materials are employed, they may become chain entangled with the host polymer and result in a permanently modified surface. A second approach utilizes photo-initiated graft polymerization of poly(ether urethanes) with an appropriate monomer. We have explored both of these methods by examining the infusion of polyvinylpyrrolidone (PVP) and poly(ethylene glycol) (PEG) into commercially available poly(ether urethanes) and the graft polymerization of N-vinyl pyrrolidone onto poly(ether urethanes). Results are presented here. 7 refs., 1 tab.

  5. Biodegradable poly(ether ester urethane)urea elastomers based on poly(ether ester) triblock copolymers and putrescine: synthesis, characterization and cytocompatibility.

    PubMed

    Guan, Jianjun; Sacks, Michael S; Beckman, Eric J; Wagner, William R

    2004-01-01

    Polymers with elastomeric mechanical properties, tunable biodegradation properties and cytocompatibility would be desirable for numerous biomedical applications. Toward this end a series of biodegradable poly(ether ester urethane)urea elastomers (PEEUUs) based on poly(ether ester) triblock copolymers were synthesized and characterized. Poly(ether ester) triblock copolymers were synthesized by ring-opening polymerization of epsilon-caprolactone with polyethylene glycol (PEG). PEEUUs were synthesized from these triblock copolymers and butyl diisocyanate, with putrescine as a chain extender. PEEUUs exhibited low glass transition temperatures and possessed tensile strengths ranging from 8 to 20MPa and breaking strains from 325% to 560%. Increasing PEG length or decreasing poly(caprolactone) length in the triblock segment increased PEEUU water absorption and biodegradation rate. Human umbilical vein endothelial cells cultured in a medium supplemented with PEEUU biodegradation solution suggested a lack of degradation product cytotoxicity. Endothelial cell adhesion to PEEUUs was less than 60% of tissue culture polystyrene and was inversely related to PEEUU hydrophilicity. Surface modification of PEEUUs with ammonia gas radio-frequency glow discharge and subsequent immobilization of the cell adhesion peptide Arg-Gly-Asp-Ser increased endothelial adhesion to a level equivalent to tissue culture polystyrene. These biodegradable PEEUUs thus possessed properties that would be amenable to applications where high strength and flexibility would be desirable and exhibited the potential for tuning with appropriate triblock segment selection and surface modification. PMID:14580912

  6. Investigation of ionic conductivity of polymeric electrolytes based on poly (ether urethane) networks using positron probe

    NASA Astrophysics Data System (ADS)

    Peng, Z. L.; Wang, B.; Li, S. Q.; Wang, S. J.; Liu, H.; Xie, H. Q.

    1994-10-01

    Positron-lifetime measurements have been made for poly (ether urethane) undoped and doped with [LiClO 4]/[Unit]=0.05 in the temperature range of 120-340 K. The measured lifetime spectra were resolved into three components. The lifetime and the intensity of orthopositronium were used to evaluate the amount of the free volume in poly (ether urethane). It was found that the variation of ionic conductivity with temperature and salt concentration can be rationalised in terms of free volume consideration.

  7. Designing superhydrophobic surfaces using fluorosilsesquioxane-urethane hybrid and porous silicon gradients

    NASA Astrophysics Data System (ADS)

    Kannan, Aravindaraj G.; McInnes, Steven J. P.; Choudhury, Namita R.; Dutta, Naba K.; Voelcker, Nicolas H.

    2008-12-01

    Here we describe a new class of near superhydrophobic surfaces formed using fluorinated polyhedral oligosilsesquioxane (FluoroPOSS) urethane hybrids and porous silicon gradients (pSi). We demonstrate that the surface segregation behavior of the hydrophobic fluoro component can be controlled by the type and nature of chain extender of the urethane and resultant hydrophobic association via intra or intermolecular aggregation. The surface film formed exhibits near superhydrophobicity. This work has significant potential for applications in antifouling and self-cleaning coatings, biomedical devices, microfluidic systems and tribological surfaces.

  8. Study of the polycarbonate-urethane/metal contact in different positions during gait cycle.

    PubMed

    Gabarre, Sergio; Herrera, Antonio; Mateo, Jesús; Ibarz, Elena; Lobo-Escolar, Antonio; Gracia, Luis

    2014-01-01

    Nowadays, a growing number of young and more active patients receive hip replacement. More strenuous activities in such patients involve higher friction and wear rates, with friction on the bearing surface being crucial to ensure arthroplasty survival in the long term. Over the last years, the polycarbonate-urethane has offered a feasible alternative to conventional bearings. A finite element model of a healthy hip joint was developed and adjusted to three gait phases (heel strike, mid-stance, and toe-off), serving as a benchmark for the assessment of the results of joint replacement model. Three equivalent models were made with the polycarbonate-urethane Tribofit system implanted, one for each of the three gait phases, after reproducing a virtual surgery over the respective healthy models. Standard body-weight loads were considered: 230% body-weight toe-off, 275% body-weight mid-stance, and 350% body-weight heel strike. Contact pressures were obtained for the different models. When comparing the results corresponding to the healthy model to polycarbonate-urethane joint, contact areas are similar and so contact pressures are within a narrower value range. In conclusion, polycarbonate-urethane characteristics are similar to those of the joint cartilage. So, it is a favorable alternative to traditional bearing surfaces in total hip arthroplasty, especially in young patients. PMID:25247180

  9. QUANTITATIVE ULTRAVIOLET SPECTROSCOPY IN WEATHERING OF A MODEL POLYESTER-URETHANE COATING. (R828081E01)

    EPA Science Inventory

    Spectroscopy was used to quantify the effects of ultraviolet light on a model polyester–urethane coating as it degraded in an accelerated exposure chamber. An explorative calculation of the effective dosage absorbed by the coatings was made and, depending on the quantum...

  10. Influence Of Sterilization On Bulk And Surface Morphologies Of Copolyether-Urethane-Ureas

    NASA Astrophysics Data System (ADS)

    Knutson, K.; Lyman, D. J.

    1981-10-01

    The influence of sterilization on the bulk and surface morphologies of a copolyether-urethane-urea was studied. The bulk morphology was altered due to annealing by autoclaving and ethylene oxide sterilization. Radiation sterilization did not significantly alter the morphology. Surface morphology was not significantly altered by any of the sterilization procedures. Changes in chemical structure as the result of sterilization were not observed.

  11. Study of the Polycarbonate-Urethane/Metal Contact in Different Positions during Gait Cycle

    PubMed Central

    Herrera, Antonio; Mateo, Jesús; Lobo-Escolar, Antonio

    2014-01-01

    Nowadays, a growing number of young and more active patients receive hip replacement. More strenuous activities in such patients involve higher friction and wear rates, with friction on the bearing surface being crucial to ensure arthroplasty survival in the long term. Over the last years, the polycarbonate-urethane has offered a feasible alternative to conventional bearings. A finite element model of a healthy hip joint was developed and adjusted to three gait phases (heel strike, mid-stance, and toe-off), serving as a benchmark for the assessment of the results of joint replacement model. Three equivalent models were made with the polycarbonate-urethane Tribofit system implanted, one for each of the three gait phases, after reproducing a virtual surgery over the respective healthy models. Standard body-weight loads were considered: 230% body-weight toe-off, 275% body-weight mid-stance, and 350% body-weight heel strike. Contact pressures were obtained for the different models. When comparing the results corresponding to the healthy model to polycarbonate-urethane joint, contact areas are similar and so contact pressures are within a narrower value range. In conclusion, polycarbonate-urethane characteristics are similar to those of the joint cartilage. So, it is a favorable alternative to traditional bearing surfaces in total hip arthroplasty, especially in young patients. PMID:25247180

  12. Synthesis and application of novel EB curable polyester urethane acrylate modified by linseed oil fatty acid

    NASA Astrophysics Data System (ADS)

    Jun, Li; Xuecheng, Ju; Min, Yi; Jinshan, Wei; Hongfei, Ha

    1999-06-01

    A novel polyester urethane acrylate resin modified by linseed oil fatty acid (LFA) was synthesized and EB curing coating was formulated in this work. When the coating cured by EB radiation on the timber, the cured coating was possessed of good performances.

  13. Thio-urethanes Improve Properties of Dual-cured Composite Cements

    PubMed Central

    Bacchi, A.; Dobson, A.; Ferracane, J.L.; Consani, R.; Pfeifer, C.S.

    2014-01-01

    This study aims at modifying dual-cure composite cements by adding thio-urethane oligomers to improve mechanical properties, especially fracture toughness, and reduce polymerization stress. Thiol-functionalized oligomers were synthesized by combining 1,3-bis(1-isocyanato-1-methylethyl)benzene with trimethylol-tris-3-mercaptopropionate, at 1:2 isocyanate:thiol. Oligomer was added at 0, 10 or 20 wt% to BisGMA-UDMA-TEGDMA (5:3:2, with 25 wt% silanated inorganic fillers) or to one commercial composite cement (Relyx Ultimate, 3M Espe). Near-IR was used to measure methacrylate conversion after photoactivation (700 mW/cm2 × 60s) and after 72 h. Flexural strength and modulus, toughness, and fracture toughness were evaluated in three-point bending. Polymerization stress was measured with the Bioman. The microtensile bond strength of an indirect composite and a glass ceramic to dentin was also evaluated. Results were analyzed with analysis of variance and Tukey’s test (α = 0.05). For BisGMA-UDMA-TEGDMA cements, conversion values were not affected by the addition of thio-urethanes. Flexural strength/modulus increased significantly for both oligomer concentrations, with a 3-fold increase in toughness at 20 wt%. Fracture toughness increased over 2-fold for the thio-urethane modified groups. Contraction stress was reduced by 40% to 50% with the addition of thio-urethanes. The addition of thio-urethane to the commercial cement led to similar flexural strength, toughness, and conversion at 72h compared to the control. Flexural modulus decreased for the 20 wt% group, due to the dilution of the overall filler volume, which also led to decreased stress. However, fracture toughness increased by up to 50%. The microtensile bond strength increased for the experimental composite cement with 20 wt% thio-urethane bonding for both an indirect composite and a glass ceramic. Novel dual-cured composite cements containing thio-urethanes showed increased toughness, fracture toughness and

  14. Thio-urethanes improve properties of dual-cured composite cements.

    PubMed

    Bacchi, A; Dobson, A; Ferracane, J L; Consani, R; Pfeifer, C S

    2014-12-01

    This study aims at modifying dual-cure composite cements by adding thio-urethane oligomers to improve mechanical properties, especially fracture toughness, and reduce polymerization stress. Thiol-functionalized oligomers were synthesized by combining 1,3-bis(1-isocyanato-1-methylethyl)benzene with trimethylol-tris-3-mercaptopropionate, at 1:2 isocyanate:thiol. Oligomer was added at 0, 10 or 20 wt% to BisGMA-UDMA-TEGDMA (5:3:2, with 25 wt% silanated inorganic fillers) or to one commercial composite cement (Relyx Ultimate, 3M Espe). Near-IR was used to measure methacrylate conversion after photoactivation (700 mW/cm(2) × 60s) and after 72 h. Flexural strength and modulus, toughness, and fracture toughness were evaluated in three-point bending. Polymerization stress was measured with the Bioman. The microtensile bond strength of an indirect composite and a glass ceramic to dentin was also evaluated. Results were analyzed with analysis of variance and Tukey's test (α = 0.05). For BisGMA-UDMA-TEGDMA cements, conversion values were not affected by the addition of thio-urethanes. Flexural strength/modulus increased significantly for both oligomer concentrations, with a 3-fold increase in toughness at 20 wt%. Fracture toughness increased over 2-fold for the thio-urethane modified groups. Contraction stress was reduced by 40% to 50% with the addition of thio-urethanes. The addition of thio-urethane to the commercial cement led to similar flexural strength, toughness, and conversion at 72h compared to the control. Flexural modulus decreased for the 20 wt% group, due to the dilution of the overall filler volume, which also led to decreased stress. However, fracture toughness increased by up to 50%. The microtensile bond strength increased for the experimental composite cement with 20 wt% thio-urethane bonding for both an indirect composite and a glass ceramic. Novel dual-cured composite cements containing thio-urethanes showed increased toughness, fracture toughness and

  15. Adhesion of Staphylococcus epidermidis to biomaterials is inhibited by fibronectin and albumin

    PubMed Central

    Linnes, J.C.; Mikhova, K.; Bryers, J.D.

    2012-01-01

    Decades of contradictory results have obscured the exact role of adsorbed fibronectin in the adhesion of the bacterium, Staphylococcus epidermidis (S. epidermidis), to biomaterials. Here, the ability of adsorbed fibronectin (FN) or bovine serum albumin (BSA) to modulate S. epidermidis adhesion to various biomaterials is reported. FN or BSA were adsorbed in increasing surface densities up to saturated monolayer coverage onto various common biomaterials, including poly(ethylene terephthalate) (PET), fluorinated ethylene propylene (FEP), poly(ether urethane) (PEU), silicone, and borosilicate glass. Despite the wide range of surface characteristics represented, adsorption isotherms varied only subtly between materials for the two proteins considered. S. epidermidis adhesion to the various protein-coated biomaterials was quantified in a static-fluid batch adhesion assay. While slight differences in overall adherent cell numbers were observed between the various protein-coated substrata, all materials exhibited significant dose-dependent decreases in S. epidermidis adhesion with increasing adsorption of either protein (FN, BSA) to all surfaces. Results here indicate that S. epidermidis adhesion to FN-coated surfaces is not a specific adhesion (i.e., receptor:ligand) mediated process, as no significant difference in adhesion was found between FN- and BSA-coated materials. Rather, results indicate that increasing surface density of either FN or BSA actually inhibited S. epidermidis adhesion to all biomaterials examined. PMID:22566405

  16. Poly(ester urethane) guides for peripheral nerve regeneration.

    PubMed

    Chiono, Valeria; Sartori, Susanna; Rechichi, Alfonsina; Tonda-Turo, Chiara; Vozzi, Giovanni; Vozzi, Federico; D'Acunto, Mario; Salvadori, Claudia; Dini, Francesca; Barsotti, Giovanni; Carlucci, Fabio; Burchielli, Silvia; Nicolino, Silvia; Audisio, Chiara; Perroteau, Isabelle; Giusti, Paolo; Ciardelli, Gianluca

    2011-02-11

    A biocompatible and elastomeric PU was synthesized from low-molecular-weight PCL as macrodiol, CMD as chain extender and HDI as chain linker for applications in the field of peripheral nerve repair. PU cast films supported in vitro attachment and proliferation of NOBEC. The in vitro adhesion and proliferation of S5Y5 neuroblastoma cells on the inner surface of uncoated, gelatin- and PL-coated PU guides were compared. Due to their superior in vitro performance, PL-coated PU guides were tested in vivo for the repair of 1.8 cm-long defects in rat sciatic nerves. The progressive regeneration was confirmed by EMG and histological analysis showing the presence of regenerating fibers in the distal stumps. PMID:21104881

  17. A water blown urethane insulation for use in cryogenic environments

    NASA Technical Reports Server (NTRS)

    Blevins, Elana; Sharpe, Jon

    1995-01-01

    Thermal Protection Systems (TPS) of NASA's Space Shuttle External Tank include polyurethane and polyisocyanurate modified polyurethane foam insulations. These insulations, currently foamed with CFC 11 blowing agent, serve to maintain cryogenic propellant quality, maintain the external tank structural temperature limits, and minimize the formation of ice and frost that could potentially damage the ceramic insulation on the space shuttle orbiter. During flight the external tank insulations are exposed to mechanical, thermal and acoustical stresses. TPS must pass cryogenic flexure and substrate adhesion tests at -253 C, aerothermal and radiant heating tests at fluxes up to approximately 14 kilowatts per square meter, and thermal conductivity tests at cryogenic and elevated temperatures. Due to environmental concerns, the polyurethane insulation industry and the External Tank Project are tasked with replacing CFC 11. The flight qualification of foam insulations employing HCFC 141b as a foaming agent is currently in progress; HCFC 141b blown insulations are scheduled for production implementation in 1995. Realizing that the second generation HCFC blowing agents are an interim solution, the evaluation of third generation blowing agents with zero ozone depletion potential is underway. NASA's TPS Materials Research Laboratory is evaluating third generation blowing agents in cryogenic insulations for the External Tank; one option being investigated is the use of water as a foaming agent. A dimensionally stable insulation with low friability, good adhesion to cryogenic substrates, and acceptable thermal conductivity has been developed with low viscosity materials that are easily processed in molding applications. The development criteria, statistical experimental approach, and resulting foam properties will be presented.

  18. Low doses of urethane effectively inhibit spinal seizures evoked by sudden cooling of toad isolated spinal cord

    SciTech Connect

    Pina-crespo, J.C.; Dalo, N.L. )

    1992-01-01

    The effect of low doses of urethane on three phases of spinal seizures evoked by sudden cooling (SSSC) of toad isolated spinal cord was studied. In control toads, SSSC began with a latency of 91[plus minus]3 sec exhibiting brief tremors, followed by clonic muscle contractions and finally reaching a tonic contraction. The latency of onset of seizures was significantly enhanced. The tonic phase was markedly abolished in toads pretreated intralymphaticaly with 0.15 g/kg of urethane. Tremors were the only phase observed in 55% of toads that received doses of 0.2 g/kg, and a total blockage of seizures was seen after doses of 0.25 g/kg of urethane in 50% of the preparations. A possible depressant effect of urethane on transmission mediated by excitatory amino acids is suggested.

  19. Analeptic effect of centrally administered histamine H2-receptor agonist dimaprit but not impromidine in urethane-anesthetized rats.

    PubMed

    Paakkari, I; Karppanen, H

    1982-02-01

    Intracerebroventricularly administered dimaprit decreased the depth of urethane anaesthesia. Ventilatory stimulation, positive corneal reflex and increased susceptibility to pain were observed. Furthermore, dimaprit decreased the lethal effect of large doses of urethane. The analeptic property of dimaprit was not shared by the potent H2-receptor agonist, impromidine, Histamine increased ventilatory tidal volume but no other stimulatory effects were observed. These findings suggest that the analeptic effects of dimaprit were not mediated by H2-receptors. Among the analeptic effects of dimaprit, only the protection against urethane toxicity was antagonized by metiamide. However, this phenomenon appeared to be due to the nonspecific interaction between the three bradypnoeic drugs metiamide, dimaprit and urethane. The histamine-induced increase in ventilatory tidal volume was not antagonized by diphenhydramine or metiamide, suggesting the existence of a novel histaminergic mechanism in the central nervous system. PMID:6121302

  20. Synthesis and characterization of X-ray opaque polycarbonate urethane: Effect of a dihalogenated chain extender on radiopacity and hemocompatibility.

    PubMed

    Kiran, S; Joseph, Roy

    2015-07-01

    An inherently radiopaque poly(carbonate urethane) containing fluorine and iodine atoms in the polymer chain was synthesized and characterized. Radiopaque polyurethane was synthesized from 1,6-diisocyanatohexane (HDI), poly (hexamethylene carbonate)diol (PHCD) and a newly synthesized chain extender having fluorine and iodine in the molecule, namely, 4,4'-(1,1,1,3,3,3-hexafluoropropane-2,2-diyl)bis(2,6-diiodophenol) (IBAF). IBAF monomer imparted radiopacity and improved the hemocompatibility of the resultant polymer. For comparative evaluation, polyurethanes (PU) were synthesized by reacting monomers HDI and PHCD without any chain extender and also by reacting HDI and PHCD along with noniodinated, but fluorine containing, version of the above chain extender, namely, 4,4'-(Hexafluoroisopropylidene) diphenol (BAF). Chain extended PUs showed improved mechanical and thermal properties, and hemocompatibility compared to the nonchain extended PU. Radiopacity measurements by fluoroscopy showed that IBAF incorporated PU of 200 µm thickness had radiopacity equivalent to that of 25% barium sulfate filled noniodinated PU of same thickness and to that of 0.6-mm thick aluminum wedge. In vivo imaging using a rabbit cadaver model showed clearly distinguishable image of IBAF incorporated PU sample. All the PU materials were noncytotoxic to L929 mouse fibroblast cells. Preliminary results obtained from blood-material interaction studies showed that incorporation of fluorinated chain extenders in the PUs resulted in significant reduction in the adhesion of white blood cells onto the PU material surface and also resulted in prolonged partial thromboplastin time. Results suggest that incorporation of fluorine and iodine containing chain extenders would lead to the development PU with improved hemocompatibility and radiopacity. PMID:25345782

  1. Cast iron (CI) based soft magnetic BMG Ci88.3Al2Ga1P4.35B4.35

    NASA Astrophysics Data System (ADS)

    Kane, S. N.; Lee, H. J.; Jeong, Y. H.; Varga, L. K.

    2009-01-01

    Thermal stability, structure, and magnetic properties of bulk type Ci88.3Al2Ga1P4.35B4.35 alloy in ribbon form have been studied using differential thermal analysis, x-ray diffraction and magnetic measurements. Results reveal that crystallization peak temperature (Tx) and Curie temperature (Tc) of the as-cast alloy are respectively 513 and 370 °C. Crystallization of the specimen starts after annealing at 460 °C and α-Fe is precipitated out. Annealing at temperatures higher than 515 °C, produces apart from α-Fe, hard magnetic precipitants (Fe2B, Fe3B), which deteriorate the soft magnetic properties. Lowest coercive field - 9.8 A/m, highest saturation of induction - 1.55 Tesla and best losses - 0.42 W/kg (at 50 Hz and 0.4 kA/m) were obtained for as-cast specimen. Observed good soft magnetic properties of these low cost cast-iron based alloys suggest perspective applications of these soft magnetic alloys as an alternative to the conventional Fe-Si electrical steel and Mn-Zn ferrites.

  2. Caryocar brasiliense camb protects against genomic and oxidative damage in urethane-induced lung carcinogenesis

    PubMed Central

    Colombo, N.B.R.; Rangel, M.P.; Martins, V.; Hage, M.; Gelain, D.P.; Barbeiro, D.F.; Grisolia, C.K.; Parra, E.R.; Capelozzi, V.L.

    2015-01-01

    The antioxidant effects of Caryocar brasiliense Camb, commonly known as the pequi fruit, have not been evaluated to determine their protective effects against oxidative damage in lung carcinogenesis. In the present study, we evaluated the role of pequi fruit against urethane-induced DNA damage and oxidative stress in forty 8-12 week old male BALB/C mice. An in vivo comet assay was performed to assess DNA damage in lung tissues and changes in lipid peroxidation and redox cycle antioxidants were monitored for oxidative stress. Prior supplementation with pequi oil or its extract (15 µL, 60 days) significantly reduced urethane-induced oxidative stress. A protective effect against DNA damage was associated with the modulation of lipid peroxidation and low protein and gene expression of nitric oxide synthase. These findings suggest that the intake of pequi fruit might protect against in vivo genotoxicity and oxidative stress. PMID:26200231

  3. Degradation kinetics of poly(ether-urethane) Estane® induced by electron irradiation

    NASA Astrophysics Data System (ADS)

    Dannoux, A.; Esnouf, S.; Begue, J.; Amekraz, B.; Moulin, C.

    2005-07-01

    Radiation effects on a segmented aromatic poly(ether-urethane) induced by electron beam irradiation under oxygen atmosphere were investigated using Fourier transform infrared spectroscopy (FTIR) and electron paramagnetic resonance (EPR) in order to determine the degradation mechanisms. Thin films have been irradiated under a dose rate of 1 MGy/h with absorbed doses varying from 25 to 1000 kGy under O2. FTIR spectra have shown the formation of hydroperoxides, carboxylic acids, primary amines, alcohols, esters and formates. Moreover, the decrease of urethane and ether absorbances revealed the degradation of both soft and hard segments. Spin-trapping technique was used to monitor the evolution of short-lived peroxy and alkyl radicals at room temperature. Finally, a mechanism of degradation for electron irradiated polyurethane is proposed.

  4. Preparation and properties of an internal mold release for rigid urethane foam

    NASA Astrophysics Data System (ADS)

    Paker, B. G.

    1980-08-01

    Most mold release agents used in the molding of rigid polyurethane foam are applied to the internal surfaces of the mold. These materials form a thin layer between the surface of the mold and the foam, allowing for easy release of the molded parts. This type of mold release must be applied prior to each molding operation; and, after repeated use, cleaning of the mold is required. Small amounts of this mold release are transferred to the molded part, resulting in a part with poor surface bondability characteristics. An internal release agent, which can be mixed in a urethane foam resin was investigated. The internal mold release provided good releasability and resulted in urethane foam that has excellent surface bondability. No compatibility problems are expected from the use of this type of release agent.

  5. New cationic biodegradable poly(urethane-co-ester): synthesis, structural characterization, modification and gene delivery.

    PubMed

    Chang, Wei-Yang; Hsiao, Yu-Che; Shau, Min-Da

    2012-01-01

    To improve the transfection efficiency of poly(urethane-co-ester) and the cytotoxicity of PEI25k with DNA, we synthesized a new poly(urethane-co-ester), PUE, bearing ester linkages and amino groups in the backbone and urethane linkages in the side-chain, and then prepared a binary mixture, PUE-PEI25k, using a physical blending method. The structure of PUE was confirmed by FT-IR and NMR spectra. Both poly(urethane-co-ester), PUE, and binary mixture PUE-PEI25k, readily self-assembled with plasmid DNA (pCMV-βgal) in a HEPES buffer, were characterized by dynamic light scattering. The results revealed that PUE and PUE-PEI25k were able to self-assemble plasmid DNA into PUE/DNA and PUE-PEI25k/DNA nano-complexes small enough to enter a cell through endocytosis. Titration studies were performed to determine the buffering capacities of PUE and PUE-PEI25k. The COS-7 cell viability in the presence of PEI25k, PUE and PUE-PEI25k was studied. At low mass ratio of PUE/PEI25k (150:1), it was found that the PUE-PEI25k/DNA complexes were able to transfect COS-7 cells in vitro with a high efficiency comparable to a well-known gene carrier, PEI25k/DNA. The results indicate that the binary mixture PUE-PEI25k is an attractive cationic carrier for gene delivery and an interesting candidate for further study. PMID:21156103

  6. Thio-urethane oligomers improve the properties of light-cured resin cements

    PubMed Central

    Bacchi, Ataís; Consani, Rafael L.; Martim, Gedalias C.; Pfeifer, Carmem S.

    2015-01-01

    Thio-urethanes were synthesized by combining 1,6-Hexanediol-diissocyante (aliphatic) with pentaerythritol tetra-3-mercaptopropionate (PETMP) or 1,3-bis(1-isocyanato-1-methylethyl)benzene (aromatic) with trimethylol-tris-3-mercaptopropionate (TMP), at 1:2 isocyanate:thiol, leaving pendant thiols. Oligomers were added at 10–30 phr to BisGMA-UDMA-TEGDMA (5:3:2, BUT). 25wt% silanated inorganic fillers were added. Commercial cement (Relyx Veneer, 3M-ESPE) was also evaluated with 10–20 phr of aromatic oligomer. Near-IR was used to follow methacrylate conversion (DC) and rate of polymerization (Rpmax). Mechanical properties were evaluated in three-point bending (ISO 4049) for flexural strength/modulus (FS/FM, and toughness), and notched specimens (ASTM Standard E399-90) for fracture toughness (KIC). Polymerization stress (PS) was measured on the Bioman. Volumetric shrinkage (VS, %) was measured with the bonded disk technique. Results were analyzed with ANOVA/Tukey’s test (α=5%). In general terms, for BUT cements, conversion and mechanical properties in flexure increased for selected groups with the addition of thio-urethane oligomers. The aromatic versions resulted in greater FS/FM than aliphatic. Fracture toughness increased by twofold in the experimental groups (from 1.17±0.36 to around 3.23±0.22 MPa.m1/2). Rpmax decreased with the addition of thio-urethanes, though the vitrification point was not statistically different from the control. VS and PS decreased with both oligomers. For the commercial cement, 20 phr of oligomer increased DC, vitrification, reduced Rpmax and also significantly increased KIC, and reduced PS and FM. Thio-urethane oligomers were shown to favorably modify conventional dimethacrylate networks. Significant reductions in polymerization stress were achieved at the same time conversion and fracture toughness increased. PMID:25740124

  7. High Performance Laminates Using Blended Urethane Resin Chemistry

    SciTech Connect

    Simmons, Kevin L.; Jones, George G.; Walsh, Sean P.; Wood, Geoff M.

    2005-03-24

    Hybrid blended resin systems have the potential to provide excellent impact performance in structured laminates. Although mostly under development for sheet molding compound (SMC) applications using glass fiber with high levels of fillers, the resins have been found to be useful in liquid molding applications with other high-performance fiber systems. A research pro-gram to develop the molding capability, property data, and capability to model the composites using newly de-veloped codes and modeling techniques was initiated through the Department of Energy’s Office of Freedom-Car and Vehicle Technologies. Results have shown ex-cellent adhesion to different fiber systems as evidenced by mechanical properties, and a capability to develop very good impact results – thereby allowing thin panel structures to be developed. Comparison to predicted me-chanical properties has been achieved and mechanisms for the development of observed high energy absorption under impact loadings are being investigated. Scale ef-fects based on panel thickness, fiber type loading, and position in laminate are being investigated. DOE pro-gram sponsorship was provided by Dr. Sidney Diamond, Technical Area Development Manager for High-Strength Weight-Reduction Materials.

  8. Spectroscopic, semiempirical studies and antibacterial activity of new urethane derivatives of natural polyether antibiotic - Monensin A

    NASA Astrophysics Data System (ADS)

    Huczyński, Adam; Stefańska, Joanna; Piśmienny, Mieszko; Brzezinski, Bogumil

    2013-02-01

    A series of new Monensin A dimers linked by diurethane moiety were synthesised and their molecular structures were studied using ESI-MS, FT-IR, 1H and 13C NMR and PM5 methods. The results showed that the compounds form a pseudo-cyclic structure stabilized by three intramolecular hydrogen bonds and the sodium cation was coordinated by five oxygen atoms of polyether skeleton of Monensin moiety. The NMR and FT-IR data of complexes of Monensin urethane sodium salts demonstrated that within the pseudo-cyclic structure the carbonyl oxygen atom of the urethane group did not coordinate the sodium cation. Monensin urethanes were tested in vitro for the activity against Gram-positive and Gram-negative bacteria and fungi as well as against a series of clinical isolates of Staphylococcus: methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-sensitive S. aureus (MSSA). The most active compound against MRSA and MSSA was 1,4-phenylene diurethane of Monensin with MIC 10.4-41.4 μmol/L).

  9. Spectroscopic study on water diffusion in poly(ester urethane) block copolymer matrix.

    PubMed

    Wang, Wei; Jin, Ying; Su, Zhaohui

    2009-12-01

    The diffusion of water in a phase-separated biodegradable poly(ester urethane) shape-memory polymer with poly(epsilon-caprolactone) (PCL) as the soft segment was investigated using time-resolved FTIR-ATR. On the basis of the band fitting and water ordering in drawn films, the broad water band in the 3800-2800 cm(-1) region was decomposed into four bands located at 3620, 3510, 3400, and 3260 cm(-1), and the first two components at 3620 and 3510 cm(-1) were assigned to the vibrations of antisymmetric and symmetric stretching of water hydrogen bonded with the C=O group of the soft segment. The other two were associated with water bonded to the urethane hard segments in the forms of N-H:O-H:O=C bridge hydrogen bond and double hydrogen bonds with two C=O groups, respectively. Furthermore, band fitting and two-dimensional correlation analyses revealed that in the diffusion process, water first diffuses into the continuous soft-rich PCL phase and then into the hard-rich urethane domains, forming double hydrogen bonds with two C=O groups prior to the bridge hydrogen bond in the form of N-H:O-H:O=C. PMID:19894687

  10. Thiol-containing degradable poly(thiourethane-urethane)s for tissue engineering.

    PubMed

    Eglin, David; Griffon, Stéphane; Alini, Mauro

    2010-01-01

    Poly(thiourethane-urethane)s with varying amounts of sulphur were synthesised by a two-step polycondensation consisting of the sequential addition of 1,6-hexamethylene diisocyanate and bis(2-mercaptoethyl) ether in a poly(epsilon-caprolactone) diol solution. Polymers prepared had high weight-average molecular weight and typical microdomains separation, as shown by size-exclusion chromatography and thermal analysis. Polymer surfaces were characterized by X-ray photoelectron spectroscopy and atomic force microscopy. The quantification of thiol groups at the surface was assessed using a fluorescent assay. Thiol concentration ranged between 7 and 14 nmol/cm, and was directly related to the amount of sulphur introduced in the polymerization and the macromolecule chains orientation at the surfaces. A preliminary in vitro degradation study and a proliferation assay were performed. The poly(thiourethane-urethane)s may have important applications as biodegradable and biocompatible materials for cartilage and bone tissue engineering. The surface thiol groups add the prospect of further functionalization. This is an important benefit compared to biodegradable poly(urethane)s that usually present low biological activity. PMID:20233504

  11. Urban, traffic- related particles and lung tumors in urethane treated mice

    PubMed Central

    Pereira, Fernanda Alves Cangerana; Lemos, Miriam; Mauad, Thaís; de Assunção, João Vicente; Saldiva, Paulo Hilário Nascimento

    2011-01-01

    OBJECTIVE: The present study was designed to evaluate the effects of urban, traffic-related, fine particulate matter (PM2.5) on mice lung tumorigenesis under controlled exposure conditions. METHODS: Four groups of female Swiss mice were treated with intraperitonial injections of urethane and saline solution. Urethane was used to start the carcinogenesis process. The animals were housed in two chambers receiving filtered and polluted air. In the polluted air chamber, pollutant levels were low. After two months of exposure, the animals were euthanized and lung tumoral nodules were counted. RESULTS: Saline-treated animals showed no nodules. Urethane-treated animals showed 2.0+2.0 and 4.0+3.0 nodules respectively, in the filtered and non-filtered chambers (p = 0.02), thus showing experimental evidence of increased carcinogenic-induced lung cancer with increasing PM2.5 exposure. CONCLUSION: Our data support the concept that low levels of PM2.5 may increase the risk of developing lung tumors. PMID:21808874

  12. Thermal Characterization of Adhesive

    NASA Technical Reports Server (NTRS)

    Spomer, Ken A.

    1999-01-01

    The current Space Shuttle Reusable Solid Rocket Motor (RSRM) nozzle adhesive bond system is being replaced due to obsolescence. Down-selection and performance testing of the structural adhesives resulted in the selection of two candidate replacement adhesives, Resin Technology Group's Tiga 321 and 3M's EC2615XLW. This paper describes rocket motor testing of these two adhesives. Four forty-pound charge motors were fabricated in configurations that would allow side by side comparison testing of the candidate replacement adhesives and the current RSRM adhesives. The motors provided an environment where the thermal performance of adhesives in flame surface bondlines was compared. Results of the FPC testing show that: 1) The phenolic char depths on radial bond lines is approximately the same and vary depending on the position in the blast tube regardless of which adhesive was used; 2) The adhesive char depth of the candidate replacement adhesives is less than the char depth of the current adhesives; 3) The heat-affected depth of the candidate replacement adhesives is less than the heat-affected depth of the current adhesives; and 4) The ablation rates for both replacement adhesives are slower than that of the current adhesives.

  13. [Effects of ketamine and urethane on stimulation-induced c-fos expression in neurons of cat visual cortex].

    PubMed

    Wang, Ke; Zhu, Hui; Chen, Cui-Yun; Li, Peng; Jin, Cai-Hong; Wang, Zi-Lu; Jiang, San; Hua, Tian-Miao

    2013-12-01

    The effects of ketamine and urethane on neuronal activities remain in debate. As a member of immediate early genes family, the expression of c-fos is stimulation dependent and could be treated as an index to evaluate the strength of neural activities. In this study, SABC immunohistochemical techniques were applied to compare the c-fos expression in neurons of the primary visual cortex (V1) of cats and therefore, to evaluate the effects of acute anesthesia with ketamine HCl and uethane on inhibiting neural activities. Our results showed that compared with control cats, there were no significant differences with the average densities of Nissl-stained V1 neurons in each cortical layers of either urethane or ketamine anesthetized cats. In urethane anesthetized cats, neither the average densities nor the immunoreactive intensities of c-fos positive V1 neurons showed significant difference with that of control ones. However, both the average densities and immunoreactive intensities of c-fos positive V1 neurons in ketamine anesthetized cats decreased significantly compared with that of control and urethane anesthetized cats. These results suggested that ketamine has strong inhibitory effects on the activities of visual cortical neurons, whereas urethane did not. PMID:24415690

  14. Understanding Marine Mussel Adhesion

    SciTech Connect

    H. G. Silverman; F. F. Roberto

    2007-12-01

    In addition to identifying the proteins that have a role in underwater adhesion by marine mussels, research efforts have focused on identifying the genes responsible for the adhesive proteins, environmental factors that may influence protein production, and strategies for producing natural adhesives similar to the native mussel adhesive proteins. The production-scale availability of recombinant mussel adhesive proteins will enable researchers to formulate adhesives that are waterimpervious and ecologically safe and can bind materials ranging from glass, plastics, metals, and wood to materials, such as bone or teeth, biological organisms, and other chemicals or molecules. Unfortunately, as of yet scientists have been unable to duplicate the processes that marine mussels use to create adhesive structures. This study provides a background on adhesive proteins identified in the blue mussel, Mytilus edulis, and introduces our research interests and discusses the future for continued research related to mussel adhesion.

  15. Understanding Marine Mussel Adhesion

    PubMed Central

    Roberto, Francisco F.

    2007-01-01

    In addition to identifying the proteins that have a role in underwater adhesion by marine mussels, research efforts have focused on identifying the genes responsible for the adhesive proteins, environmental factors that may influence protein production, and strategies for producing natural adhesives similar to the native mussel adhesive proteins. The production-scale availability of recombinant mussel adhesive proteins will enable researchers to formulate adhesives that are water-impervious and ecologically safe and can bind materials ranging from glass, plastics, metals, and wood to materials, such as bone or teeth, biological organisms, and other chemicals or molecules. Unfortunately, as of yet scientists have been unable to duplicate the processes that marine mussels use to create adhesive structures. This study provides a background on adhesive proteins identified in the blue mussel, Mytilus edulis, and introduces our research interests and discusses the future for continued research related to mussel adhesion. PMID:17990038

  16. Understanding marine mussel adhesion.

    PubMed

    Silverman, Heather G; Roberto, Francisco F

    2007-01-01

    In addition to identifying the proteins that have a role in underwater adhesion by marine mussels, research efforts have focused on identifying the genes responsible for the adhesive proteins, environmental factors that may influence protein production, and strategies for producing natural adhesives similar to the native mussel adhesive proteins. The production-scale availability of recombinant mussel adhesive proteins will enable researchers to formulate adhesives that are water-impervious and ecologically safe and can bind materials ranging from glass, plastics, metals, and wood to materials, such as bone or teeth, biological organisms, and other chemicals or molecules. Unfortunately, as of yet scientists have been unable to duplicate the processes that marine mussels use to create adhesive structures. This study provides a background on adhesive proteins identified in the blue mussel, Mytilus edulis, and introduces our research interests and discusses the future for continued research related to mussel adhesion. PMID:17990038

  17. Electrospun Poly(ester-Urethane)- and Poly(ester-Urethane-Urea) Fleeces as Promising Tissue Engineering Scaffolds for Adipose-Derived Stem Cells

    PubMed Central

    Gugerell, Alfred; Kober, Johanna; Laube, Thorsten; Walter, Torsten; Nürnberger, Sylvia; Grönniger, Elke; Brönneke, Simone; Wyrwa, Ralf; Schnabelrauch, Matthias; Keck, Maike

    2014-01-01

    An irreversible loss of subcutaneous adipose tissue in patients after tumor removal or deep dermal burns makes soft tissue engineering one of the most important challenges in biomedical research. The ideal scaffold for adipose tissue engineering has yet not been identified though biodegradable polymers gained an increasing interest during the last years. In the present study we synthesized two novel biodegradable polymers, poly(ε-caprolactone-co-urethane-co-urea) (PEUU) and poly[(L-lactide-co-ε-caprolactone)-co-(L-lysine ethyl ester diisocyanate)-block-oligo(ethylene glycol)-urethane] (PEU), containing different types of hydrolytically cleavable bondings. Solutions of the polymers at appropriate concentrations were used to fabricate fleeces by electrospinning. Ultrastructure, tensile properties, and degradation of the produced fleeces were evaluated. Adipose-derived stem cells (ASCs) were seeded on fleeces and morphology, viability, proliferation and differentiation were assessed. The biomaterials show fine micro- and nanostructures composed of fibers with diameters of about 0.5 to 1.3 µm. PEUU fleeces were more elastic, which might be favourable in soft tissue engineering, and degraded significantly slower compared to PEU. ASCs were able to adhere, proliferate and differentiate on both scaffolds. Morphology of the cells was slightly better on PEUU than on PEU showing a more physiological appearance. ASCs differentiated into the adipogenic lineage. Gene analysis of differentiated ASCs showed typical expression of adipogenetic markers such as PPARgamma and FABP4. Based on these results, PEUU and PEU meshes show a promising potential as scaffold materials in adipose tissue engineering. PMID:24594923

  18. Preliminary In Vitro Assessment of Stem Cell Compatibility with Cross-Linked Poly(ε-caprolactone urethane) Scaffolds Designed through High Internal Phase Emulsions

    PubMed Central

    Changotade, Sylvie; Radu Bostan, Gabriela; Consalus, Anne; Poirier, Florence; Peltzer, Juliette; Lataillade, Jean-Jacques; Lutomski, Didier; Rohman, Géraldine

    2015-01-01

    By using a high internal phase emulsion process, elastomeric poly(ε-caprolactone urethane) (PCLU) scaffolds were designed with pores size ranging from below 150 μm to 1800 μm and a porosity of 86% making them suitable for bone tissue engineering applications. Moreover, the pores appeared to be excellently interconnected, promoting cellularization and future bone ingrowth. This study evaluated the in vitro cytotoxicity of the PCLU scaffolds towards human mesenchymal stem cells (hMSCs) through the evaluation of cell viability and metabolic activity during extract test and indirect contact test at the beginning of the scaffold lifetime. Both tests demonstrated that PCLU scaffolds did not induce any cytotoxic response. Finally, direct interaction of hMSCs and PCLU scaffolds showed that PCLU scaffolds were suitable for supporting the hMSCs adhesion and that the cells were well spread over the pore walls. We conclude that PCLU scaffolds may be a good candidate for bone tissue regeneration applications using hMSCs. PMID:26161094

  19. Self-Assembled Cationic Biodegradable Nanoparticles from pH-Responsive Amino-Acid-Based Poly(Ester Urea Urethane)s and Their Application As a Drug Delivery Vehicle.

    PubMed

    He, Mingyu; Potuck, Alicia; Kohn, Julie C; Fung, Katharina; Reinhart-King, Cynthia A; Chu, Chih-Chang

    2016-02-01

    The objective of this study is to develop a new family of biodegradable and biologically active copolymers and their subsequent self-assembled cationic nanoparticles as better delivery vehicles for anticancer drugs to achieve the synergism between the cytotoxicity effects of the loaded drugs and the macrophage inflammatory response of the delivery vehicle. This family of cationic nanoparticles was formulated from a new family of amphiphilic cationic Arginine-Leucine (Arg-Leu)-based poly(ester urea urethane) (Arg-Leu PEUU) synthesized from four building blocks (amino acids, diols, glycerol α-monoallyl ether, and 1,6 hexamethylene diisocyanate). The chemical, physical, and biological properties of Arg-Leu PEUU biomaterials can be tuned by controlling the feed ratio of the four building blocks. The Arg-Leu PEUU copolymers have weight-average molecular weights from 13.4 to 16.8 kDa and glass-transition temperatures from -3.4 to -4.6 °C. The self-assembled cationic nanoparticles (Arg-Leu PEUU NPs) were prepared using a facile dialysis method. Arg-Leu PEUU NPs have average diameters ranging from 187 to 272 nm, show good biocompatibility with 3T3 fibroblasts, and they support bovine aortic endothelial cell (BAEC) proliferation and adhesion. Arg-Leu PEUU NPs also enhanced the macrophages' production of tumor necrosis factor-α (TNF-α) and nitric oxide (NO), but produced relatively low levels of interleukin-10 (IL-10), and therefore, the antitumor activity of macrophages might be enhanced. Arg-Leu PEUU NPs were taken up by HeLa cells after 4 h of incubation. The in vitro hemolysis assay showed the cationic Arg-Leu PEUU NPs increased their chance of endosomal escape at a more acidic pH. Doxorubicin (DOX) was successfully incorporated into the Arg-Leu PEUU NPs, and the DOX-loaded Arg-Leu PEUU NPs exhibited a pH-dependent drug release profile with accelerated release kinetics in a mild acidic condition. The DOX-loaded 6-Arg-4-Leu-4 A/L-2/1 NPs showed higher HeLa cell

  20. Evaluation of the efficiency of radioactive decontamination for alkyd and epoxy-urethane coating systems

    NASA Astrophysics Data System (ADS)

    Jevremović, Milutin; Milošević, Bratislav; Lazarević, Nataša

    2010-01-01

    This article presents experimental results obtained by the investigation of the efficiency of radioactive decontamination of a metal surface with alkyd and epoxy-urethane coating systems, which are used for the painting of military equipment. During the evaluation of the efficiency of decontamination, the impact of contaminants on the coating was not examined but the amount of contaminants residual after decontamination was, and was determined by activity measurements of the surface. The samples for testing were painted aluminum plates contaminated by liquid solutions of radioactive isotopes 60Co, 133Ba, 152Eu and 241Am (A=12297.91 Bq/ml). Decontamination of contaminated samples was performed with 0.5% detergent solution on the basis of synthetic surfactants. The activity measurements of samples were conducted using gamma spectroscopy system with a high-resolution high-purity germanium (HPGe) detector of relative efficiency of 50% at 60Co (1.33 MeV). The degree of removal of the radioactivity on the samples was observed as an indicator of the efficiency of decontamination. A comparison of the results is presented in relation to the retention time of the contamination on the surface coating, which is an important factor for the efficiency of decontamination. The samples with an alkyd coating system showed better efficiency of decontamination than the samples with the epoxy-urethane coating system, although the coatings based on epoxy and urethane resin were superior in relation to the alkyd in terms of protection, decorative characteristics and chemical resistance. The difference in the efficiency of decontamination for the examined coatings increases almost linearly in relation to the retention time of the contaminants in the coating.

  1. The effect of hard/soft segment composition on radiation stability of poly(ester-urethane)s

    NASA Astrophysics Data System (ADS)

    Walo, Marta; Przybytniak, Grażyna; Łyczko, Krzysztof; Piątek-Hnat, Marta

    2014-01-01

    In this paper studies on the structures and radiation stability of four poly(ester-urethane)s (PUR)s synthesized from oligo(ethylene-butylene adipate)diol of various molecular weights and isophorone diisocyanate/1,4-butanediol are reported. PURs with 40 and 60 wt% soft segments were irradiated at ambient temperature with a high energy electron beam to a dose of 112 kGy. The effect of different segmental compositions on thermal and mechanical properties of polyurethanes, both before and after irradiation, were investigated using mechanical testing and dynamic mechanical thermal analysis. ATR-FTIR spectroscopy was used to study the progress of polycondensation, structure of synthesized polymers and extent of phase separation were determined on a basis of the contribution of hydrogen bonding in poly(ester-urethane)s. Correlation between degree of phase separation and mechanical and thermal properties of poly(ester-urethane)s was found.

  2. ASPECTS OF THE MECHNANICAL BEHAVIOR OF STITCHED T300 MAT/URETHANE 420 IMR COMPOSITE

    SciTech Connect

    Deng, S.

    2002-11-25

    This report presents experimental and analytical results concerning the behavior of crossply and quasi-isotropic laminates manufactured of stitch-bonded T300 urethane 420 IMR polymeric composites. Based on extensive creep and recovery data at various levels of stress and temperature, as well as on strain-to-failure information, it was possible to arrive at empirical expressions relating deformation to the previous input as well as to input duration. These expressions were incorporated within the formalisms of viscoelasticity and laminate theory to illuminate some basic underlying mechanistic aspects of the material at hand, thereby enabling the prediction of anticipated response under more complex stress and temperature inputs.

  3. Effects of Repeated Anesthesia Containing Urethane on Tumor Formation and Health Scores in Male C57BL/6J Mice.

    PubMed

    Rex, Tonia S; Boyd, Kelli; Apple, Troy; Bricker-Anthony, Courtney; Vail, Krystal; Wallace, Jeanne

    2016-01-01

    Repeated injection of urethane (ethyl carbamate) is carcinogenic in susceptible strains of mice. Most recent cancer studies involving urethane-induced tumor formation use p53(+/-) mice, which lack one copy of the p53 tumor suppressor gene. In contrast, the same protocol elicits at most a single tumor in wildtype C57BL/6 mice. The effect of repeatedly injecting urethane as a component of a ketamine-xylazine anesthetic mixture in the highly prevalent mouse strain C57BL/6 is unknown. Male C57BL/6J mice (n = 30; age, 3 mo) were anesthetized once monthly for 4 mo by using 560 mg/kg urethane, 28 mg/kg ketamine, and 5.6 mg/kg xylazine. The physical health of the mice was evaluated according to 2 published scoring systems. The average body condition score (scale, 1 to 5; normal, 3) was 3.3, 3.3, and 3.4 after the 2nd, 3rd, and 4th injections, respectively. The visual assessment score was 0 (that is, normal) at all time points examined. Within 1 wk after the 4th injection, the mice were euthanized, necropsied, and evaluated histopathologically. No histopathologic findings were noteworthy. We conclude that repeated monthly injection with urethane as a component of an anesthetic cocktail does not cause clinically detectable abnormalities or induce neoplasia in C57BL/6J mice. These findings are important because urethane combined with low-dose ketamine, unlike other anesthetic regimens, allows for accurate recording of neuronal activity in both the brain and retina. Longitudinal neuronal recordings minimize the number of mice needed and improve the analysis of disease progression and potential therapeutic interventions. PMID:27177562

  4. PH dependent adhesive peptides

    DOEpatents

    Tomich, John; Iwamoto, Takeo; Shen, Xinchun; Sun, Xiuzhi Susan

    2010-06-29

    A novel peptide adhesive motif is described that requires no receptor or cross-links to achieve maximal adhesive strength. Several peptides with different degrees of adhesive strength have been designed and synthesized using solid phase chemistries. All peptides contain a common hydrophobic core sequence flanked by positively or negatively charged amino acids sequences.

  5. Effects of model coal tar components on adhesion strength of polyurethane coating on steel plate

    SciTech Connect

    Yokoyama, N.; Fujino, K.

    2005-04-15

    In order to study the effects of coal tar components on the adhesion strength of a heavy duty anticorrosive coating formed with tar-urethane resin oil on a steel plate, polyurethane coatings that were compounded with 15 kinds of polycyclic aromatic compounds as model coal tar components were prepared. In the model coal tar, components, naphthalene, quinoline, 2-naphthol, and phenanthrene showed good compatibility with polyurethane. To test their heavy duty anticorrosive properties, tensile adhesion strength of the cured coatings prepared with the compatible model coal tar components was measured, and the change in tensile adhesion strength as a function of time during salt-water spray treatment was measured. We found that the systems compounded with naphthalene, 2-naphthol, and phenanthrene showed good properties in an ordinary state for adhesion strength. However, only the system with 2-naphthol was found to have good properties in the change of tensile adhesion strength as a function or time during salt-water spray treatment. The curing time of the system with 2-naphthol was slower than that or the others, i.e., we found an inverse proportion between curing speed and adhesion durability. We also measured the dynamic viscoelasticity of cured coatings.

  6. Structure/property behavior of a segmented poly(ester urethane) containing different hard segment contents

    SciTech Connect

    Orler, E. B.; Wrobleski, Debra A.; Campbell, M. S.

    2001-01-01

    A series of poly(ester urethanes) containing different hard segment contents were synthesized to provide information on the development of hard domain structure. In contrast to previous studies, this work focuses on segmented poly(ester urethanes) containing low hard segment contents. By incrementally increasing the hard segment content, we monitored the development of the hard domain structure using thermal analysis and x-ray diffraction. Rapid quenching of the samples from the melt shows that the hard and soft segments are miscible for all compositions at elevated temperatures. If the Tg of the mixed phase is greater than ambient temperature, the structure is trapped in a metastable mixed phase. Heating the materials above the Tg causes demixing and the Tg of the soft domain decreases. If the mixed phase Tg is below ambient conditions, the hard domains spontaneously phase separate. The alternating copolymer of poly(butylene adipate) (Mn = 1K) soft segment and methylene diisocyanate (MDI) (19% hard segment) shows high poly(butylene adipate) crystallinity. The addition of very small amounts of butanediol chain extender greatly inhibits soft segment crystallization. For hard segment compositions greater than 45%, hard domains crystallize.

  7. Controlled release of protein from biodegradable multi-sensitive injectable poly(ether-urethane) hydrogel.

    PubMed

    Li, Xiaomeng; Wang, Yangyun; Chen, Jiaming; Wang, Yinong; Ma, Jianbiao; Wu, Guolin

    2014-03-12

    The synthesis and characterization of multi-sensitive polymers for use as injectable hydrogels for controlled protein/drug delivery is reported. A series of biodegradable multi-sensitive poly(ether-urethane)s were prepared through a simple one-pot condensation of poly(ethylene glycol), 2,2'-dithiodiethanol, N-methyldiethanolamine, and hexamethylene diisocyanate. The sol-gel phase transition behaviors of the obtained copolymers were investigated. Experimental results showed that the aqueous medium comprising the multi-segment copolymers underwent a sol-to-gel phase transition with increasing temperature and pH. At a certain concentration, the copolymer solution could immediately change to a gel under physiological conditions (37 °C and pH 7.4), indicating their suitability as in situ injectable hydrogels in vivo. Insulin was used as a model protein drug for evaluation of the injectable hydrogels as a site-specific drug delivery system. The controlled release of insulin from the hydrogel devices was demonstrated by degradation of the copolymer, which is modulated via the 2,2'-dithiodiethanol content in the poly(ether-urethane)s. These hydrogels having multi-responsive properties may prove to be promising candidates for injectable and controllable protein drug delivery devices. PMID:24460175

  8. Does the Anesthetic Urethane Influence the Pharmacokinetics of Antifungal Drugs? A Population Pharmacokinetic Investigation in Rats.

    PubMed

    Azeredo, Francine Johansson; Hass, Sandra Elisa; Sansone, Pedro; Derendorf, Hartmut; Costa, Teresa Dalla; De Araujo, Bibiana Verlindo

    2015-10-01

    The aim of this paper was to analyze the impact of anesthesia induced by urethane on pharmacokinetics (PK) parameters of fluconazole (FCZ), mostly eliminated via renal excretion and voriconazole (VRC), eliminated mainly by hepatic metabolism. FCZ and VRC PK were investigated after administration of 10 mg/kg i.v. and 5 mg/kg i.v. doses to awake and urethane anesthetized Wistar rats (n = 6 per group), respectively. After dosing, blood samples were collected up to 18 h (FCZ) or 12 h (VRC) and the plasma data analysis was performed using the software MONOLIX v. 4.2.2. The population PK parameters and microconstants were determined by fitting plasma concentration-time profiles to two-compartment model for FCZ and three-compartment model for VRC. Fitting of FCZ plasma profiles after dosing to awake and anaesthetized animals resulted in a volume of distribution (V) of 9.3 and 8.1 L/kg, and k10 values of 0.12 and 0.14 h(-1) , respectively. VRC plasma profiles in awake and anaesthetized showed V 8.7 of and 7.6 L/kg, and k10 of 0.15 and 0.16 h(-1) , respectively. No statistical differences between plasma PK parameters and microconstants for the same drug in both animal conditions studied were observed (α = 0.05). PMID:26087701

  9. Effect of diisocyanate linkers on the degradation characteristics of copolyester urethanes as potential drug carrier matrices.

    PubMed

    Mathew, Simi; Baudis, Stefan; Neffe, Axel T; Behl, Marc; Wischke, Christian; Lendlein, Andreas

    2015-09-01

    In this study, the effect of three aliphatic diisocyanate linkers, L-lysine diisocyanate ethyl ester (LDI), hexamethylene diisocyanate (HDI), and racemic 2,2,4-/2,4,4-trimethyl hexamethylene diisocyanate (TMDI), on the degradation of oligo[(rac-lactide)-co-glycolide] (64:36 mol%) based polyester urethanes (PEU) was examined. Samples were characterized for their molecular weight, mass loss, water uptake, sequence structure, and thermal and mechanical properties. Compared to non-segmented PLGA, the PEU showed higher water uptake and generally degraded faster. Interestingly, the rate of degradation was not directly correlating with the hydrophilicity of the diisocyanate moieties; instead, competing intra-/intermolecular hydrogen bonds in between urethane moieties appear to substantially decrease the rate of degradation for LDI-derived PEU. By comparing microparticles (μm) and films (mm) as matrices of different dimensions, it was shown that autocatalysis remains a contributor to degradation of the larger-sized PEU matrices as it is typical for non-segmented lactide/glycolide copolymers. The shown capacity of lactide/glycolide-based multiblock copolymers to degrade faster than PLGA and exhibit improved elastic properties could be of interest for medical implants and drug release systems. PMID:25828207

  10. Effect of urethane, dimethylnitrosamine, paraquat, and butylated hydroxytoluene on the activities of glycolytic key enzymes in mouse lung

    SciTech Connect

    Arany, I.; Rady, P.; Bojan, I.; Kertai, P.

    1981-12-01

    Effects of carcinogens and noncarcinogenic pulmonary toxicants on the activities of glycolytic key enzymes in the mouse lung were investigated. The carcinogens urethane (URTH) and dimethylnitrosamine (DMN) permanently enhanced, and the noncarcinogenic pulmonary toxicants paraquat (PAR) and butylated hydroxytoluene (BHT) temporarily, enhanced the activities of hexokinase (HK), phosphofructokinase (PFK), and pyruvate kinase (PK) in the lungs of mice.

  11. IMMUNE FUNCTION IN ADULT C57BL/6J MICE FOLLOWING EXPOSURE TO URETHAN PRE- OR POSTNATALLY

    EPA Science Inventory

    Administration of urethan (URE or ethyl carbamate) to mice results in the development of a variety of tumors, and, in certain strains of mice, marked supression of the immune response. Perinatal exposure of mice to URE has been found to result in increased tumor induction compare...

  12. Firing relations of medial entorhinal neurons to the hippocampal theta rhythm in urethane anesthetized and walking rats.

    PubMed

    Stewart, M; Quirk, G J; Barry, M; Fox, S E

    1992-01-01

    The firing of neurons from layers II and III of medial entorhinal cortex (MEC) was examined in relation to the hippocampal theta rhythm in urethane anesthetized and walking rats. 1) MEC neurons showed a significant phase relation to the hippocampal theta rhythm in both walking and urethane anesthetized rats, suggesting that this region contributes to the generation of both atropine-resistant and atropine-sensitive theta rhythm components. 2) The proportion of phase-locked cells was three times greater in walking rats (22/23 cells) as compared to anesthetized rats (8/23 cells), indicating that MEC cells made a greater contribution during walking theta rhythm. This difference was also manifest in the greater mean vector length for the group of phase-locked MEC cells during walking: 0.39 +/- 0.13 versus 0.21 +/- 0.08. Firing rate differences between walking and urethane conditions were not significant. 3) In walking rats, MEC cells fired on the positive peak of the dentate theta rhythm (group mean phase = 5 degrees; 0 degrees = positive peak at the hippocampal fissure). This is close to the reported phases for dentate granule and hippocampal pyramidal cells. The distribution of MEC cell phases in urethane anesthetized rats was broader (group mean phase = 90 degrees), consistent with the phase data reported for hippocampal projection cells. These findings suggest that medial entorhinal neurons are the principal determinant of theta-related firing of hippocampal neurons and that their robust rhythmicity in walking as compared to urethane anesthesia accounts for EEG differences across the two conditions. PMID:1521610

  13. A Simple and Novel Method to Monitor Breathing and Heart Rate in Awake and Urethane-Anesthetized Newborn Rodents

    PubMed Central

    Zehendner, Christoph M.; Luhmann, Heiko J.; Yang, Jenq-Wei

    2013-01-01

    Rodents are most useful models to study physiological and pathophysiological processes in early development, because they are born in a relatively immature state. However, only few techniques are available to monitor non-invasively heart frequency and respiratory rate in neonatal rodents without restraining or hindering access to the animal. Here we describe experimental procedures that allow monitoring of heart frequency by electrocardiography (ECG) and breathing rate with a piezoelectric transducer (PZT) element without hindering access to the animal. These techniques can be easily installed and are used in the present study in unrestrained awake and anesthetized neonatal C57/Bl6 mice and Wistar rats between postnatal day 0 and 7. In line with previous reports from awake rodents we demonstrate that heart rate in rats and mice increases during the first postnatal week. Respiratory frequency did not differ between both species, but heart rate was significantly higher in mice than in rats. Further our data indicate that urethane, an agent that is widely used for anesthesia, induces a hypoventilation in neonates whilst heart rate remains unaffected at a dose of 1 g per kg body weight. Of note, hypoventilation induced by urethane was not detected in rats at postnatal 0/1. To verify the detected hypoventilation we performed blood gas analyses. We detected a respiratory acidosis reflected by a lower pH and elevated level in CO2 tension (pCO2) in both species upon urethane treatment. Furthermore we found that metabolism of urethane is different in P0/1 mice and rats and between P0/1 and P6/7 in both species. Our findings underline the usefulness of monitoring basic cardio-respiratory parameters in neonates during anesthesia. In addition our study gives information on developmental changes in heart and breathing frequency in newborn mice and rats and the effects of urethane in both species during the first postnatal week. PMID:23658756

  14. Fabrication and Normal/Shear Stress Responses of Tactile Sensors of Polymer/Si Cantilevers Embedded in PDMS and Urethane Gel Elastomers

    NASA Astrophysics Data System (ADS)

    Huang, Yu Ming; Sohgawa, Masayuki; Yamashita, Kaoru; Kanashima, Takeshi; Okuyama, Masanori; Noda, Minoru; Noma, Haruo

    Cantilever-type tactile sensors of silicon-polymer beam structures were fabricated by surface micromachining and covering with elastomers. Two kinds of elastomers with different Young's modulus PDMS and urethane gel have been used to control deflection of the cantilevers and adjust the sensitivity cantilever-type tactile sensors. The resistance change of the sensor with PDMS has linear dependence on normal and shear stresses, but that of the sensor with urethane gel is nonliner to normal and shear stresses. However, the sensitivity of urethane gel type sensor is about 30 times larger than PDMS type sensor.

  15. Surface decorated poly(ester-ether-urethane)s nanoparticles: a versatile approach towards clinical translation.

    PubMed

    Piras, Anna Maria; Sandreschi, Stefania; Malliappan, Sivakumar Ponnurengam; Dash, Mamoni; Bartoli, Cristina; Dinucci, Dinuccio; Guarna, Francesco; Ammannati, Enrico; Masa, Marc; Múčková, Marta; Schmidtová, Ludmila; Chiellini, Emo; Chiellini, Federica

    2014-11-20

    Poly(ester-ether-urethane)s copolymers are a resourceful class of biopolymers for the preparation of nanocarriers for drug delivery applications. However, a simple clinical translation for this synthetic material with biological and quality features is still needed. In this view, poly(ε-caprolactone)-co-poly(ethylene glycol) copolymers were synthesized as semi-bulk pilot (Kg) scale under mild conditions in absence of catalyst, bearing functional termini such as fluorescein tag and anticancer targeting moieties. The obtained materials were processed into surface decorated paclitaxel (PTX) loaded nanoparticles (NPs). The NPs were fully characterized in vitro and in vivo biodistribution in healthy mice evidenced no sign of toxicity and lower levels of PTX in lung and spleen, compared to clinically applied PTX dosage form. PMID:25178828

  16. Humidity-dependent dynamic infrared linear dichroism study of a poly(ester urethane).

    PubMed

    Schoonover, Jon R; Steckle, Warren P; Cox, Jonathan D; Johnston, Cliff T; Wang, Yanqia; Gillikin, Angela M; Palmer, Richard A

    2007-05-01

    Fourier transform infrared techniques, infrared difference spectroscopy and dynamic infrared linear dichroism (DIRLD), have been utilized to explore the effects of humidity and water absorption on a poly(ester urethane). An environmental infrared microbalance cell was used to measure the infrared spectra as a function of humidity and accompanying weight change for the absorption-desorption processes. The infrared difference data indicate that exposure to humidity affects the hydrogen-bonding interactions in the polymer. Dynamic infrared linear dichroism studies in tensile deformation mode as a function of humidity demonstrate how changes in water content affect the orientational response of functional groups. Complex behavior as a function of humidity for functional groups involved in hydrogen bonding indicates that water absorbed by the polymer affects the micro-environments near these functional groups. PMID:16950649

  17. Surface modification of a biomedical poly(ether)urethane by a remote air plasma

    NASA Astrophysics Data System (ADS)

    Gray, J. E.; Norton, P. R.; Griffiths, K.

    2003-07-01

    Plasma modification of polymer surfaces is widely used, but the plasma/polymer interaction is very complex and still not fully understood. In this paper, the interaction of a biomedical poly(ether)urethane with a remote air plasma treatment has been studied. Atomic force microscopy studies show the domain structure of the polymer as well as the absence of any surface roughening due to plasma treatment. Contact angle goniometry shows an improved wettability of the surface after plasma treatment. X-ray photoelectron spectroscopy indicates an increase in CO and CC at the surface, as well as the presence of new functional groups such as alcohols, ketones, aldehydes and imines. There is also evidence that the energy imparted to the polymer during plasma treatment causes surface segregation of polyol segments.

  18. Low loading of carbon nanotubes to enhance acoustical properties of poly(ether)urethane foams

    NASA Astrophysics Data System (ADS)

    Basirjafari, Sedigheh; Malekfar, Rasoul; Esmaielzadeh Khadem, Siamak

    2012-11-01

    The aim of this paper is to fabricate a sound absorber flexible semi-open cell polymeric foam based on polyether urethane (PEU) with carboxylic functionalized multi-walled carbon nanotubes (COOH-MWCNTs) as an energy decaying filler at low loadings up to 0.20 wt. %. This paper provides the relationship between the mentioned foam microstructure via field emission scanning electron microscopy and different acoustical and non-acoustical properties of PEU/COOH-MWCNT composites. Addition of just 0.05 wt. % COOH-MWCNTs enhanced the sound absorption coefficient of the mentioned nanocomposite foam over the entire frequency range. Raman spectra revealed the better dispersion of COOH-MWCNTs in the PEU matrix leading to more stress transfer between them to cause a significant dissipation of energy.

  19. Photoinduced Phase Transition in Single Crystals on Urethane-Sustituted Polydiacetylenes

    NASA Astrophysics Data System (ADS)

    Tachibana, Hiroaki; Hosaka, Noriko; Osaki, Masayuki; Tokura, Yoshinori

    Thermochromic behaviors were investigated by measurements of reflectance spectra for urethane-substituted polydiacetylene crystal having side groups of R=(CH)2)6OCONHC2H5 (PDA-6UEt). The PDA-6UEt crystal shows an irreversible thermochromic A-to-B (blue-to-red) phase transition: the absorption band at 1.88 eV due to the lowest exciton shifts to higher energy (2.15 eV) in the heating run, but the reflectance spectra remain in the B phase even when cooled down to room temperature. We have demonstrated that photoinduced phase transition (PIPT) is observed by utilizing the irreversible A-to-B phase transition. The conversion shows the presence of a threshold of the light intensity and depends on photon energy, suggesting that the PIPT is mediated by the photogenerated electron-hole pairs.

  20. Reversible and irreversible thermochromic phase transitions in single crystals of polydiacetylenes substituted with alkyl-urethanes

    NASA Astrophysics Data System (ADS)

    Koshihara, Shin-ya; Tokura, Yoshinori; Takeda, Kenji; Koda, Takao; Kobayashi, Akiko

    1990-06-01

    Reversible transitions between the two spectroscopically distinct phases (A and B phases) have been investigated for a new family of polydiacetylenes (PDAs) substituted with side groups of alkyl-urethane [-(CH2)4OCONH(CH2)n-1CH3:n =1-10]. Measurements of optical spectra as well as x-ray and calorimetric studies have revealed the first-order-like phase transitions in a series of PDAs with n=1-10 which are associated with an n-dependent thermal hysteresis ranging from 0 to 60 K in width. It has been found that the thermochromic changes become irreversible in all these PDAs once the hydrogen bond chains in the side groups are interrupted by heating beyond the polymer melting temperature.

  1. Photoinduced Phase Transition in Single Crystals of Urethane-Substituted Polydiacetylenes

    NASA Astrophysics Data System (ADS)

    Tachibana, Hiroaki; Hosaka, Noriko; Osaki, Masayuki; Tokura, Yoshinori

    2001-08-01

    Thermochromic behaviors were investigated by measurements of reflectance spectra for urethane-substituted polydiacetylene crystal having side groups of R=(CH2)6OCONHC2H5 (PDA-6UEt). The PDA-6UEt crystal shows an irreversible thermochromic A-to-B (blue-to-red) phase transition: the absorption band at 1.88 eV due to the lowest exciton shifts to higher energy (2.15 eV) in the heating run, but the reflectance spectra remain in the B phase even when cooled down to room temperature. We have demonstrated that photoinduced phase transition (PIPT) is observed by utilizing the irreversible A-to-B phase transition. The conversion shows the presence of a threshold of the light intensity and depends on photon energy, suggesting that the PIPT is mediated by the photogenerated electron-hole pairs.

  2. Chemical and Physical Changes in a Hydrolyzed Poly(ester urethane)

    SciTech Connect

    ASSINK,ROGER A.; CELINA,MATHIAS C.; LANG,DAVID P.

    1999-11-03

    Hydrolytic degradation has been shown to be a significant problem for poly(ester urethane) elastomers exposed to high humidity environments. The ester group in the soft segment is particularly susceptible to hydrolysis. One of the products of this reaction is a carboxylic acid group that catalyses further hydrolysis. The resulting reduction in molecular weight leads to deterioration of the elastomer's mechanical properties. In this paper we have measured the extent of the hydrolysis reaction by {sup 13}C NMR spectroscopy. In addition we have measured the spin-spin relaxation time of the soft phase and followed the increase in mobility of these segments. Both measurements were performed on the solid polymer. These measurements provide an excellent monitoring tool of the chemical and physical state of polymer during the aging process.

  3. Urethane-based stabilizers for radiation-crosslinked polyethylene. [Electron beams

    SciTech Connect

    Shkolnik, S.; Rajbenbach, L.A.

    1982-11-01

    Unsaturated urethane-based stabilizers for use in radiation-crosslinked polyethylene were synthesized. Aromatic amine moieties were attached to allylic and acrylic monomers by means of aromatic or aliphatic diisocyanates. The synthesized stabilizers were incorporated in high-density polyethylene films which were subjected to electron beam irradiation. The oxidative stability of the films prior to and after extraction was determined by DTA in the temperature range 185-210/sup 0/C and compared with samples treated with commercial amine-bearing antioxidants. Tensile strength and gel content were also determined. Best results were obtained with a stabilizer prepared from equimolecular amounts of allyl alcohol, tolylene-2,4-diisocyanate and N-phenyl-1,4-phenylenediamine. Estimated lifetimes at 70/sup 0/C of stabilized irradiated polyethylene samples were calculated.

  4. Highly selective and stable florescent sensor for Cd(II) based on poly (azomethine-urethane).

    PubMed

    Kaya, İsmet; Kamacı, Musa

    2013-01-01

    In this study a kind of poly(azomethine-urethane); (E)-4-((2 hydroxyphenylimino) methyl)-2-methoxyphenyl 6-acetamidohexylcarbamate (HDI-co-3-DHB-2-AP) was prepared as in the literature and employed as a new fluorescent probe for detection of Cd(II) concentration. The photoluminescence (PL) measurements were carried out in the presence of several kinds of heavy metals. HDI-co-3-DHB-2-AP gave a linearly and highly stable response against Cd(II) as decreasing a new emission peak at 562 nm. Possible interferences of other ions were found too low. Detection limit of the sensor was found as 8.86 × 10(-4) mol L(-1). Resultantly, HDI-co-3- DHB-2-AP could be effectively used as an optical Cd(II) sensor. PMID:22941725

  5. Poly(glycerol sebacate urethane)-cellulose nanocomposites with water-active shape-memory effects.

    PubMed

    Wu, Tongfei; Frydrych, Martin; O'Kelly, Kevin; Chen, Biqiong

    2014-07-14

    Biodegradable and biocompatible materials with shape-memory effects (SMEs) are attractive for use as minimally invasive medical devices. Nanocomposites with SMEs were prepared from biodegradable poly(glycerol sebacate urethane) (PGSU) and renewable cellulose nanocrystals (CNCs). The effects of CNC content on the structure, water absorption, and mechanical properties of the PGSU were studied. The water-responsive mechanically adaptive properties and shape-memory performance of PGSU-CNC nanocomposites were observed, which are dependent on the content of CNCs. The PGSU-CNC nanocomposite containing 23.2 vol % CNCs exhibited the best SMEs among the nanocomposites investigated, with the stable shape fixing and shape recovery ratios being 98 and 99%, respectively, attributable to the formation of a hydrophilic, yet strong, CNC network in the elastomeric matrix. In vitro degradation profiles of the nanocomposites were assessed with and without the presence of an enzyme. PMID:24877559

  6. Humidity-dependent dynamic infrared linear dichroism study of a poly(ester urethane)

    NASA Astrophysics Data System (ADS)

    Schoonover, Jon R.; Steckle, Warren P., Jr.; Cox, Jonathan D.; Johnston, Cliff T.; Wang, Yanqia; Gillikin, Angela M.; Palmer, Richard A.

    2007-05-01

    Fourier transform infrared techniques, infrared difference spectroscopy and dynamic infrared linear dichroism (DIRLD), have been utilized to explore the effects of humidity and water absorption on a poly(ester urethane). An environmental infrared microbalance cell was used to measure the infrared spectra as a function of humidity and accompanying weight change for the absorption-desorption processes. The infrared difference data indicate that exposure to humidity affects the hydrogen-bonding interactions in the polymer. Dynamic infrared linear dichroism studies in tensile deformation mode as a function of humidity demonstrate how changes in water content affect the orientational response of functional groups. Complex behavior as a function of humidity for functional groups involved in hydrogen bonding indicates that water absorbed by the polymer affects the micro-environments near these functional groups.

  7. Reversible Thermoset Adhesives

    NASA Technical Reports Server (NTRS)

    Mac Murray, Benjamin C. (Inventor); Tong, Tat H. (Inventor); Hreha, Richard D. (Inventor)

    2016-01-01

    Embodiments of a reversible thermoset adhesive formed by incorporating thermally-reversible cross-linking units and a method for making the reversible thermoset adhesive are provided. One approach to formulating reversible thermoset adhesives includes incorporating dienes, such as furans, and dienophiles, such as maleimides, into a polymer network as reversible covalent cross-links using Diels Alder cross-link formation between the diene and dienophile. The chemical components may be selected based on their compatibility with adhesive chemistry as well as their ability to undergo controlled, reversible cross-linking chemistry.

  8. Adhesion at metal interfaces

    NASA Technical Reports Server (NTRS)

    Banerjea, Amitava; Ferrante, John; Smith, John R.

    1991-01-01

    A basic adhesion process is defined, the theory of the properties influencing metallic adhesion is outlined, and theoretical approaches to the interface problem are presented, with emphasis on first-principle calculations as well as jellium-model calculations. The computation of the energies of adhesion as a function of the interfacial separation is performed; fully three-dimensional calculations are presented, and universality in the shapes of the binding energy curves is considered. An embedded-atom method and equivalent-crystal theory are covered in the framework of issues involved in practical adhesion.

  9. Preparation of Sticky Escherichia coli through Surface Display of an Adhesive Catecholamine Moiety

    PubMed Central

    Park, Joseph P.; Choi, Min-Jung; Kim, Se Hun

    2014-01-01

    Mussels attach to virtually all types of inorganic and organic surfaces in aqueous environments, and catecholamines composed of 3,4-dihydroxy-l-phenylalanine (DOPA), lysine, and histidine in mussel adhesive proteins play a key role in the robust adhesion. DOPA is an unusual catecholic amino acid, and its side chain is called catechol. In this study, we displayed the adhesive moiety of DOPA-histidine on Escherichia coli surfaces using outer membrane protein W as an anchoring motif for the first time. Localization of catecholamines on the cell surface was confirmed by Western blot and immunofluorescence microscopy. Furthermore, cell-to-cell cohesion (i.e., cellular aggregation) induced by the displayed catecholamine and synthesis of gold nanoparticles on the cell surface support functional display of adhesive catecholamines. The engineered E. coli exhibited significant adhesion onto various material surfaces, including silica and glass microparticles, gold, titanium, silicon, poly(ethylene terephthalate), poly(urethane), and poly(dimethylsiloxane). The uniqueness of this approach utilizing the engineered sticky E. coli is that no chemistry for cell attachment are necessary, and the ability of spontaneous E. coli attachment allows one to immobilize the cells on challenging material surfaces such as synthetic polymers. Therefore, we envision that mussel-inspired catecholamine yielded sticky E. coli that can be used as a new type of engineered microbe for various emerging fields, such as whole living cell attachment on versatile material surfaces, cell-to-cell communication systems, and many others. PMID:24123747

  10. Preparation of sticky Escherichia coli through surface display of an adhesive catecholamine moiety.

    PubMed

    Park, Joseph P; Choi, Min-Jung; Kim, Se Hun; Lee, Seung Hwan; Lee, Haeshin

    2014-01-01

    Mussels attach to virtually all types of inorganic and organic surfaces in aqueous environments, and catecholamines composed of 3,4-dihydroxy-l-phenylalanine (DOPA), lysine, and histidine in mussel adhesive proteins play a key role in the robust adhesion. DOPA is an unusual catecholic amino acid, and its side chain is called catechol. In this study, we displayed the adhesive moiety of DOPA-histidine on Escherichia coli surfaces using outer membrane protein W as an anchoring motif for the first time. Localization of catecholamines on the cell surface was confirmed by Western blot and immunofluorescence microscopy. Furthermore, cell-to-cell cohesion (i.e., cellular aggregation) induced by the displayed catecholamine and synthesis of gold nanoparticles on the cell surface support functional display of adhesive catecholamines. The engineered E. coli exhibited significant adhesion onto various material surfaces, including silica and glass microparticles, gold, titanium, silicon, poly(ethylene terephthalate), poly(urethane), and poly(dimethylsiloxane). The uniqueness of this approach utilizing the engineered sticky E. coli is that no chemistry for cell attachment are necessary, and the ability of spontaneous E. coli attachment allows one to immobilize the cells on challenging material surfaces such as synthetic polymers. Therefore, we envision that mussel-inspired catecholamine yielded sticky E. coli that can be used as a new type of engineered microbe for various emerging fields, such as whole living cell attachment on versatile material surfaces, cell-to-cell communication systems, and many others. PMID:24123747

  11. Characterization of the Degradation Mechanisms of Lysine-derived Aliphatic Poly(ester urethane) Scaffolds

    PubMed Central

    Hafeman, Andrea E.; Zienkiewicz, Katarzyna J.; Zachman, Angela L.; Sung, Hak-Joon; Nanney, Lillian B.; Davidson, Jeffrey M.; Guelcher, Scott A.

    2010-01-01

    Characterization of the degradation mechanism of polymeric scaffolds and delivery systems for regenerative medicine is essential to assess their clinical applicability. Key performance criteria include induction of a minimal, transient inflammatory response and controlled degradation to soluble non-cytotoxic breakdown products that are cleared from the body by physiological processes. Scaffolds fabricated from biodegradable poly(ester urethane)s (PEURs) undergo controlled degradation to non-cytotoxic breakdown products and support the ingrowth of new tissue in preclinical models of tissue regeneration. While previous studies have shown that PEUR scaffolds prepared from lysine-derived polyisocyanates degrade faster under in vivo compared to in vitro conditions, the degradation mechanism is not well understood. In this study, we have shown that PEUR scaffolds prepared from lysine triisocyanate (LTI) or a trimer of hexamethylene diisocyanate (HDIt) undergo hydrolytic, esterolytic, and oxidative degradation. Hydrolysis of ester bonds to yield α-hydroxy acids is the dominant mechanism in buffer, and esterolytic media modestly increase the degradation rate. While HDIt scaffolds show a modest (<20%) increase in degradation rate in oxidative medium, LTI scaffolds degrade six times faster in oxidative medium. Furthermore, the in vitro rate of degradation of LTI scaffolds in oxidative medium approximates the in vivo rate in rat excisional wounds, and histological sections show macrophages expressing myeloperoxidase at the material surface. While recent preclinical studies have underscored the potential of injectable PEUR scaffolds and delivery systems for tissue regeneration, this promising class of biomaterials has a limited regulatory history. Elucidation of the macrophage-mediated oxidative mechanism by which LTI scaffolds degrade in vivo provides key insights into the ultimate fate of these materials when injected into the body. PMID:20864156

  12. Characterization of the degradation mechanisms of lysine-derived aliphatic poly(ester urethane) scaffolds.

    PubMed

    Hafeman, Andrea E; Zienkiewicz, Katarzyna J; Zachman, Angela L; Sung, Hak-Joon; Nanney, Lillian B; Davidson, Jeffrey M; Guelcher, Scott A

    2011-01-01

    Characterization of the degradation mechanism of polymeric scaffolds and delivery systems for regenerative medicine is essential to assess their clinical applicability. Key performance criteria include induction of a minimal, transient inflammatory response and controlled degradation to soluble non-cytotoxic breakdown products that are cleared from the body by physiological processes. Scaffolds fabricated from biodegradable poly(ester urethane)s (PEURs) undergo controlled degradation to non-cytotoxic breakdown products and support the ingrowth of new tissue in preclinical models of tissue regeneration. While previous studies have shown that PEUR scaffolds prepared from lysine-derived polyisocyanates degrade faster under in vivo compared to in vitro conditions, the degradation mechanism is not well understood. In this study, we have shown that PEUR scaffolds prepared from lysine triisocyanate (LTI) or a trimer of hexamethylene diisocyanate (HDIt) undergo hydrolytic, esterolytic, and oxidative degradation. Hydrolysis of ester bonds to yield α-hydroxy acids is the dominant mechanism in buffer, and esterolytic media modestly increase the degradation rate. While HDIt scaffolds show a modest (<20%) increase in degradation rate in oxidative medium, LTI scaffolds degrade six times faster in oxidative medium. Furthermore, the in vitro rate of degradation of LTI scaffolds in oxidative medium approximates the in vivo rate in rat excisional wounds, and histological sections show macrophages expressing myeloperoxidase at the material surface. While recent preclinical studies have underscored the potential of injectable PEUR scaffolds and delivery systems for tissue regeneration, this promising class of biomaterials has a limited regulatory history. Elucidation of the macrophage-mediated oxidative mechanism by which LTI scaffolds degrade in vivo provides key insights into the ultimate fate of these materials when injected into the body. PMID:20864156

  13. Surface modification of poly(ether urethane urea) with modified dehydroepiandrosterone for improved in vivo biostability.

    PubMed

    Christenson, Elizabeth M; Wiggins, Michael J; Anderson, James M; Hiltner, Anne

    2005-04-01

    In this study, a fatty acid urethane derivative of dehydroepiandrosterone (DHEA) was synthesized and evaluated as a polyurethane additive to increase long-term biostability. The modification was hypothesized to reduce the water solubility of the DHEA and physically anchor the additive in the polyurethane during implantation. Polyurethane film weight loss in water as a function of time was studied to determine the polymer retention of the modified DHEA. The polyurethane film with unmodified DHEA had significant weight loss in the first day (10%) that was previously correlated to rapid leaching of the additive. The polyurethane film with modified DHEA had significantly less weight loss at all time points indicating improved polymer retention. The effect of the modified DHEA additive on the biostability of a poly(ether urethane urea) was examined after 5 weeks of subcutaneous implantation in Sprague-Dawley rats. Optical micrographs and infrared analysis of the specimens indicated that the modified DHEA bloomed to the surface of the film forming a crystalline surface layer approximately 10-15 microns thick. After explantation, this surface layer was intact without measurable differences in surface chemistry as monitored by attenuated total reflectance-Fourier transform infrared spectroscopy. There was no evidence of degradation of the polyurethane underneath the modified DHEA surface layer as compared with the polyurethane control. We have concluded that the modified DHEA self-assembled into a protective surface coating that inhibited degradation of the polyurethane. The roughness of the modified DHEA surface layer prevented adherent cell analysis to determine if the additive retained the ability to down-regulate macrophage activity. Subsequent studies will investigate the ability of surface-modifying additives to modulate cellular respiratory bursts in addition to the formation of an impermeable barrier. This bimodal approach to improving biostability holds great

  14. Characterization of a resorbable poly(ester urethane) with biodegradable hard segments.

    PubMed

    Dempsey, David K; Robinson, Jennifer L; Iyer, Ananth V; Parakka, James P; Bezwada, Rao S; Cosgriff-Hernandez, Elizabeth M

    2014-01-01

    The rapid growth of regenerative medicine and drug delivery fields has generated a strong need for improved polymeric materials that degrade at a controlled rate into safe, non-cytotoxic by-products. Polyurethane thermoplastic elastomers offer several advantages over other polymeric materials including tunable mechanical properties, excellent fatigue strength, and versatile processing. The variable segmental chemistry in developing resorbable polyurethanes also enables fine control over the degradation profile as well as the mechanical properties. Linear aliphatic isocyanates are most commonly used in biodegradable polyurethane formulations; however, these aliphatic polyurethanes do not match the mechanical properties of their aromatic counterparts. In this study, a novel poly(ester urethane) (PEsU) synthesized with biodegradable aromatic isocyanates based on glycolic acid was characterized for potential use as a new resorbable material in medical devices. Infrared spectral analysis confirmed the aromatic and phase-separated nature of the PEsU. Uniaxial tensile testing displayed stress-strain behavior typical of a semi-crystalline polymer above its Tg, in agreement with calorimetric findings. PEsU outperformed aliphatic PCL-based polyurethanes likely due to the enhanced cohesion of the aromatic hard domains. Accelerated degradation of the PEsU using 0.1 M sodium hydroxide resulted in hydrolysis of the polyester soft segment on the surface, reduced molecular weight, surface cracking, and a 30% mass loss after four weeks. Calorimetric studies indicated a disruption of the soft segment crystallinity after incubation which corresponded with a drop in initial modulus of the PEsU. Finally, cytocompatibility testing with 3T3 mouse fibroblasts exhibited cell viability on PEsU films comparable to a commercial poly(ether urethane urea) after 24 h followed by 85% cell viability at 72 h. Overall, this new resorbable polyurethane shows strong potential for use in wide

  15. Comparative analysis of in vitro oxidative degradation of poly(carbonate urethanes) for biostability screening.

    PubMed

    Dempsey, David K; Carranza, Christopher; Chawla, Chander P; Gray, Patrick; Eoh, Joon H; Cereceres, Stacy; Cosgriff-Hernandez, Elizabeth M

    2014-10-01

    The resistance to oxidation and environmental stress cracking of poly(carbonate urethanes) (PCUs) has generated significant interest as potential replacements of poly(ether urethanes) in medical devices. Several in vitro models have been developed to screen segmented polyurethanes for oxidative stability. High concentrations of reactive oxygen intermediates produced by combining hydrogen peroxide and dissolved cobalt ions has frequently been used to predict long-term oxidative degradation with short-term testing. Alternatively, a 3% H₂O₂ concentration without metal ions is suggested within the ISO 10993-13 standard to simulate physiological degradation rates. A comparative analysis which evaluates the predictive capabilities of each test method has yet to be completed. To this end, we have utilized both systems to test three commercially available PCUs with low and high soft segment content: Bionate PCU and Bionate II PCUs, two materials with different soft segment chemistries, and CarboSil TSPCU, a thermoplastic silicone PCU. Bulk properties of all PCUs were retained with minor changes in molecular weight and tensile properties indicating surface oxidative degradation in the accelerated system after 36 days. Soft segment loss and surface damage were comparable to previous in vivo data. The 3% H₂O₂ method exhibited virtually no changes on the surface or in bulk properties after 12 months of treatment despite previous in vivo results. These results indicate the accelerated test method more effectively characterized the oxidative degradation profiles than the 3% H₂O₂ treatment system. The lack of bulk degradation in the 12-month study also supports the hydrolytic stability of these PCUs. PMID:24265203

  16. Sex-Related Differences in the Sensitivity to Carcinogenic Effect of Urethane on the Lungs in Mice Are Reversed after Neonatal Androgenization.

    PubMed

    Morozkova, T S; Kaledin, V I

    2015-10-01

    Experiments on male and female CC57BR/Mv mice differing by the sensitivity to carcinogenic effect of urethane on the lungs showed that castration 1 week before carcinogen challenge reduced the number of lung adenomas caused by it in males and somewhat increased the number of tumors in females. Exogenous testosterone after urethane injection caused virtually no changes in urethane effect in males and females. By contrast, elevation of testosterone concentrations in newborn male and female mice by injections or its decrease in feminized males receiving sodium glutamate during the neonatal period reduced the sensitivity to the carcinogenic effect of urethane in adult males and to its increase in females. PMID:26515180

  17. Design, synthesis and 1H NMR study of C3v-symmetric anion receptors with urethane-NH as recognition group

    NASA Astrophysics Data System (ADS)

    Park, Jin-Oh; Sahoo, Suban K.; Choi, Heung-Jin

    2016-01-01

    C3v-Symmetric anion receptors 3 and 4 with urethane groups were synthesized by using trindane triol as tripodal molecular framework. In 1H NMR titration study, the receptors showed noticeable downfield shift/disappearance of the urethane-NH peak in presence of H2PO4- and F- due to the host-guest complexation occurred through multiple hydrogen bonding and/or the deprotonation of urethane-NH groups. Other tested anions such as Cl-, Br-, HSO4-, and NO3- showed either no or negligible chemical shift of the urethane groups. The deprotonation event in 4 allowed selective detection of F- by perceptible color change from colorless to yellowish-red with the appearance of a new charge transfer absorption band at 450 nm.

  18. Postoperative Peritoneal Adhesions

    PubMed Central

    Ryan, Graeme B.; Grobéty, Jocelyne; Majno, Guido

    1971-01-01

    This paper describes an experimental model of peritoneal adhesions, in the rat, based on two relatively minor accidents that may occur during abdominal surgery in man: drying of the serosa, and bleeding. Drying alone had little effect; drying plus bleeding consistently produced adhesions to the dried area. Fresh blood alone produced adhesions between the three membranous structures [omentum and pelvic fat bodies (PFBs)]. The formation of persistent adhesions required whole blood. Preformed clots above a critical size induced adhesions even without previous serosal injury; they were usually captured by the omentum and PFBs. If all three membranous structures were excised, the clots caused visceral adhesions. The protective role of the omentum, its structure, and the mechanism of omental adhesions, are discussed. These findings are relevant to the pathogenesis of post-operative adhesions in man. ImagesFig 3Fig 4Fig 5Fig 6Fig 7Fig 12Fig 13Fig 1Fig 2Fig 14Fig 15Fig 8Fig 9Fig 10Fig 11 PMID:5315369

  19. Simultaneous time-resolved synchrotron X-ray scattering studies on block copoly(ether-urethane) phase behaviour

    NASA Astrophysics Data System (ADS)

    Naylor, S.; Bras, W.; Derbyshire, G.; Mant, G. R.; Bogg, D.; Ryan, A. J.

    1995-05-01

    New experimental techniques for the characterisation of the thermal-morphological properties of materials have been developed at Daresbury. Many thermal events, for example, melting endotherms, are signals of changes in morphology covering size scales from the atomic to the microscopic, that isÅto μm. There are several advantages in collecting both the wide angle (1 to 20Å) and small angle (20 to 1000Å) patterns simultaneously, along with the DSC trace, to unambiguously characterise such thermal events. New apparatus has been built at Daresbury, consisting of a modified Linkam DSC hot-stage mounted in a combined SAXS/WAXS camera to carry out such studies. In addition, equipment has been assembled to assess the feasibility of combining FTIR and SAXS/WAXS to study structural changes in various poly(ether urethane)s.

  20. Cytotoxicity of denture adhesives.

    PubMed

    de Gomes, Pedro Sousa; Figueiral, Maria Helena; Fernandes, Maria Helena R; Scully, Crispian

    2011-12-01

    Ten commercially available denture adhesives, nine soluble formulations (six creams, three powders) and one insoluble product (pad), were analyzed regarding the cytotoxicity profile in direct and indirect assays using L929 fibroblast cells. In the direct assay, fibroblasts were seeded over the surface of a thick adhesive gel (5%, creams; 2.5%, powders and pad). In the indirect assay, cells were cultured in the presence of adhesive extracts prepared in static and dynamic conditions (0.5-2%, creams; 0.25-1%, powders and pad). Cell toxicity was assessed for cell viability/proliferation (MTT assay) and cell morphology (observation of the F-actin cytoskeleton organization by confocal laser scanning microscopy). Direct contact of the L929 fibroblasts with the thick adhesive gels caused no, or only a slight, decrease in cell viability/proliferation. The adhesive extracts (especially those prepared in dynamic conditions) caused significantly higher growth inhibition of fibroblasts and, in addition, caused dose- and time-dependent effects, throughout the 6-72 h exposure time. Also, dose-dependent effects on cell morphology, with evident disruption of the F-actin cytoskeleton organization, were seen in the presence of most adhesives. In conclusion, the adhesives possessed different degrees of cytotoxicity, but similar dose- and time-dependent biological profiles. PMID:20844908

  1. Biodegradable gadolinium-chelated cationic poly(urethane amide) copolymers for gene transfection and magnetic resonance imaging.

    PubMed

    Gao, Xiaolong; Wang, Gangmin; Shi, Ting; Shao, Zhihong; Zhao, Peng; Shi, Donglu; Ren, Jie; Lin, Chao; Wang, Peijun

    2016-08-01

    Theranostic nano-polyplexes containing gene and imaging agents hold a great promise for tumor diagnosis and therapy. In this work, we develop a group of new gadolinium (Gd)-chelated cationic poly(urethane amide)s for gene delivery and T1-weighted magnetic resonance (MR) imaging. Cationic poly(urethane amide)s (denoted as CPUAs) having multiple disulfide bonds, urethane and amide linkages were synthesized by stepwise polycondensation reaction between 1,4-bis(3-aminopropyl)piperazine and a mixture of di(4-nitrophenyl)-2, 2'-dithiodiethanocarbonate (DTDE-PNC) and diethylenetriaminepentaacetic acid (DTPA) dianhydride at varied molar ratios. Then, Gd-chelated CPUAs (denoted as GdCPUAs) were produced by chelating Gd(III) ions with DTPA residues of CPUAs. These GdCPUAs could condense gene into nanosized and positively-charged polyplexes in a physiological condition and, however, liberated gene in an intracellular reductive environment. In vitro transfection experiments revealed that the GdCPUA at a DTDE-PNC/DTPA residue molar ratio of 85/15 induced the highest transfection efficiency in different cancer cells. This efficiency was higher than that yielded with 25kDa branched polyethylenimine as a positive control. GdCPUAs and their polyplexes exhibited low cytotoxicity when an optimal transfection activity was detected. Moreover, GdCPUAs may serve as contrast agents for T1-weighted magnetic resonance imaging. The results of this work indicate that biodegradable Gd-chelated cationic poly(urethane amide) copolymers have high potential for tumor theranostics. PMID:27157741

  2. Highly aromatic polyurea/urethane membranes and their use for the separation of aromatics from non-aromatics

    SciTech Connect

    Schucker, R.C.

    1990-04-03

    This patent describes a dense non-porous polyurea/urethane membrane. It is characterized by possessing a urea index of at least bout 20% but less than 100%, an aromatic carbon content of at least about 15 mole percent, a functional group density of at least about 10 per 1000 grams of polymer and a C{double bond}O/NH ratio of less than about 8.

  3. Cell adhesion force microscopy

    PubMed Central

    Sagvolden, G.; Giaever, I.; Pettersen, E. O.; Feder, J.

    1999-01-01

    The adhesion forces of cervical carcinoma cells in tissue culture were measured by using the manipulation force microscope, a novel atomic force microscope. The forces were studied as a function of time and temperature for cells cultured on hydrophilic and hydrophobic polystyrene substrates with preadsorbed proteins. The cells attached faster and stronger at 37°C than at 23°C and better on hydrophilic than on hydrophobic substrates, even though proteins adsorb much better to the hydrophobic substrates. Because cell adhesion serves to control several stages in the cell cycle, we anticipate that the manipulation force microscope can help clarify some cell-adhesion related issues. PMID:9892657

  4. Adhesive Contact Sweeper

    NASA Technical Reports Server (NTRS)

    Patterson, Jonathan D.

    1993-01-01

    Adhesive contact sweeper removes hair and particles vacuum cleaner leaves behind, without stirring up dust. Also cleans loose rugs. Sweeper holds commercially available spools of inverted adhesive tape. Suitable for use in environments in which air kept free of dust; optics laboratories, computer rooms, and areas inhabited by people allergic to dust. For carpets, best used in tandem with vacuum cleaner; first pass with vacuum cleaner removes coarse particles, and second pass with sweeper extracts fine particles. This practice extends useful life of adhesive spools.

  5. Focal adhesions in osteoneogenesis

    PubMed Central

    Biggs, M.J.P; Dalby, M.J

    2010-01-01

    As materials technology and the field of tissue engineering advances, the role of cellular adhesive mechanisms, in particular the interactions with implantable devices, becomes more relevant in both research and clinical practice. A key tenet of medical device technology is to use the exquisite ability of biological systems to respond to the material surface or chemical stimuli in order to help develop next-generation biomaterials. The focus of this review is on recent studies and developments concerning focal adhesion formation in osteoneogenesis, with an emphasis on the influence of synthetic constructs on integrin mediated cellular adhesion and function. PMID:21287830

  6. Global Functional Connectivity Differences between Sleep-Like States in Urethane Anesthetized Rats Measured by fMRI

    PubMed Central

    Paasonen, Jaakko; Shatillo, Artem; Lipponen, Arto; Salo, Raimo; Aliev, Rubin; Tanila, Heikki; Gröhn, Olli

    2016-01-01

    Sleep is essential for nervous system functioning and sleep disorders are associated with several neurodegenerative diseases. However, the macroscale connectivity changes in brain networking during different sleep states are poorly understood. One of the hindering factors is the difficulty to combine functional connectivity investigation methods with spontaneously sleeping animals, which prevents the use of numerous preclinical animal models. Recent studies, however, have implicated that urethane anesthesia can uniquely induce different sleep-like brain states, resembling rapid eye movement (REM) and non-REM (NREM) sleep, in rodents. Therefore, the aim of this study was to assess changes in global connectivity and topology between sleep-like states in urethane anesthetized rats, using blood oxygenation level dependent (BOLD) functional magnetic resonance imaging. We detected significant changes in corticocortical (increased in NREM-like state) and corticothalamic connectivity (increased in REM-like state). Additionally, in graph analysis the modularity, the measure of functional integration in the brain, was higher in NREM-like state than in REM-like state, indicating a decrease in arousal level, as in normal sleep. The fMRI findings were supported by the supplementary electrophysiological measurements. Taken together, our results show that macroscale functional connectivity changes between sleep states can be detected robustly with resting-state fMRI in urethane anesthetized rats. Our findings pave the way for studies in animal models of neurodegenerative diseases where sleep abnormalities are often one of the first markers for the disorder development. PMID:27168145

  7. A new strategy based on electrospray technique to prepare dual-responsive poly(ether urethane) nanogels.

    PubMed

    Chen, Jiaming; Dai, Huafeng; Lin, Hui; Tu, Kehua; Wang, Hongjun; Wang, Li-Qun

    2016-05-01

    In this work, we proposed a new strategy based on electrospray technique to prepare nanogels. Compared with other methods of preparing nanogels, electrospray technique is more simple and efficient. A biodegradable and multi-responsive poly(ether urethane) (PEU) was synthesized via a facile one-pot method and used as the electrospray material. By using electrospray technique, pH- and redox-responsive poly(ether urethane) nanogels were prepared. The morphologies of the electrospray nanoparticles before and after swelling were demonstrated to be spherical and uniform, as characterized by scanning electron microscope (SEM) and transmission electron microscopy (TEM). Dynamic light scattering (DLS) results showed that the mean hydrodynamic diameter of nanogels was about 500nm. The pH- and redox-sensitive behaviors of nanogels were studied with DLS and TEM. In acidic media the nanogels dissociated, while in the presence of GSH the nanogels degraded. The nanogels suspension was stored at 4°C and was stable without aggregation for at least 30 days. Doxorubicin (DOX) can be further loaded into the poly(ether urethane) nanogels. The electrospray nanogels can change the release rate of loaded drug in response to pH and GSH stimuli. PMID:26859119

  8. Intraperitoneal co-administration of low dose urethane with xylazine and ketamine for extended duration of surgical anesthesia in rats

    PubMed Central

    Clover, Anthony J. P.

    2015-01-01

    Procedures involving complex surgical techniques in rats, such as placement of abdominal aortic graft require extended duration of surgical anesthesia, which often can be achieved by repeated administrations of xylazine-ketamine combination. However such repeated anesthetic administration, in addition to being technically challenging, may be associated with potential adverse events due to cumulative effects of anesthesia. We report here the feasibility of using urethane at low dose (~1/10 the recommended anesthetic dose) in combination with a xylazine-ketamine mix to achieve an extended duration of surgical anesthesia in rats. The anesthesia induction phase was quick and smooth with an optimal phase of surgical anesthesia achieved for up to 90 minutes, which was significantly higher compared to that achieved with use of only xylazine-ketamine combination. The rectal temperature, heart rate and respiratory rate were within the physiological range with an uneventful recovery phase. Post surgery the rats were followed up to 3 months without any evidence of tumor or any other adverse effects related to the use of the urethane anesthetic combination. We conclude that low dose urethane can be effectively used in combination with xylazine and ketamine to achieve extended duration of surgical anesthesia up to 90 minutes in rats. PMID:26755920

  9. Adhesion of Lunar Dust

    NASA Astrophysics Data System (ADS)

    Walton, Otis R.

    2007-04-01

    This paper reviews the physical characteristics of lunar dust and the effects of various fundamental forces acting on dust particles on surfaces in a lunar environment. There are transport forces and adhesion forces after contact. Mechanical forces (i.e., from rover wheels, astronaut boots and rocket engine blast) and static electric effects (from UV photo-ionization and/or tribo-electric charging) are likely to be the major contributors to the transport of dust particles. If fine regolith particles are deposited on a surface, then surface energy-related (e.g., van der Walls) adhesion forces and static-electric-image forces are likely to be the strongest contributors to adhesion. Some measurement techniques are offered to quantify the strength of adhesion forces. And finally some dust removal techniques are discussed.

  10. Adhesion of Lunar Dust

    NASA Technical Reports Server (NTRS)

    Walton, Otis R.

    2007-01-01

    This paper reviews the physical characteristics of lunar dust and the effects of various fundamental forces acting on dust particles on surfaces in a lunar environment. There are transport forces and adhesion forces after contact. Mechanical forces (i.e., from rover wheels, astronaut boots and rocket engine blast) and static electric effects (from UV photo-ionization and/or tribo-electric charging) are likely to be the major contributors to the transport of dust particles. If fine regolith particles are deposited on a surface, then surface energy-related (e.g., van der Walls) adhesion forces and static-electric-image forces are likely to be the strongest contributors to adhesion. Some measurement techniques are offered to quantify the strength of adhesion forces. And finally some dust removal techniques are discussed.

  11. Optical adhesive property study

    SciTech Connect

    Sundvold, P.D.

    1996-01-01

    Tests were performed to characterize the mechanical and thermal properties of selected optical adhesives to identify the most likely candidate which could survive the operating environment of the Direct Optical Initiation (DOI) program. The DOI system consists of a high power laser and an optical module used to split the beam into a number of channels to initiate the system. The DOI requirements are for a high shock environment which current military optical systems do not operate. Five candidate adhesives were selected and evaluated using standardized test methods to determine the adhesives` physical properties. EC2216, manufactured by 3M, was selected as the baseline candidate adhesive based on the test results of the physical properties.

  12. Adhesives for Aerospace

    NASA Technical Reports Server (NTRS)

    Meade, L. E.

    1985-01-01

    The industry is hereby challenged to integrate adhesive technology with the total structure requirements in light of today's drive into automation/mechanization. The state of the art of adhesive technology is fairly well meeting the needs of the structural designers, the processing engineer, and the inspector, each on an individual basis. The total integration of these needs into the factory of the future is the next collective hurdle to be achieved. Improved processing parameters to fit the needs of automation/mechanization will necessitate some changes in the adhesive forms, formulations, and chemistries. Adhesives have, for the most part, kept up with the needs of the aerospace industry, normally leading the rest of the industry in developments. The wants of the aerospace industry still present a challenge to encompass all elements, achieving a totally integrated joined and sealed structural system. Better toughness with hot-wet strength improvements is desired. Lower cure temperatures, longer out times, and improved corrosion inhibition are desired.

  13. Leucocyte cellular adhesion molecules.

    PubMed

    Yong, K; Khwaja, A

    1990-12-01

    Leucocytes express adhesion promoting receptors which mediate cell-cell and cell-matrix interactions. These adhesive interactions are crucial to the regulation of haemopoiesis and thymocyte maturation, the direction and control of leucocyte traffic and migration through tissues, and in the development of immune and non-immune inflammatory responses. Several families of adhesion receptors have been identified (Table). The leucocyte integrin family comprises 3 alpha beta heterodimeric membrane glycoproteins which share a common beta subunit, designated CD18. The alpha subunits of each of the 3 members, lymphocyte function associated antigen-1 (LFA-1), macrophage antigen-1 (Mac-1) and p150,95 are designated CD11a, b and c respectively. These adhesion molecules play a critical part in the immune and inflammatory responses of leucocytes. The leucocyte integrin family is, in turn, part of the integrin superfamily, members of which are evolutionally, structurally and functionally related. Another Integrin subfamily found on leucocytes is the VLA group, so-called because the 'very late activation antigens' VLA-1 and VLA-2 were originally found to appear late in T-cell activation. Members of this family function mainly as extracellular matrix adhesion receptors and are found both on haemopoietic and non-haemopoietic cells. They play a part in diverse cellular functions including tissue organisation, lymphocyte recirculation and T-cell immune responses. A third integrin subfamily, the cytoadhesins, are receptors on platelets and endothelial cells which bind extracellular matrix proteins. A second family of adhesion receptors is the immunoglobulin superfamily, members of which include CD2, LFA-3 and ICAM-1, which participate in T-cell adhesive interactions, and the antigen-specific receptors of T and B cells, CD4, CD8 and the MHC Class I and II molecules. A recently recognised family of adhesion receptors is the selectins, characterised by a common lectin domain. Leucocyte

  14. 45 CFR 88.3 - Applicability.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... DEPARTMENT OF HEALTH AND HUMAN SERVICES GENERAL ADMINISTRATION ENSURING THAT DEPARTMENT OF HEALTH AND HUMAN...) The Department of Health and Human Services is required to comply with sections §§ 88.4(a), (b)(1... through the appropriations act for the Department of Health and Human Services is required to comply...

  15. 32 CFR 88.3 - Definitions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Service shall be considered to be involuntarily separated if he or she was on active duty or full-time... officer who is on the active duty list or, if not on the active duty list, is on full-time active duty (or... involuntarily discharged or released from active duty or full-time National Guard duty (other than a...

  16. High temperature adhesives

    NASA Technical Reports Server (NTRS)

    St.clair, Terry L.

    1991-01-01

    The aerospace and electronics industries have an ever increasing need for higher performance materials. In recent years, linear aromatic polyimides have been proven to be a superior class of materials for various applications in these industries. The use of this class of polymers as adhesives is continuing to increase. Several NASA Langley developed polyimides show considerable promise as adhesives because of their high glass transition temperatures, thermal stability, resistance to solvents/water, and their potential for cost effective manufacture.

  17. Microencapsulation of maltogenic α-amylase in poly(urethane-urea) shell: inverse emulsion method.

    PubMed

    Maciulyte, Sandra; Kochane, Tatjana; Budriene, Saulute

    2015-01-01

    The novel poly(urethane-urea) microcapsules (PUUMC) were obtained by the interfacial polyaddition reaction between the oil-soluble hexamethylene diisocyanate (HMDI) and the water soluble poly(vinyl alcohol) (PVA) in a water-in-oil (W/O) emulsion. The PVA was used instead of diols. Maltogenase L (maltogenic α-amylase from Bacillus stearothermophilus (E. C. 3.2.1.133) (MG) was encapsulated in the PUUMC during or after formation of capsules. The PUUMC were thoroughly characterised by chemical analytical methods, FT-IR, SEM, thermal analysis, surface area, pore volume and size analysis. Furthermore, by carefully analysing the influencing factors including: catalyst and surfactants and their concentrations, the initial molar ratio of PVA and HMDI, stirring rate and ratio of dispersed phase to external phase, the optimum synthesis conditions were found out. A controlled release of MG could be observed in many cases. Delayed-release capsules were obtained when initial concentration of HMDI was increased. These capsules have potential application in biotechnology for saccharification of starch. PMID:26190216

  18. Fabrication and characterization of biomimetic multichanneled crosslinked-urethane doped polyester (CUPE) tissue engineered nerve guides

    PubMed Central

    Tran, Richard. T.; Choy, Wai Man; Cao, Hung; Qattan, Ibrahim; Chiao, Jung-Chih; Ip, Wing Yuk; Yeung, Kelvin Wai Kwok; Yang, Jian

    2013-01-01

    Biomimetic scaffolds that replicate the native architecture and mechanical properties of target tissues have been recently shown to be a very promising strategy to guide cellular growth and facilitate tissue regeneration. In this study, porous, soft, and elastic crosslinked urethane-doped polyester (CUPE) tissue engineered nerve guides were fabricated with multiple longitudinally oriented channels and an external non-porous sheath to mimic the native endoneurial microtubular and epineurium structure, respectively. The fabrication technique described herein is highly adaptable and allows for fine control over the resulting nerve guide architecture in terms of channel number, channel diameter, porosity, and mechanical properties. Biomimetic multichanneled CUPE guides were fabricated with various channel numbers and displayed an ultimate peak stress of 1.38 ± 0.22 MPa with a corresponding elongation at break of 122.76 ± 42.17 %, which were comparable to that of native nerve tissue. The CUPE nerve guides were also evaluated in vivo for the repair of a 1 cm rat sciatic nerve defect. Although histological evaluations revealed collapse of the inner structure from CUPE TENGs, the CUPE nerve guides displayed fiber populations and densities comparable with nerve autograft controls after 8 weeks of implantation. These studies are the first report of a CUPE-based biomimetic multichanneled nerve guide and warrant future studies towards optimization of the channel geometry for use in neural tissue engineering. PMID:24115502

  19. Synthesis of polyester urethane urea and fabrication of elastomeric nanofibrous scaffolds for myocardial regeneration.

    PubMed

    Jamadi, Elham Sadat; Ghasemi-Mobarakeh, Laleh; Morshed, Mohammad; Sadeghi, Morteza; Prabhakaran, Molamma P; Ramakrishna, Seeram

    2016-06-01

    Fabrication of bioactive scaffolds is one of the most promising strategies to reconstruct the infarcted myocardium. In this study, we synthesized polyester urethane urea (PEUU), further blended it with gelatin and fabricated PEUU/G nanofibrous scaffolds. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), differential scanning calorimetry (DSC) and X-ray diffraction were used for the characterization of the synthesized PEUU and properties of nanofibrous scaffolds were evaluated using scanning electron microscopy (SEM), ATR-FTIR, contact angle measurement, biodegradation test, tensile strength analysis and dynamic mechanical analysis (DMA). In vitro biocompatibility studies were performed using cardiomyocytes. DMA analysis showed that the scaffolds could be reshaped with cyclic deformations and might remain stable in the frequencies of the physiological activity of the heart. On the whole, our study suggests that aligned PEUU/G 70:30 nanofibrous scaffolds meet the required specifications for cardiac tissue engineering and could be used as a promising construct for myocardial regeneration. PMID:27040201

  20. Amorphous calcium phosphate/urethane methacrylate resin composites. I. Physicochemical characterization

    PubMed Central

    Regnault, W.F.; Icenogle, T.B.; Antonucci, J.M.; Skrtic, D.

    2008-01-01

    Urethane dimethacrylate (UDMA), an oligomeric poly(ethylene glycol) extended UDMA (PEG-U) and a blend of UDMA/PEG-U were chosen as model systems for introducing both hydrophobic and hydrophilic segments and a range of compliances in their derived polymers. Experimental composites based on these three resins with amorphous calcium phosphate (ACP) as the filler phase were polymerized and evaluated for mechanical strength and ion release profiles in different aqueous media. Strength of all composites decreased upon immersion in saline (pH = 7.4). Both polymer matrix composition and the pH of the liquid environment strongly affected the ion release kinetics. In saline, the UDMA/PEG-U composite showed a sustained release for at least 350 h. The initially high ion release of the PEG-U composites decreased after 72 h, seemingly due to the mineral re-deposition at the composite surface. Internal conversion from ACP to poorly crystallized apatite could be observed by X-ray diffraction. In various lactic acid (LA) environments (initial pH = 5.1) ion release kinetics was much more complex. In LA medium without thymol and/or carboxymethylcellulose, as a result of unfavorable changes in the internal calcium/phosphate ion stoichiometry, the ion release rate greatly increased but without observable conversion of ACP to apatite. PMID:17619969

  1. Structure-property relationships of an electron beam cured model urethane prepolymer

    SciTech Connect

    Joseph, E.; Wilkes, G.; Park, K.

    1981-10-01

    A semicrystalline urethane prepolymer derived from polycaprolactone was crosslinked below and above the melt to different levels using electron beam radiation. Studies at room temperature on the systems crosslinked under ambient conditions, which is below the melting temperature, show that changes in mechanical properties which occur as the electron beam dose is increased are due principally to the increase in crosslink density and to the changes in the crosslinking mechanism. Specifically, crosslinking takes place mainly at the acrylate double bonds or may also occur along the polymer backbone. All systems, however, are semicrystalline and possess a spherulitic texture. Mechanical and rheo-optical testing above the melt on these same systems indicate that at extensions up to 125% classical rubber elasticity theory and photoelasticity theory is obeyed. Isothermal crystallization kinetics measurements show that the rate of crystallization decreases as the electron beam dose is raised. When the systems are crosslinked above the melt again a spherulitic texture results. Mechanical testing above the melting temperature on the prepolymer crosslinked up to 4 Mrad shows that at elongations up to 125% classical rubber elasticity theory is obeyed. At room temperature these latter crosslinked systems exhibited a lower modulus compared to the materials crosslinked below the melt. Polarizing optical microscopy carried out above the melting temperature strongly suggested that no order was present in these systems during crosslinking in contrast to those crosslinked below the melting temperature.

  2. Ultraviolet photoelectron spectroscopy study of the thermochromic phase transition in urethane-substituted polydiacetylenes

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoyu; Whitten, James E.; Sandman, Daniel J.

    2007-05-01

    Threshold solid-state ionization energies determined from ultraviolet photoelectron spectra are reported for the thermochromic polydiacetylenes (PDAs) from the bis-ethyl- and bis-n-propyl urethanes of 5,7-dodecadiyn-1,12-diol (ETCD and PUDO, respectively) and the nonthermochromic 1,6-bis-p-toluenesulfonate of 2,4-hexadiyne-1,6-diol (PTS) at temperatures above and below the thermochromic phase transition. PDA-PTS has an ionization energy of 5.66eV which does not change significantly as the temperature is raised above 140°C. At 25°C, PDA-ETCD and PDA-PUDO have threshold ionization energies of 5.65 and 5.51eV, respectively. The ionization energies of these PDAs increase by approximately 0.34eV as temperature is raised above 140°C and returns to the lower values as temperature is reduced to 25°C. The magnitude of the increase in ionization energy on heating to temperatures above the thermochromic transition is very close to the shift in energy of the electronic spectrum over the same temperature range. These observations suggest that the structural changes that take place in the course of the thermochromic transition are primarily associated with the valence band and are consistent with partial relief of mechanical strains.

  3. Use of iron monocarboxylates in the two-step preparation of poly(ester-urethane)s.

    PubMed

    Stolt, M; Hiltunen, K; Södergård, A

    2001-01-01

    Five different iron monocarboxylates were used as catalysts in the two-step preparation route of lactic acid based poly(ester-urethane)s (PEU). In the first step, a hydroxyl-terminated poly(lactic acid) prepolymer was prepared, which in the second step was linked with 1,6-hexamethylene diisocyanate. The resulting polymers were characterized by titration, size exclusion chromatography, differential scanning calorimetry, and nuclear magnetic resonance spectroscopy, and the mechanical properties were tested as well. Iron monocarboxylates proved to be efficient catalysts in the preparation of a hydroxyl-terminated prepolymer (lowest acid number obtained: 0.08). The same catalyst systems proved also to be highly efficient in the linking step yielding a high molar mass PEU. Semicrystalline PEUs could be prepared at 160 and 180 degrees C by using the iron acetate of different oxidation state. PEU prepared at 200 degrees C was amorphous, which could be related to racemization during the polycondensation. By using the fluorinated iron acetate amorphous PEUs was prepared at all reaction temperatures. The molar mass of the prepolymers and the PEUs increased as a function of the polycondensation temperature for all catalysts used. The highest weight-average molar masses (M(w)) were obtained by using the fluorinated iron acetate. PMID:11777398

  4. A novel candidate compound with urethane structure for anticancer drug development.

    PubMed

    Matsuoka, Atsuko; Isama, Kazuo; Tanimura, Susumu; Kohno, Michiaki; Yamori, Takao

    2007-08-01

    Diethyl-4,4'-methylenebis(N-phenylcarbamate) (MDU) is a urethane compound that we originally synthesized, along with three other compounds, to investigate how polyurethane is hydrolysed. We tested the four compounds for cytotoxicity in two Chinese hamster cell lines (CHL and V79) and a human cancer cell line (HeLa S3). MDU showed the strongest cytotoxicity in all the cell lines with an IC50 of around 0.1 microg/ml. We further investigated MDU for its ability to induce chromosome aberrations (CAs) and micronuclei (MN) in CHL cells. MDU induced around 100% polyploid cells at 0.5 microg/ml after 24- and 48-h treatment in the CA test and a significantly increased frequency of micronuclei, polynuclear cells, and mitotic cells in the MN test, suggesting that it may induce numerical CAs. MDU's ability to cause mitotic arrest in CHL cells was greater than that of taxol and colchicine. Based on a COMPARE analysis using JFCR39, a panel of cancer cell lines, we predicted MDU to be a tubulin inhibitor. We confirmed this possibility in nerve growth factor-stimulated PC12 cells as well as in HT1080 cells, in which MDU exhibited the activity to inhibit tubulin polymerization. MDU is simpler in structure than existing anticancer drugs taxol and vincristine and can be synthesized relatively easily. Here we offer MDU as a potential new type of anticancer drug, stable even at room temperature, and inexpensive. PMID:17691911

  5. Synthesis and characterization of polycaprolactone urethane hollow fiber membranes as small diameter vascular grafts.

    PubMed

    Mercado-Pagán, Ángel E; Stahl, Alexander M; Ramseier, Michelle L; Behn, Anthony W; Yang, Yunzhi

    2016-07-01

    The design of bioresorbable synthetic small diameter (<6mm) vascular grafts (SDVGs) capable of sustaining long-term patency and endothelialization is a daunting challenge in vascular tissue engineering. Here, we synthesized a family of biocompatible and biodegradable polycaprolactone (PCL) urethane macromers to fabricate hollow fiber membranes (HFMs) as SDVG candidates, and characterized their mechanical properties, degradability, hemocompatibility, and endothelial development. The HFMs had smooth surfaces and porous internal structures. Their tensile stiffness ranged from 0.09 to 0.11N/mm and their maximum tensile force from 0.86 to 1.03N, with minimum failure strains of approximately 130%. Permeability varied from 1 to 14×10(-6)cm/s, burst pressures from 1158 to 1468mmHg, and compliance from 0.52 to 1.48%/100mmHg. The suture retention forces ranged from 0.55 to 0.81N. HFMs had slow degradation profiles, with 15 to 30% degradation after 8weeks. Human endothelial cells proliferated well on the HFMs, creating stable cell layer coverage. Hemocompatibility studies demonstrated low hemolysis (<2%), platelet activation, and protein adsorption. There were no significant differences in the hemocompatibility of HFMs in the absence and presence of endothelial layers. These encouraging results suggest great promise of our newly developed materials and biodegradable elastomeric HFMs as SDVG candidates. PMID:27127029

  6. Using Chain Extenders to Modify Release Rates of Orange Oil from Poly(Urea-Urethane) Microcapsules.

    PubMed

    Pušlar, Jurij; Štefanec, Dejan; Vrhunec, Aljoša

    2015-01-01

    Poly(urea-urethane) and polyurea microcapsules were prepared by an interfacial polymerisation using orange oil as a core material and a mixture of polymeric 4,4'-methylene diphenyl diisocyanate and toluene diisocyanate in a molar ratio of 1:0.2 as oil-soluble monomers. The membrane composition, thickness, and other properties were varied by changing the type and amount of oil-soluble monomers and water-soluble chain extenders, such as ethylenediamine and diethylenetriamine based on amine groups and 1,4-butanediol and polyethylene glycol 400 based on hydroxyl groups. Studies of the morphology and release behaviour show high dependency on the reaction conditions and reactants' properties. The release rate of the orange oil from microcapsules is highest when using a polymeric linear chain extender, polyethylene glycol with a molecular mass of 400. Microcapsules with improved mechanical stability and a slower release rate were obtained by a thicker membrane and by using the branched multi-functional chain extender diethylenetriamine. PMID:26454605

  7. The mechanisms of cytotoxicity of urethane dimethacrylate to Chinese hamster ovary cells.

    PubMed

    Chang, Hsiao-Hua; Chang, Mei-Chi; Lin, Li-Deh; Lee, Jang-Jaer; Wang, Tong-Mei; Huang, Chun-Hsun; Yang, Ting-Ting; Lin, Hsueh-Jen; Jeng, Jiiang-Huei

    2010-09-01

    Monomers released from resin-containing products may cause various adverse effects. Urethane dimethacrylate (UDMA) is a principal resin monomer and also a major component released from various dental resin materials. Thus the toxic effects and mechanisms should be elucidated for improving of its safety use. Here we investigated the effects of UDMA on the growth, cell cycle progression, reactive oxygen species (ROS) production and glutathione (GSH) alteration in CHO-K1 cells, and the preventive effects by antioxidants (NAC and catalase) were also evaluated. UDMA elicited growth inhibition (>0.025 mm) of CHO-K1 cells in a clearly dose-dependent manner. Cell cycle perturbation and ROS overproduction were also observed. A 0.1 mm UDMA-induced S-phase cell cycle arrest and ROS accumulation. Cell apoptosis and necrosis became significant when UDMA concentration was 0.25 mm. GSH depletion occurred at cells treated with 0.25 mm UDMA, a highly cytotoxic concentration at which point myriad cells were under apoptosis or necrosis. Thus GSH depletion can be crucial for the death of CHO-K1 cells. Furthermore NAC (0.5-10 mm) and catalase (250-1000 U/ml) obviously attenuated the UDMA-induced toxicity by reducing ROS generation and cell cycle disturbance, and the effects were dose-related. These results suggest that UDMA toxicity is associated with ROS production, GSH depletion, cell cycle disturbance and cell apoptosis/necrosis. PMID:20579731

  8. Poly(ester-urethane) scaffolds: effect of structure on properties and osteogenic activity of stem cells.

    PubMed

    Kiziltay, Aysel; Marcos-Fernandez, Angel; San Roman, Julio; Sousa, Rui A; Reis, Rui L; Hasirci, Vasif; Hasirci, Nesrin

    2015-08-01

    The present study aimed to investigate the effect of structure (design and porosity) on the matrix stiffness and osteogenic activity of stem cells cultured on poly(ester-urethane) (PEU) scaffolds. Different three-dimensional (3D) forms of scaffold were prepared from lysine-based PEU using traditional salt-leaching and advanced bioplotting techniques. The resulting scaffolds were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), mercury porosimetry and mechanical testing. The scaffolds had various pore sizes with different designs, and all were thermally stable up to 300 °C. In vitro tests, carried out using rat bone marrow stem cells (BMSCs) for bone tissue engineering, demonstrated better viability and higher cell proliferation on bioplotted scaffolds compared to salt-leached ones, most probably due to their larger and interconnected pores and stiffer nature, as shown by higher compressive moduli, which were measured by compression testing. Similarly, SEM, von Kossa staining and EDX analyses indicated higher amounts of calcium deposition on bioplotted scaffolds during cell culture. It was concluded that the design with larger interconnected porosity and stiffness has an effect on the osteogenic activity of the stem cells. PMID:24376070

  9. In-vivo degradation of poly(carbonate-urethane) based spine implants

    PubMed Central

    Cipriani, E.; Bracco, P.; Kurtz, S.M.; Costa, L.; Zanetti, M.

    2013-01-01

    Fourteen explanted Dynesys® spinal devices were analyzed for biostability and compared with a reference, never implanted, control. Both poly(carbonate-urethane) (PCU) spacers and polyethylene-terephthalate (PET) cords were analyzed. The effect of implantation was evaluated through the observation of physical alterations of the device surfaces, evaluation of the chemical degradation and fluids absorption on the devices and examination of the morphological and mechanical features. PCU spacers exhibited a variety of surface damage mechanisms, the most significant being abrasion and localized, microscopic surface cracks. Evidence of oxidation and chain scission were detected on PCU spacers ATR–FTIR. ATR–FTIR, DSC and hardness measurements also showed a slight heterogeneity in the composition of PCU. The extraction carried out on the PCU spacers revealed the presence of extractable polycarbonate segments. One spacer and all PET cords visually exhibited the presence of adherent biological material (proteins), confirmed by the ATR–FTIR results. GC/MS analyses of the extracts from PET cords revealed the presence of biological fluids residues, mainly cholesterol derivatives and fatty acids, probably trapped into the fiber network. No further chemical alterations were observed on the PET cords. Although the observed physical and chemical damage can be considered superficial, greater attention must be paid to the chemical degradation mechanisms of PCU and to the effect of byproducts on the body. PMID:24043907

  10. Epithelial Cell Adhesion Molecule

    PubMed Central

    Trzpis, Monika; McLaughlin, Pamela M.J.; de Leij, Lou M.F.H.; Harmsen, Martin C.

    2007-01-01

    The epithelial cell adhesion molecule (EpCAM, CD326) is a glycoprotein of ∼40 kd that was originally identified as a marker for carcinoma, attributable to its high expression on rapidly proliferating tumors of epithelial origin. Normal epithelia express EpCAM at a variable but generally lower level than carcinoma cells. In early studies, EpCAM was proposed to be a cell-cell adhesion molecule. However, recent insights revealed a more versatile role for EpCAM that is not limited only to cell adhesion but includes diverse processes such as signaling, cell migration, proliferation, and differentiation. Cell surface expression of EpCAM may actually prevent cell-cell adhesion. Here, we provide a comprehensive review of the current knowledge on EpCAM biology in relation to other cell adhesion molecules. We discuss the implications of the newly identified functions of EpCAM in view of its prognostic relevance in carcinoma, inflammatory pathophysiology, and tissue development and regeneration as well as its role in normal epithelial homeostasis. PMID:17600130

  11. Flexibilized copolyimide adhesives

    NASA Technical Reports Server (NTRS)

    Progar, Donald J.; St.clair, Terry L.

    1988-01-01

    Two copolyimides, LARC-STPI and STPI-LARC-2, with flexible backbones were processed and characterized as adhesives. The processability and adhesive properties were compared to those of a commercially available form of LARC-TPI. Lap shear specimens were fabricated using adhesive tape prepared from each of the three polymers. Lap shear tests were performed at room temperature, 177 C, and 204 C before and after exposure to water-boil and to thermal aging at 204 C for up to 1000 hours. The three adhesive systems possess exceptional lap shear strengths at room temperature and elevated temperatures both before and after thermal exposure. LARC-STPI, because of its high glass transition temperature provided high lap shear strengths up to 260 C. After water-boil, LARC-TPI exhibited the highest lap shear strengths at room temperature and 177 C, whereas the LARC-STPI retained a higher percentage of its original strength when tested at 204 C. These flexible thermoplastic copolyimides show considerable potential as adhesives based on this study and because of the ease of preparation with low cost, commercially available materials.

  12. Platelet Adhesion under Flow

    PubMed Central

    Ruggeri, Zaverio M.

    2011-01-01

    Platelet adhesive mechanisms play a well-defined role in hemostasis and thrombosis, but evidence continues to emerge for a relevant contribution to other pathophysiological processes including inflammation, immune-mediated responses to microbial and viral pathogens, and cancer metastasis. Hemostasis and thrombosis are related aspects of the response to vascular injury, but the former protects from bleeding after trauma while the latter is a disease mechanism. In either situation, adhesive interactions mediated by specific membrane receptors support the initial attachment of single platelets to cellular and extracellular matrix constituents of the vessel wall and tissues. In the subsequent steps of thrombus growth and stabilization, adhesive interactions mediate platelet to platelet cohesion (aggregation) and anchoring to the fibrin clot. A key functional aspect of platelets is their ability to circulate in a quiescent state surveying the integrity of the inner vascular surface, coupled to a prompt reaction wherever alterations are detected. In many respects, therefore, platelet adhesion to vascular wall structures, to one another or to other blood cells are facets of the same fundamental biological process. The adaptation of platelet adhesive functions to the effects of blood flow is the main focus of this review. PMID:19191170

  13. Protein mediated membrane adhesion

    NASA Astrophysics Data System (ADS)

    Carlson, Andreas; Mahadevan, L.

    2015-05-01

    Adhesion in the context of mechanical attachment, signaling, and movement in cellular dynamics is mediated by the kinetic interactions between membrane-embedded proteins in an aqueous environment. Here, we present a minimal theoretical framework for the dynamics of membrane adhesion that accounts for the kinetics of protein binding, the elastic deformation of the membrane, and the hydrodynamics of squeeze flow in the membrane gap. We analyze the resulting equations using scaling estimates to characterize the spatiotemporal features of the adhesive patterning and corroborate them using numerical simulations. In addition to characterizing aspects of cellular dynamics, our results might also be applicable to a range of phenomena in physical chemistry and materials science where flow, deformation, and kinetics are coupled to each other in slender geometries.

  14. Adhesive particle shielding

    DOEpatents

    Klebanoff, Leonard Elliott; Rader, Daniel John; Walton, Christopher; Folta, James

    2009-01-06

    An efficient device for capturing fast moving particles has an adhesive particle shield that includes (i) a mounting panel and (ii) a film that is attached to the mounting panel wherein the outer surface of the film has an adhesive coating disposed thereon to capture particles contacting the outer surface. The shield can be employed to maintain a substantially particle free environment such as in photolithographic systems having critical surfaces, such as wafers, masks, and optics and in the tools used to make these components, that are sensitive to particle contamination. The shield can be portable to be positioned in hard-to-reach areas of a photolithography machine. The adhesive particle shield can incorporate cooling means to attract particles via the thermophoresis effect.

  15. Natural Underwater Adhesives

    PubMed Central

    Stewart, Russell J.; Ransom, Todd C.; Hlady, Vladimir

    2011-01-01

    The general topic of this review is protein-based underwater adhesives produced by aquatic organisms. The focus is on mechanisms of interfacial adhesion to native surfaces and controlled underwater solidification of natural water-borne adhesives. Four genera that exemplify the broad range of function, general mechanistic features, and unique adaptations are discussed in detail: blue mussels, acorn barnacles, sandcastle worms, and freshwater caddisfly larva. Aquatic surfaces in nature are charged and in equilibrium with their environment, populated by an electrical double layer of ions as well as adsorbed natural polyelectrolytes and microbial biofilms. Surface adsorption of underwater bioadhesives likely occurs by exchange of surface bound ligands by amino acid sidechains, driven primarily by relative affinities and effective concentrations of polymeric functional groups. Most aquatic organisms exploit modified amino acid sidechains, in particular phosphorylated serines and hydroxylated tyrosines (dopa), with high-surface affinity that form coordinative surface complexes. After delivery to the surfaces as a fluid, permanent natural adhesives solidify to bear sustained loads. Mussel plaques are assembled in a manner superficially reminiscent of in vitro layer-by-layer strategies, with sequentially delivered layers associated through Fe(dopa)3 coordination bonds. The adhesives of sandcastle worms, caddisfly larva, and barnacles may be delivered in a form somewhat similar to in vitro complex coacervation. Marine adhesives are secreted, or excreted, into seawater that has a significantly higher pH and ionic strength than the internal environment. Empirical evidence suggests these environment triggers could provide minimalistic, fail-safe timing mechanisms to prevent premature solidification (insolubilization) of the glue within the secretory system, yet allow rapid solidification after secretion. Underwater bioadhesives are further strengthened by secondary covalent

  16. Short Term Evaluation of an Anatomically Shaped Polycarbonate Urethane Total Meniscus Replacement in a Goat Model

    PubMed Central

    Vrancken, A. C. T.; Madej, W.; Hannink, G.; Verdonschot, N.; van Tienen, T. G.; Buma, P.

    2015-01-01

    Purpose Since the treatment options for symptomatic total meniscectomy patients are still limited, an anatomically shaped, polycarbonate urethane (PCU), total meniscus replacement was developed. This study evaluates the in vivo performance of the implant in a goat model, with a specific focus on the implant location in the joint, geometrical integrity of the implant and the effect of the implant on synovial membrane and articular cartilage histopathological condition. Methods The right medial meniscus of seven Saanen goats was replaced by the implant. Sham surgery (transection of the MCL, arthrotomy and MCL suturing) was performed in six animals. The contralateral knee joints of both groups served as control groups. After three months follow-up the following aspects of implant performance were evaluated: implant position, implant deformation and the histopathological condition of the synovium and cartilage. Results Implant geometry was well maintained during the three month implantation period. No signs of PCU wear were found and the implant did not induce an inflammatory response in the knee joint. In all animals, implant fixation was compromised due to suture breakage, wear or elongation, likely causing the increase in extrusion observed in the implant group. Both the femoral cartilage and tibial cartilage in direct contact with the implant showed increased damage compared to the sham and sham-control groups. Conclusion This study demonstrates that the novel, anatomically shaped PCU total meniscal replacement is biocompatible and resistant to three months of physiological loading. Failure of the fixation sutures may have increased implant mobility, which probably induced implant extrusion and potentially stimulated cartilage degeneration. Evidently, redesigning the fixation method is necessary. Future animal studies should evaluate the improved fixation method and compare implant performance to current treatment standards, such as allografts. PMID:26192414

  17. Simulation for Dry Spinning Process of Segmented Poly (urethane-urea) Fibers

    NASA Astrophysics Data System (ADS)

    Li, Guangzhu; Yamada, Toshiro; Tada, Kaoru; Katsuo, Ken-Ichi; Ishihara, Hideaki

    Segmented poly (urethane-urea) (SPUU) fibers such as spandex fibers are usually produced by dry spinning process. The processing conditions for dry spinning of SPUU can be optimized by computer simulation. In this work, a simulation model is proposed for the dry spinning process where the SPUU dope in the liquid state is first extruded from the nozzle in the shape of spinline, then the solvent in the spinline is removed by the blowing of hot gas while elongated, and finally a few spinlines come to a fiber in the solid state after they are twisted. The deformation behavior, solvent concentration, temperature of spinline and so on can be predicted with this model. Governing equations composed of the equations of continuity, motion, energy, rheology and deflection were derived under the assumption of Newtonian fluid. Simulations for dry spinning process were carried out with various diffusion coefficients previously reported for two kinds of solvents (dimethyl formamid (DMF), dimethyl acetamide (DMAc)) and three measurement methods of diffusion coefficients (Moiré pattern, Film and Dope methods), where Moiré pattern method gives the mutual diffusion coefficient for the liquid-liquid system, Film method gives the diffusion coefficient of solvent into the film which changes from the solid state to the semisolid state during measurement, and Dope method gives the diffusion coefficient of solvent from the dope which changes from the liquid state to the (semi-) solid state during measurement. The temperature distribution in the spinning chamber was linearly approximated in the distribution close to a practical plant. The simulation model can predict the residual solvent concentration, temperature, cross sectional area, spinning stress and deflection of spinline. The simulation results denoted that the change of solvent concentration is mainly determined in the hot gas zone even if the diffusion coefficients are different. Therefore, the deformation behavior of spinline

  18. Urodynamic function during sleep-like brain states in urethane anesthetized rats

    PubMed Central

    Crook, J.; Lovick, T.

    2016-01-01

    The aim was to investigate urodynamic parameters and functional excitability of the periaqueductal gray matter (PAG) during changes in sleep-like brain states in urethane anesthetized rats. Simultaneous recordings of detrusor pressure, external urethral sphincter (EUS) electromyogram (EMG), cortical electroencephalogram (EEG), and single-unit activity in the PAG were made during repeated voiding induced by continuous infusion of saline into the bladder. The EEG cycled between synchronized, high-amplitude slow wave activity (SWA) and desynchronized low-amplitude fast activity similar to slow wave and ‘activated’ sleep-like brain states. During (SWA, 0.5–1.5 Hz synchronized oscillation of the EEG waveform) voiding became more irregular than in the ‘activated’ brain state (2–5 Hz low-amplitude desynchronized EEG waveform) and detrusor void pressure threshold, void volume threshold and the duration of bursting activity in the external urethral sphincter EMG were raised. The spontaneous firing rate of 23/52 neurons recorded within the caudal PAG and adjacent tegmentum was linked to the EEG state, with the majority of responsive cells (92%) firing more slowly during SWA. Almost a quarter of the cells recorded (12/52) showed phasic changes in firing rate that were linked to the occurrence of voids. Inhibition (n = 6), excitation (n = 4) or excitation/inhibition (n = 2) was seen. The spontaneous firing rate of 83% of the micturition-responsive cells was sensitive to changes in EEG state. In nine of the 12 responsive cells (75%) the responses were reduced during SWA. We propose that during different sleep-like brain states changes in urodynamic properties occur which may be linked to changing excitability of the micturition circuitry in the periaqueductal gray. PMID:26601774

  19. Synthesis and characterisation of coating polyurethane cationomers containing fluorine built-in hard urethane segments.

    PubMed

    Król, Bożena; Król, Piotr; Pikus, Stanisław; Chmielarz, Paweł; Skrzypiec, Krzysztof

    2010-08-01

    Polyurethane cationomers were synthesised in the reaction of 4,4'-methylenebis(phenyl isocyanate) with polyoxyethylene glycol (M = 2,000) or poly(tetrafluoroethyleneoxide-co-difluoromethylene oxide) α,ω-diisocyanate and N-methyl diethanolamine. Amine segments were built-in to the urethane-isocyanate prepolymer in the reaction with 1-bromobutane or formic acid, and then they were converted to alkylammonium cations. The obtained isocyanate prepolymers were then extended in the aqueous medium that yielded stable aqueous dispersions which were applied on the surfaces of test poly(tetrafluoroethylene) plates. After evaporation of water, the dispersions formed thin polymer coatings. (1)H, (13)C NMR and IR spectral methods were employed to confirm chemical structures of synthesised cationomers. Based on (1)H NMR and IR spectra, the factors κ and α were calculated, which represented the polarity level of the obtained cationomers. The DSC, wide angle X-ray scattering and atom force microscopy methods were employed for the microstructural assessment of the obtained materials. Changes were discussed in the surface free energy and its components, as calculated independently according to the method suggested by van Oss-Good, in relation to chemical and physical structures of cationomers as well as morphology of coating surfaces obtained from those cationomers. Fluorine incorporated into cationomers (about 30%) contributed to lower surface free energy values, down to about 15 mJ/m(2). That was caused by gradual weakening of long-range interactions within which the highest share is taken by dispersion interactions. PMID:20927181

  20. Synthesis and characterisation of coating polyurethane cationomers containing fluorine built-in hard urethane segments

    PubMed Central

    Król, Bożena; Pikus, Stanisław; Chmielarz, Paweł; Skrzypiec, Krzysztof

    2010-01-01

    Polyurethane cationomers were synthesised in the reaction of 4,4’-methylenebis(phenyl isocyanate) with polyoxyethylene glycol (M = 2,000) or poly(tetrafluoroethyleneoxide-co-difluoromethylene oxide) α,ω-diisocyanate and N-methyl diethanolamine. Amine segments were built-in to the urethane-isocyanate prepolymer in the reaction with 1-bromobutane or formic acid, and then they were converted to alkylammonium cations. The obtained isocyanate prepolymers were then extended in the aqueous medium that yielded stable aqueous dispersions which were applied on the surfaces of test poly(tetrafluoroethylene) plates. After evaporation of water, the dispersions formed thin polymer coatings. 1H, 13C NMR and IR spectral methods were employed to confirm chemical structures of synthesised cationomers. Based on 1H NMR and IR spectra, the factors κ and α were calculated, which represented the polarity level of the obtained cationomers. The DSC, wide angle X-ray scattering and atom force microscopy methods were employed for the microstructural assessment of the obtained materials. Changes were discussed in the surface free energy and its components, as calculated independently according to the method suggested by van Oss–Good, in relation to chemical and physical structures of cationomers as well as morphology of coating surfaces obtained from those cationomers. Fluorine incorporated into cationomers (about 30%) contributed to lower surface free energy values, down to about 15 mJ/m2. That was caused by gradual weakening of long-range interactions within which the highest share is taken by dispersion interactions. PMID:20927181

  1. The effects of moisture on the dielectric relaxation of urethane dimethacrylate polymer and composites.

    PubMed

    Mohsen, N M; Craig, R G; Filisko, F E

    2001-04-01

    Dielectric characterization evaluated the influence of sorbed moisture on urethane dimethacrylate (UDMA) polymer matrix and unsilanated and silanated zirconia-silica (ZS)-filled UDMA composites. The moisture content (MC) of samples tested ranged from 0 to 7.32% with maximum values for UDMA, silanated and unsilanated ZS-filled UDMA were 3.72, 6.0 and 7.32%, respectively. Dielectric spectra were measured from 0.053 to 100 kHz and from -180 to 180;C. Small MC stiffened the polymers, which was shown by a shift of beta-peaks to higher temperatures, a decrease in the half width of bands and an increase in the change of activation energies. Higher MC resulted in water plasticizing the polymer by shifting the beta-peaks to lower temperatures. Maximum water sorption restricted the motion of the polymer chains and the b-peaks shifted to higher temperatures. Further, increasing MC shifted the a-relaxation to lower temperatures in both UDMA and composites. However, in composites with unsilanated ZS, a new relaxation occurred at high temperatures and low frequencies which was attributed to Maxwell-Wagner-Sillars (MWS) polarization. Thus, in UDMA, water occurs as fragments that form non-freezing clusters. However, in unsilanated ZS-UDMA composites, bulk water can exist at the polymer-filler interface and form disordered structures of ice at low temperatures which can evaporate at high temperatures. Silanated ZS-UDMA composites function similarly to UDMA at low MC but are more plasticized at high temperatures. PMID:11350592

  2. Timer cover adhesive optimization

    SciTech Connect

    Carleton, J.J. II.

    1992-03-17

    The implementation of PROCODE as the data acquisition system for processing timers has required some modifications to the method of identifying timer assemblies. PROCODE requires machine-readable labelling of the assemblies. This report describes a series of experiments to find an adhesive that would keep labels attached to timers regardless of the condition of their surface when the label was applied and regardless of the heat, vibration, and shock they endured afterwards. The effect of the variation of these experimental factors on the performance of the adhesive was determined by using a Taguchi experimental design.

  3. Metallic Adhesion and Bonding

    NASA Technical Reports Server (NTRS)

    Ferrante, J.; Smith, J. R.; Rose, J. H.

    1984-01-01

    Although metallic adhesion has played a central part in much tribological speculation, few quantitative theoretical calculations are available. This is in part because of the difficulties involved in such calculations and in part because the theoretical physics community is not particularly involved with tribology. The calculations currently involved in metallic adhesion are summarized and shown that these can be generalized into a scaled universal relationship. Relationships exist to other types of covalent bonding, such as cohesive, chemisorptive, and molecular bonding. A simple relationship between surface energy and cohesive energy is offered.

  4. Elastomer toughened polyimide adhesives

    NASA Technical Reports Server (NTRS)

    St.clair, A. K.; St.clair, T. L. (Inventor)

    1983-01-01

    A rubber-toughened addition-type polyimide composition is disclosed which has excellent high temperature bonding characteristics in the fully cured state, and improved peel strength and adhesive fracture resistance physical property characteristics. The process for making the improved adhesive involves preparing the rubber containing amic acid prepolymer by chemically reacting an amine-terminated elastomer and an aromatic diamine with an aromatic dianhydride with which a reactive chain stopper anhydride was mixed, and utilizing solvent or mixture of solvents for the reaction.

  5. Synthesis, characterizations, and biocompatibility of block poly(ester-urethane)s based on biodegradable poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB) and poly(ε-caprolactone).

    PubMed

    Qiu, Handi; Li, Dandan; Chen, Xi; Fan, Kaiyan; Ou, Wenfeng; Chen, Kevin C; Xu, Kaitian

    2013-01-01

    A type of block poly(ester-urethane)s (abbreviated as PUBC) based on bacterial copolyester poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3/4HB) and biodegradable poly(ε-caprolactone) (PCL) was synthesized by melting polymerization using 1,6-hexamethylene diisocyanate (HDI) as the coupling agent, with different 3HB, 4HB and PCL contents and segment lengths. Stannous octanoate (Sn(Oct)(2)) was used as catalyst. The chemical structure, molecular weight and thermal property were characterized by (1)H NMR, FTIR GPC, DSC and TGA. DSC analysis revealed that the PUBC polyurethanes exhibit amorphous to semi-crystalline (20.9% crystallinity degree) with T(g) range from -39.7 to -21.5 °C. The hydrophilicity was investigated by static contact angle of deionized water and CH(2)I(2). The obtained PUBCs are hydrophobic (water contact angle 73.7-90.2°). Platelet adhesion study and plasma recalcification time revealed that the block polyurethanes possess hemastasis ability. CCK-8 assay illuminated that the no cytotoxic polyurethanes maintain rat aortic smooth muscle cells (RaSMCs) good viability. It was found that the 4HB content in the materials is an important factor to affect the sustainable cell viability. PMID:22826204

  6. Synthesis, characterization and drug release of biocompatible/biodegradable non-toxic poly(urethane urea)s based on poly(epsilon-caprolactone)s and lysine-based diisocyanate.

    PubMed

    Reddy, Thatiparti Thimma; Kano, Arihiro; Maruyama, Atsushi; Takahara, Atsushi

    2010-01-01

    Segmented poly(urethane urea)s (SPUUs) based on aliphatic diisocyanato (2,6-diisocyanato methyl caproate (lysine-based diisocyanate, LDI)), poly(epsilon-caprolactone diol)s (PCLs) with molecular weights 530, 1250 and 2000, and 1,4-butanediamine were synthesized in absence of catalyst. The resulting SPUUs, with different soft segment length, were characterized by suitable analytical techniques. The synthesized SPUUs had high molecular weights, low glass-transition temperatures (adhesion studies on these materials to investigate the biocompatibility. The synthesized SPUUs combine physical and bioresponsive and biodegradable properties that might be employed in wound dressing, drug delivery and tissue-engineering applications. PMID:20534197

  7. The M2 macrophages induce autophagic vascular disorder and promote mouse sensitivity to urethane-related lung carcinogenesis.

    PubMed

    Li, G-G; Guo, Z-Z; Ma, X-F; Cao, N; Geng, S-N; Zheng, Y-Q; Meng, M-J; Lin, H-H; Han, G; Du, G-J

    2016-06-01

    Tumor vessels are known to be abnormal, with typically aberrant, leaky and disordered vessels. Here, we investigated whether polarized macrophage phenotypes are involved in tumor abnormal angiogenesis and what is its mechanism. We found that there was no difference in chemotaxis of polarized M1 and M2 macrophages to lewis lung carcinoma (LLC) cells and that either M1 or M2 macrophage-conditioned media had no effect on LLC cell proliferation. Unexpectedly, the M2 but not M1 macrophage-conditioned media promoted the proliferation of human umbilical vein endothelial cells (HUVECs) and simultaneously increased endothelial cell permeability in vitro and angiogenic index in the chick embryo chorioallantoic membrane (CAM). The treatment with M2 but not M1 macrophage-conditioned media increased autophagosomes as well as microtubule-associated protein light chain 3B (LC3-B) expression (a robust marker of autophagosomes) but decreased p62 protein expression (a selective autophagy substrate) in HUVECs, the treatment with chloroquine that blocked autophagy abrogated the abnormal angiogenic efficacy of M2 macrophage-conditioned media. These results were confirmed in urethane-induced lung carcinogenic progression. Urethane-induced lung carcinogenesis led to more M2 macrophage phenotype and increased abnormal angiogenesis concomitant with the upregulation of LC3-B and the downregulation of p62. Clodronate liposome-induced macrophage depletion, chloroquine-induced autophagic prevention or salvianolic acid B-induced vascular protection decreased abnormal angiogenesis and lung carcinogenesis. In addition, we found that the tendency of age-related M2 macrophage polarization also promoted vascular permeability and carcinogenesis in urethane carcinogenic progression. These findings indicate that the M2 macrophages induce autophagic vascular disorder to promote lung cancer progression, and the autophagy improvement represents an efficacious strategy for abnormal angiogenesis and cancer

  8. Synthesis and characterization of novel elastomeric poly(D,L-lactide urethane) maleate composites for bone tissue engineering

    PubMed Central

    Mercado-Pagán, Ángel E.; Kang, Yunqing; Ker, Dai Fei Elmer; Park, Sangwon; Yao, Jeffrey; Bishop, Julius; Yang, Yunzhi

    2013-01-01

    Here, we report the synthesis and characterization of a novel 4-arm poly(lactic acid urethane)-maleate (4PLAUMA) elastomer and its composites with nano-hydroxyapatite (nHA) as potential weight-bearing composite. The 4PLAUMA/nHA ratios of the composites were 1:3, 2:5, 1:2 and 1:1. FTIR and NMR characterization showed urethane and maleate units integrated into the PLA matrix. Energy dispersion and Auger electron spectroscopy confirmed homogeneous distribution of nHA in the polymer matrix. Maximum moduli and strength of the composites of 4PLAUMA/nHA, respectively, are 1973.31 ± 298.53 MPa and 78.10 ± 3.82 MPa for compression, 3630.46 ± 528.32 MPa and 6.23 ± 1.44 MPa for tension, 1810.42 ± 86.10 MPa and 13.00 ± 0.72 for bending, and 282.46 ± 24.91 MPa and 5.20 ± 0.85 MPa for torsion. The maximum tensile strains of the polymer and composites are in the range of 5% to 93%, and their maximum torsional strains vary from 0.26 to 0.90. The composites exhibited very slow degradation rates in aqueous solution, from approximately 50% mass remaining for the pure polymer to 75% mass remaining for composites with high nHA contents, after a period of 8 weeks. Increase in ceramic content increased mechanical properties, but decreased maximum strain, degradation rate, and swelling of the composites. Human bone marrow stem cells and human endothelial cells adhered and proliferated on 4PLAUMA films and degradation products of the composites showed little-to-no toxicity. These results demonstrate that novel 4-arm poly(lactic acid urethane)-maleate (4PLAUMA) elastomer and its nHA composites may have potential applications in regenerative medicine. PMID:24817764

  9. A new peptide-based urethane polymer: synthesis, biodegradation, and potential to support cell growth in vitro

    PubMed Central

    Zhang, Jian Ying; Beckman, Eric J.; Piesco, Nicholas P.; Agarwal, Sudha

    2016-01-01

    A novel non-toxic biodegradable lysine-di-isocyanate (LDI)-based urethane polymer was developed for use in tissue engineering applications. This matrix was synthesized with highly purified LDI made from the lysine diethylester. The ethyl ester of LDI was polymerized with glycerol to form a prepolymer. LDI–glycerol prepolymer when reacted with water foamed with the liberation of CO2 to provide a pliable spongy urethane polymer. The LDI–glycerol matrix degraded in aqueous solutions at 100, 37, 22, and 4°C at a rate of 27.7, 1.8, 0.8, and 0.1 mM per 10 days, respectively. Its thermal stability in water allowed its sterilization by autoclaving. The degradation of the LDI–glycerol polymer yielded lysine, ethanol, and glycerol as breakdown products. The degradation products of LDI–glycerol polymer did not significantly affect the pH of the solution. The glass transition temperature (Tg) of this polymer was found to be 103.4°C. The physical properties of the polymer network were found to be adequate to support the cell growth in vitro, as evidenced by the fact that rabbit bone marrow stromal cells (BMSC) attached to the polymer matrix and remained viable on its surface. Culture of BMSC on LDI–glycerol matrix for long durations resulted in the formation of multilayered confluent cultures, a characteristic typical of bone cells. Furthermore, cells grown on LDI–glycerol matrix did not differ phenotypically from the cells grown on the tissue culture polystyrene plates as assessed by the cell growth, and expression of mRNA for collagen type I, and transforming growth factor-β1 (TGF-β1). The observations suggest that biodegradable peptide-based urethane polymers can be synthesized which may pave their way for possible use in tissue engineering applications. PMID:10811306

  10. Switchable bio-inspired adhesives

    NASA Astrophysics Data System (ADS)

    Kroner, Elmar

    2015-03-01

    Geckos have astonishing climbing abilities. They can adhere to almost any surface and can run on walls and even stick to ceilings. The extraordinary adhesion performance is caused by a combination of a complex surface pattern on their toes and the biomechanics of its movement. These biological dry adhesives have been intensely investigated during recent years because of the unique combination of adhesive properties. They provide high adhesion, allow for easy detachment, can be removed residue-free, and have self-cleaning properties. Many aspects have been successfully mimicked, leading to artificial, bio-inspired, patterned dry adhesives, and were addressed and in some aspects they even outperform the adhesion capabilities of geckos. However, designing artificial patterned adhesion systems with switchable adhesion remains a big challenge; the gecko's adhesion system is based on a complex hierarchical surface structure and on advanced biomechanics, which are both difficult to mimic. In this paper, two approaches are presented to achieve switchable adhesion. The first approach is based on a patterned polydimethylsiloxane (PDMS) polymer, where adhesion can be switched on and off by applying a low and a high compressive preload. The switch in adhesion is caused by a reversible mechanical instability of the adhesive silicone structures. The second approach is based on a composite material consisting of a Nickel- Titanium (NiTi) shape memory alloy and a patterned adhesive PDMS layer. The NiTi alloy is trained to change its surface topography as a function of temperature, which results in a change of the contact area and of alignment of the adhesive pattern towards a substrate, leading to switchable adhesion. These examples show that the unique properties of bio-inspired adhesives can be greatly improved by new concepts such as mechanical instability or by the use of active materials which react to external stimuli.

  11. FT-IR, 1H, 13C NMR, ESI-MS and semiempirical investigation of the structures of Monensin phenyl urethane complexes with the sodium cation.

    PubMed

    Huczyński, Adam

    2013-06-01

    In this paper three forms of phenyl urethane of Monensin i.e. its acid form (H-MU) and its 1:1 complex with NaClO4 (H-MU-Na) and its sodium salt (Na-MU) were obtained and their structures were studied by FT-IR, (1)H and (13)C NMR, ESI MS and PM5 methods. The FT-IR data of Na-MU complexes demonstrate that the C=O urethane group is not engaged in the complexation of the sodium cation. However spectroscopic studies of H-MU-Na complex show that the structure in which this C=O urethane groups participate in the complexation is also present, but it is in the minority. The PM5 semiempirical calculations allow visualisation of all structures and determination of the hydrogen bond parameters. PMID:23578536

  12. Synthesis and characterization of poly(D,L-lactide)-poly(ethylene glycol) multiblock poly(ether-ester-urethane)s

    NASA Astrophysics Data System (ADS)

    Haw, Tan Ching; Ahmad, Azizan; Anuar, Farah Hannan

    2015-09-01

    In this study, poly(D,L-lactide)-poly(ethylene glycol) multiblock poly(ether-ester-urethane)s was synthesized in the framework of environmental friendly products to meet the need for highly flexible polymers. Triblock copolymer with poly(ethylene glycol) as center block and poly(D,L-lactide) as side block were first synthesized by ring-opening polymerization of D,L-lactide, followed by chain extension reaction of triblocks using hexamethylene diisocyanate (HMDI). NMR and infra-red spectroscopies were used to determine the molecular composition whereas XRD analysis revealed crystallinity behavior of synthesized multiblock copolymers.

  13. Mössbauer spectroscopic study of FeII-doped sulphonated poly(ether-urethane)—styrene-acrylate copolymer

    NASA Astrophysics Data System (ADS)

    Kamnev, A. A.; Grigoryeva, O. P.; Fainleib, A. M.; Kuzmann, E.

    2013-04-01

    Thermoplastic linear ionomer based on sulphonated poly(ether-urethane)—styrene-acrylate copolymer, doped with natural Fe2 + , was studied by Mössbauer spectroscopy at T = 78 and 290 K to monitor the chemical state of Fe species. The Fe2 + added to aqueous suspension of the system was only partly oxidised in the course of polymer film preparation and drying in air. The oxidised part comprised a magnetic phase (~19 % of total Fe both at T = 78 and 298 K) and a quadrupole doublet (~40 %), while FeII (over 40 %) stabilised in two types of microenvironments.

  14. Potential use of a polycarbonate-urethane matrix reinforced with polyethylene fibers for shock-absorbing dental implants.

    PubMed

    Sheikhhassani, Ramtin; Anvari, Pasha; Taei, Simin; Sheikhhassani, Yasmin

    2015-09-01

    The absence of a shock-absorbing mechanism in commercial dental implants is a likely factor in the resulting bone loss and possible implant failure. The aim of the current study is to generate a shock-absorbing dental implant that resembles the periodontal ligament, which naturally absorbs occlusal overloading forces. To achieve this, a polycarbonate-urethane composite reinforced with polyethylene fibers will be constructed. Tests based on finite element analysis and mechanical testing are proposed to further examine this novel implant type. PMID:26008614

  15. Switchable Adhesion in Vacuum Using Bio-Inspired Dry Adhesives.

    PubMed

    Purtov, Julia; Frensemeier, Mareike; Kroner, Elmar

    2015-11-01

    Suction based attachment systems for pick and place handling of fragile objects like glass plates or optical lenses are energy-consuming and noisy and fail at reduced air pressure, which is essential, e.g., in chemical and physical vapor deposition processes. Recently, an alternative approach toward reversible adhesion of sensitive objects based on bioinspired dry adhesive structures has emerged. There, the switching in adhesion is achieved by a reversible buckling of adhesive pillar structures. In this study, we demonstrate that these adhesives are capable of switching adhesion not only in ambient air conditions but also in vacuum. Our bioinspired patterned adhesive with an area of 1 cm(2) provided an adhesion force of 2.6 N ± 0.2 N in air, which was reduced to 1.9 N ± 0.2 N if measured in vacuum. Detachment was induced by buckling of the structures due to a high compressive preload and occurred, independent of air pressure, at approximately 0.9 N ± 0.1 N. The switch in adhesion was observed at a compressive preload between 5.6 and 6.0 N and was independent of air pressure. The difference between maximum adhesion force and adhesion force after buckling gives a reasonable window of operation for pick and place processes. High reversibility of the switching behavior is shown over 50 cycles in air and in vacuum, making the bioinspired switchable adhesive applicable for handling operations of fragile objects. PMID:26457864

  16. Switchable Adhesion in Vacuum Using Bio-Inspired Dry Adhesives

    PubMed Central

    2015-01-01

    Suction based attachment systems for pick and place handling of fragile objects like glass plates or optical lenses are energy-consuming and noisy and fail at reduced air pressure, which is essential, e.g., in chemical and physical vapor deposition processes. Recently, an alternative approach toward reversible adhesion of sensitive objects based on bioinspired dry adhesive structures has emerged. There, the switching in adhesion is achieved by a reversible buckling of adhesive pillar structures. In this study, we demonstrate that these adhesives are capable of switching adhesion not only in ambient air conditions but also in vacuum. Our bioinspired patterned adhesive with an area of 1 cm2 provided an adhesion force of 2.6 N ± 0.2 N in air, which was reduced to 1.9 N ± 0.2 N if measured in vacuum. Detachment was induced by buckling of the structures due to a high compressive preload and occurred, independent of air pressure, at approximately 0.9 N ± 0.1 N. The switch in adhesion was observed at a compressive preload between 5.6 and 6.0 N and was independent of air pressure. The difference between maximum adhesion force and adhesion force after buckling gives a reasonable window of operation for pick and place processes. High reversibility of the switching behavior is shown over 50 cycles in air and in vacuum, making the bioinspired switchable adhesive applicable for handling operations of fragile objects. PMID:26457864

  17. Adept Adhesion Reduction Solution

    MedlinePlus

    ... icodextrin. The fluid is used during or after laparoscopic gynecological surgery to separate and protect tissues and decrease the number of new adhesions after surgery. Adept® is supplied sterile, in a single-use bag. How does it work? During surgery, ...

  18. Adhesion molecules and receptors

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Adhesion molecules are necessary for leukocyte trafficking and differentiation. They serve to initiate cell-cell interactions under conditions of shear, and they sustain the cell-cell and cell-matrix interactions needed for cellular locomotion. They also can serve directly as signaling molecules act...

  19. Wood Composite Adhesives

    NASA Astrophysics Data System (ADS)

    Gomez-Bueso, Jose; Haupt, Robert

    The global environment, in which phenolic resins are being used for wood composite manufacture, has changed significantly during the last decade. This chapter reviews trends that are driving the use and consumption of phenolic resins around the world. The review begins with recent data on volume usage and regional trends, followed by an analysis of factors affecting global markets. In a section on environmental factors, the impact of recent formaldehyde emission regulations is discussed. The section on economics introduces wood composite production as it relates to the available adhesive systems, with special emphasis on the technical requirement to improve phenolic reactivity. Advances in composite process technology are introduced, especially in regard to the increased demands the improvements place upon adhesive system performance. The specific requirements for the various wood composite families are considered in the context of adhesive performance needs. The results of research into current chemistries are discussed, with a review of recent findings regarding the mechanisms of phenolic condensation and acceleration. Also, the work regarding alternate natural materials, such as carbohydrates, lignins, tannins, and proteinaceous materials, is presented. Finally, new developments in alternative adhesive technologies are reported.

  20. Rapid adhesive bonding concepts

    NASA Technical Reports Server (NTRS)

    Stein, B. A.; Tyeryar, J. R.; Hodges, W. T.

    1984-01-01

    Adhesive bonding in the aerospace industry typically utilizes autoclaves or presses which have considerable thermal mass. As a consequence, the rates of heatup and cooldown of the bonded parts are limited and the total time and cost of the bonding process is often relatively high. Many of the adhesives themselves do not inherently require long processing times. Bonding could be performed rapidly if the heat was concentrated in the bond lines or at least in the adherends. Rapid adhesive bonding concepts were developed to utilize induction heating techniques to provide heat directly to the bond line and/or adherends without heating the entire structure, supports, and fixtures of a bonding assembly. Bonding times for specimens are cut by a factor of 10 to 100 compared to standard press bonding. The development of rapid adhesive bonding for lap shear specimens (per ASTM D1003 and D3163), for aerospace panel bonding, and for field repair needs of metallic and advanced fiber reinforced polymeric matrix composite structures are reviewed.

  1. Adhesion testing of aircraft tires

    NASA Technical Reports Server (NTRS)

    Bobo, S. N.

    1983-01-01

    Adhesion testing appeared to offer a less burdensome alternative to replace some of the dynamometer tests. Accordingly, test results and data were requested from retreaders who had used adhesion testing.

  2. Resistance heating releases structural adhesive

    NASA Technical Reports Server (NTRS)

    Glemser, N. N.

    1967-01-01

    Composite adhesive package bonds components together for testing and enables separation when testing is completed. The composite of adhesives, insulation and a heating element separate easily when an electrical current is applied.

  3. 3-D foam adhesive deposition

    NASA Technical Reports Server (NTRS)

    Lemons, C. R.; Salmassy, O. K.

    1976-01-01

    Bonding method, which reduces amount and weight of adhesive, is applicable to foam-filled honeycomb constructions. Novel features of process include temperature-viscosity control and removal of excess adhesive by transfer to cellophane film.

  4. Coating Reduces Ice Adhesion

    NASA Technical Reports Server (NTRS)

    Smith, Trent; Prince, Michael; DwWeese, Charles; Curtis, Leslie

    2008-01-01

    The Shuttle Ice Liberation Coating (SILC) has been developed to reduce the adhesion of ice to surfaces on the space shuttle. SILC, when coated on a surface (foam, metal, epoxy primer, polymer surfaces), will reduce the adhesion of ice by as much as 90 percent as compared to the corresponding uncoated surface. This innovation is a durable coating that can withstand several cycles of ice growth and removal without loss of anti-adhesion properties. SILC is made of a binder composed of varying weight percents of siloxane(s), ethyl alcohol, ethyl sulfate, isopropyl alcohol, and of fine-particle polytetrafluoroethylene (PTFE). The combination of these components produces a coating with significantly improved weathering characteristics over the siloxane system alone. In some cases, the coating will delay ice formation and can reduce the amount of ice formed. SILC is not an ice prevention coating, but the very high water contact angle (greater than 140 ) causes water to readily run off the surface. This coating was designed for use at temperatures near -170 F (-112 C). Ice adhesion tests performed at temperatures from -170 to 20 F (-112 to -7 C) show that SILC is a very effective ice release coating. SILC can be left as applied (opaque) or buffed off until the surface appears clear. Energy dispersive spectroscopy (EDS) and x-ray photoelectron spectroscopy (XPS) data show that the coating is still present after buffing to transparency. This means SILC can be used to prevent ice adhesion even when coating windows or other objects, or items that require transmission of optical light. Car windshields are kept cleaner and SILC effectively mitigates rain and snow under driving conditions.

  5. Involvement of EZH2, SUV39H1, G9a and associated molecules in pathogenesis of urethane induced mouse lung tumors: Potential targets for cancer control

    SciTech Connect

    Pandey, Manuraj; Sahay, Satya; Tiwari, Prakash; Upadhyay, Daya S.; Sultana, Sarwat; Gupta, Krishna P.

    2014-10-15

    In the present study, we showed the correlation of EZH2, SUV39H1 or G9a expression and histone modifications with the urethane induced mouse lung tumorigenesis in the presence or absence of antitumor agent, inositol hexaphosphate (IP6). Tumorigenesis and the molecular events involved therein were studied at 1, 4, 12 or 36 weeks after the exposure. There were no tumors at 1 or 4 weeks but tumors started appearing at 12 weeks and grew further till 36 weeks after urethane exposure. Among the molecular events, upregulation of EZH2 and SUV39H1 expressions appeared to be time dependent, but G9a expression was altered significantly only at later stages of 12 or 36 weeks. Alteration in miR-138 expression supports the upregulation of its target, EZH2. H3K9me2, H3K27me3 or H4K20me3 was found to be altered at 12 or 36 weeks. However, ChIP analysis of p16 and MLH1 promoters showed their binding with H3K9me2 and H3K27me3 which was maximum at 36 weeks. Thus, histone modification and their interactions with gene promoter resulted in the reduced expression of p16 and MLH1. IP6 prevented the incidence and the size of urethane induced lung tumors. IP6 also prevented the urethane induced alterations in EZH2, SUV39H1, G9a expressions and histone modifications. Our results suggest that the alterations in the histone modification pathways involving EZH2 and SUV39H1 expressions are among the early events in urethane induced mouse lung tumorigenesis and could be exploited for cancer control. - Highlights: • Urethane induces mouse lung tumor in a time dependent manner. • EZH2, SUV39H1, G9a induced by urethane and progress with time • Downregulation of miRNA-138 supports the EZH2 upregulation. • Methylation of histones showed a consequence of upregulated EZH2, SUV39H1 and G9a. • IP6 inhibits urethane induced changes and prevents tumor development.

  6. Fmoc solid-phase synthesis of C-terminal modified peptides by formation of a backbone cyclic urethane moiety.

    PubMed

    Elashal, Hader E; Cohen, Ryan D; Raj, Monika

    2016-08-11

    C-terminally modified peptides are of high significance due to the therapeutic properties that accompany various C-terminal functional groups and the ability to manipulate them for further applications. Thus, there is a great necessity for an effective solid phase technique for the synthesis of C-terminally modified peptides. Here, we report a universal solid phase strategy for the synthesis of various C-terminal modified peptides which is independent of the type of resins, linkers, and unnatural moieties typically needed for C-terminal modifications. The technique proceeds by the modification of C-terminal serine to a cyclic urethane moiety which results in the activation of the backbone amide chain for nucleophilic displacement by various nucleophiles to generate C-terminally modified acids, esters, N-aryl amides, and alcohols. This cyclic urethane technique (CUT) also provides a general strategy for synthesis of C-terminal protected peptides that can be used for convergent synthesis of large peptides. The C-terminal protecting groups are cleaved by facile hydrolysis to release the free peptide. PMID:27407005

  7. Focal Adhesion Kinase-Dependent Regulation of Adhesive Force Involves Vinculin Recruitment to Focal Adhesions

    PubMed Central

    Hanks, Steven K.; García, Andrés J.

    2016-01-01

    Background information Focal adhesion kinase (FAK), an essential non-receptor tyrosine kinase, plays pivotal roles in migratory responses, adhesive signaling, and mechanotransduction. FAK-dependent regulation of cell migration involves focal adhesion turnover dynamics as well as actin cytoskeleton polymerization and lamellipodia protrusion. Whereas roles for FAK in migratory and mechanosensing responses have been established, the contributions of FAK to the generation of adhesive forces are not well understood. Results Using FAK-null cells expressing wild-type and mutant FAK under an inducible tetracycline promoter, we analyzed the role of FAK in the generation of steady-state adhesive forces using micropatterned substrates and a hydrodynamic adhesion assay. FAK expression reduced steady-state strength by 30% compared to FAK-null cells. FAK expression reduced vinculin localization to focal adhesions by 35% independently from changes in integrin binding and localization of talin and paxillin. RNAi knockdown of vinculin abrogated the FAK-dependent differences in adhesive force. FAK-dependent changes in vinculin localization and adhesive force were confirmed in human primary fibroblasts with FAK knocked down by RNAi. The autophosphorylation Y397 and kinase domain Y576/Y577 sites were differentially required for FAK-mediated adhesive responses. Conclusions We demonstrate that FAK reduces steady-state adhesion strength by modulating vinculin recruitment to focal adhesions. These findings provide insights into the role of FAK in mechanical interactions between a cell and the extracellular matrix. PMID:19883375

  8. Adhesion behaviors on superhydrophobic surfaces.

    PubMed

    Zhu, Huan; Guo, Zhiguang; Liu, Weimin

    2014-04-18

    The adhesion behaviors of superhydrophobic surfaces have become an emerging topic to researchers in various fields as a vital step in the interactions between materials and organisms/materials. Controlling the chemical compositions and topological structures via various methods or technologies is essential to fabricate and modulate different adhesion properties, such as low-adhesion, high-adhesion and anisotropic adhesion on superhydrophobic surfaces. We summarize the recent developments in both natural superhydrophobic surfaces and artificial superhydrophobic surfaces with various adhesions and also pay attention to superhydrophobic surfaces switching between low- and high-adhesion. The methods to regulate or translate the adhesion of superhydrophobic surfaces can be considered from two perspectives. One is to control the chemical composition and change the surface geometric structure on the surfaces, respectively or simultaneously. The other is to provide external stimulations to induce transitions, which is the most common method for obtaining switchable adhesions. Additionally, adhesion behaviors on solid-solid interfaces, such as the behaviors of cells, bacteria, biomolecules and icing on superhydrophobic surfaces are also noticeable and controversial. This review is aimed at giving a brief and crucial overview of adhesion behaviors on superhydrophobic surfaces. PMID:24575424

  9. Clinical Recommendation: Labial Adhesions.

    PubMed

    Bacon, Janice L; Romano, Mary E; Quint, Elisabeth H

    2015-10-01

    Labial adhesions, also known as labial agglutination, are a common finding in prepubertal adolescents. They are defined as fusion of the labia minora in the midline or are termed vulvar adhesions when they occur below the labia minora (inner labia). Patients are often asymptomatic but might present with genitourinary complaints. The decision for treatment is based on symptoms. The mainstay of treatment in asymptomatic patients is conservative, with careful attention to vulvar hygiene and reassurance to parents. In symptomatic patients, topical treatment with estrogen and/or steroid cream is often curative. Less often, corrective surgery is necessary. Recurrence is common until a patient goes through puberty. These recommendations are intended for pediatric and gynecologic health care providers who care for pediatric and adolescent girls to facilitate diagnosis and treatment. PMID:26162697

  10. Environmentally compliant adhesive joining technology

    SciTech Connect

    Tira, J.S.

    1996-08-01

    Adhesive joining offers one method of assembling products. Advantages of adhesive joining/assembly include distribution of applied forces, lighter weight, appealing appearance, etc. Selecting environmentally safe adhesive materials and accompanying processes is paramount in today`s business climate if a company wants to be environmentally conscious and stay in business. Four areas of adhesive joining (adhesive formulation and selection, surface preparation, adhesive bonding process, waste and pollution generation/cleanup/management) all need to be carefully evaluated before adhesive joining is selected for commercial as well as military products. Designing for six sigma quality must also be addressed in today`s global economy. This requires material suppliers and product manufacturers to work even closer together.

  11. Improved wettability and adhesion of polylactic acid/chitosan coating for bio-based multilayer film development

    NASA Astrophysics Data System (ADS)

    Gartner, Hunter; Li, Yana; Almenar, Eva

    2015-03-01

    The objective of this study was to investigate the effect of methyldiphenyl diisocyanate (MDI) concentration (0, 0.2, 1, 2, and 3%) on the wettability and adhesion of blend solutions of poly(lactic acid) (PLA) and chitosan (CS) when coated on PLA film for development of a bio-based multi-layer film suitable for food packaging and other applications. Characterization was carried out by attenuated total reflectance infrared spectrometry (ATR-FTIR), contact angle (θ), mechanical adhesion pull-off testing, and scanning electron microscopy (SEM). The θ of the PLA/CS blend shifted to a lower value (41-35°) with increasing MDI concentration showing that the surface tension was modified between the PLA/CS blend solution and PLA film and better wettability was achieved. The increase in MDI also resulted in an increased breaking strength (228-303 kPa) due to the increased H-bonding resulting from the more urethane groups formed within the PLA/CS blend as shown by ATR-FTIR. The improved adhesion was also shown by the increased number of physical entanglements observed by SEM. It can be concluded that MDI can be used to improve wettability and adhesion between PLA/CS coating and PLA film.

  12. Development of phosphorylated adhesives

    NASA Technical Reports Server (NTRS)

    Bilow, N.; Giants, T. W.; Jenkins, R. K.; Campbell, P. L.

    1983-01-01

    The synthesis of epoxy prepolymers containing phosphorus was carried out in such a manner as to provide adhesives containing at least 5 percent of this element. The purpose of this was to impart fire retardant properties to the adhesive. The two epoxy derivatives, bis(4-glycidyl-oxyphenyl)phenylphosphine oxide and bis(4-glycidyl-2-methoxyphenyl)phenylphosphonate, and a curing agent, bis(3-aminophenyl)methylphosphine oxide, were used in conjunction with one another and along with conventional epoxy resins and curing agents to bond Tedlar and Polyphenylethersulfone films to Kerimid-glass syntactic foam-filled honeycomb structures. Elevated temperatures are required to cure the epoxy resins with the phosphorus-contaning diamine; however, when Tedlar is being bonded, lower curing temperatures must be used to avoid shrinkage and the concomitant formation of surface defects. Thus, the phosphorus-containing aromatic amine curing agent cannot be used alone, although it is possible to use it in conjunction with an aliphatic amine which would allow lower cure temperatures to be used. The experimental epoxy resins have not provided adhesive bonds quite as strong as those provided by Epon 828 when compared in peel tests, but the differences are not very significant. It should be noted, if optimum properties are to be realized. In any case the fire retardant characteristics of the neat resin systems obtained are quite pronounced, since in most cases the self-extinguishing properties are evident almost instantly when specimens are removed from a flame.

  13. Ceramic microstructure and adhesion

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1984-01-01

    When a ceramic is brought into contact with a ceramic, a polymer, or a metal, strong bond forces can develop between the materials. The bonding forces will depend upon the state of the surfaces, cleanliness and the fundamental properties of the two solids, both surface and bulk. Adhesion between a ceramic and another solid are discussed from a theoretical consideration of the nature of the surfaces and experimentally by relating bond forces to interface resulting from solid state contact. Surface properties of ceramics correlated with adhesion include, orientation, reconstruction and diffusion as well as the chemistry of the surface specie. Where a ceramic is in contact with a metal their interactive chemistry and bond strength is considered. Bulk properties examined include elastic and plastic behavior in the surficial regions, cohesive binding energies, crystal structures and crystallographic orientation. Materials examined with respect to interfacial adhesive interactions include silicon carbide, nickel zinc ferrite, manganese zinc ferrite, and aluminum oxide. The surfaces of the contacting solids are studied both in the atomic or molecularly clean state and in the presence of selected surface contaminants.

  14. Flexible urethane foams and chlorofluorocarbon emissions: a support document for economic implications of regulating chlorofluorocarbon emissions from nonaerosol applications. Final report

    SciTech Connect

    Mooz, W.E.; Quinn, T.H.

    1980-06-01

    The methods used to proceed from the historical to the analysis of policies that might reduce chlorofluorocarbon emissions are addressed. Flexable urethane foam plants are a significant point source of CFC emissions. Recovery of CFC or methylene chloride conversion are recommended to reduce CFC releases to the atmosphere. Cost factors are also considered.

  15. Polyurethane adhesive ingestion.

    PubMed

    Fitzgerald, Kevin T; Bronstein, Alvin C

    2013-02-01

    Polyurethane adhesives are found in a large number of household products in the United States and are used for a variety of purposes. Several brands of these expanding wood glues (those containing diphenylmethane diisocyanate [MDI]) have the potential to form gastrointestinal (GI) foreign bodies if ingested. The ingested adhesive forms an expanding ball of glue in the esophagus and gastric lumen. This expansion is caused by a polymerization reaction using the heat, water, and gastric acids of the stomach. A firm mass is created that can be 4-8 times its original volume. As little as 2 oz of glue have been reported to develop gastric foreign bodies. The obstructive mass is reported to form within minutes of ingestion of the adhesive. The foreign body can lead to esophageal impaction and obstruction, airway obstruction, gastric outflow obstruction, mucosal hemorrhage, ulceration, laceration, perforation of the esophageal and gastric linings, and death. Clinical signs following ingestion include anorexia, lethargy, vomiting, tachypnea, and abdominal distention and pain, and typically develop within 12 hours. Clinical signs may depend upon the size of the mass. If left untreated, perforation and rupture of the esophagus or stomach can occur. The glue mass does not stick to the GI mucosa and is not always detectable on abdominal palpation. Radiographs are recommended to confirm the presence of the "glue-ball" foreign body, and radiographic evidence of the obstruction may be seen as early as 4-6 hours following ingestion. Emesis is contraindicated owing to the risk of aspiration of the glue into the respiratory tree or the subsequent lodging of the expanding glue mass in the esophagus. Likewise, efforts to dilute the glue and prevent the formation of the foreign body through administration of liquids, activated charcoal, or bulk-forming products to push the foreign body through the GI tract have proven ineffective. Even endoscopy performed to remove the foreign body has

  16. Silver nanowire networks embedded in urethane acrylate for flexible capacitive touch sensor

    NASA Astrophysics Data System (ADS)

    Kim, Youngmin; Kim, Jong-Woong

    2016-02-01

    Flexible electrodes based on a percolated network of silver nanowires (AgNWs) and polymer are considered one of the best candidates for fabrication of flexible and even rollable touch sensors. A general approach to make the AgNW transparent electrode is based on an overcoating of AgNW dispersion onto a pre-formed transparent film. However, in that case, the nanowires could be easily detached from the film, because of the poor adhesion between them. Herein an inverted layer processing method has been employed to bury the AgNWs into the surface of a transparent polymer to enhance the adhesion. For this, a highly stiff and transparent polyurethane acrylate (PUA) was newly designed and synthesized by adding a cross-linker to the pre-polymer, with AgNWs patterned for a capacitive sensor then being successfully embedded in its surface to produce. By this unique structure with the PUA, highly transparent, conductive and mechanically more reliable capacitive touch sensor could be fabricated. The sensing capability and mechanical stability were confirmed by cyclic bend testing to a curvature radius of 0.5 mm.

  17. JKR adhesion in cylindrical contacts

    NASA Astrophysics Data System (ADS)

    Sundaram, Narayan; Farris, T. N.; Chandrasekar, S.

    2012-01-01

    Planar JKR adhesive solutions use the half-plane assumption and do not permit calculation of indenter approach or visualization of adhesive force-displacement curves unless the contact is periodic. By considering a conforming cylindrical contact and using an arc crack analogy, we obtain closed-form indenter approach and load-contact size relations for a planar adhesive problem. The contact pressure distribution is also obtained in closed-form. The solutions reduce to known cases in both the adhesion-free and small-contact solution ( Barquins, 1988) limits. The cylindrical system shows two distinct regimes of adhesive behavior; in particular, contact sizes exceeding the critical (maximum) size seen in adhesionless contacts are possible. The effects of contact confinement on adhesive behavior are investigated. Some special cases are considered, including contact with an initial neat-fit and the detachment of a rubbery cylinder from a rigid cradle. A comparison of the cylindrical solution with the half-plane adhesive solution is carried out, and it indicates that the latter typically underestimates the adherence force. The cylindrical adhesive system is novel in that it possesses stable contact states that may not be attained even on applying an infinite load in the absence of adhesion.

  18. Permeability of dye through poly(urea-urethane) microcapsule membrane prepared from mixtures of di- and tri-isocyanate.

    PubMed

    Chang, Chih Pong; Chang, Jer Chen; Ichikawa, Kimio; Dobashi, Toshiaki

    2005-09-01

    Poly(urea-urethane) microcapsules were prepared by the interfacial polymerization with using mixtures of tri- and di-isocyanate monomers as wall forming materials, and dioctyl phthalate containing an oil-soluble dye as a core material. The time course of the dye release in dispersing tetrahydrofuran was measured as a function of the weight fraction of tri-isocyanate monomer in the total monomer w and the core/wall material-weight ratio g. The dye release curves were well represented by an exponential function C=Ceq(1-e-t/tau), where C is the concentration of the dye in the dispersing medium, Ceq that at equilibrium state, t the elution time and tau is a time constant. tau increased linearly against w at high g, suggesting controllability of the release rate of microcapsules by varying tri-isocyanate/di-isocyanate ratio. PMID:16081257

  19. Mössbauer spectroscopic study of sulphonated poly(ether-urethane) linear ionomer doped with iron species

    NASA Astrophysics Data System (ADS)

    Kamnev, A. A.; Grigoryeva, O. P.; Kuzmann, E.; Vértes, A.

    2009-04-01

    Thermoplastic linear poly(ether-urethane) sulphonated ionomer (PEUSI), doped with natural Fe2 + , was studied by Mössbauer spectroscopy at T = 78 and 290 K in order to monitor the chemical state of Fe species. The Fe2 + added was found to get only partly oxidised in the course of preparation of a dry polymer film from aqueous suspension. The oxidised part gave a ferric quadrupole doublet (over half of total Fe added) and, at T = 78 K only, a small portion of magnetically split sextet (ca. 3%), whereas FeII (total over 40%) stabilised in two different forms (represented by quadrupole doublets) corresponding to two types of iron(II) microenvironments, where FeII could be coordinated involving -CONH- and -NHNH- moieties and sulphonate groups in PEUSI. The results obtained show that Fe2 + -doping of PEUSI-based materials may be used for probing their structural characteristics by Mössbauer spectroscopy.

  20. Characterization of a poly(ether urethane)-based controlled release membrane system for delivery of ketoprofen

    NASA Astrophysics Data System (ADS)

    Macocinschi, Doina; Filip, Daniela; Vlad, Stelian; Oprea, Ana Maria; Gafitanu, Carmen Anatolia

    2012-10-01

    A poly(ether urethane) based on polytetrahydrofuran containing hydroxypropyl cellulose for biomedical applications was tested for its biocompatibility. Ketoprofen was incorporated (3% and 6%) in the polyurethane matrix as an anti-inflammatory drug. Kinetic and drug release mechanisms were studied. The pore size and pore size distribution of the polyurethane membranes were investigated by scanning electron microscopy. Surface tension characteristics as well as moisture sorption properties such as diffusion coefficients and equilibrium moisture contents of the membrane material were studied. It was found that kinetics and release mechanisms are in function of medium pH, composition of polymer-drug system, pore morphology and pore size distribution. Prolonged nature of release of ketoprofen is assured by low amount of drug in polyurethane membrane and physiological pH.

  1. Modeling the Adsorption of Hydrophobic Ethoxylated Urethane (HEUR) Thickeners onto Latex Surfaces using Self-Consistent Field Theory

    NASA Astrophysics Data System (ADS)

    Ginzburg, Valeriy; van Dyk, Antony; Chatterjee, Tirtha; Wang, Shihu; Larson, Ronald

    2015-03-01

    Hydrophobic Ethoxylated Urethane (HEUR) polymers are widely used as rheology modifiers (thickeners) in waterborne latex paints. Recently, it has been shown that the thickening effect of HEURs in paints is largely determined by their adsorption onto latex surfaces, this adsorption being a function of polymer structure, latex surface chemistry, and total available latex surface. Here, we describe the application of Self-Consistent Field Theory (SCFT) to calculate adsorption isotherms of several model HEURs onto ideal hydrophobic latex surfaces. Unlike earlier SCFT studies of adsorption, we explicitly take into account the role of HEUR micelles and competition between adsorption and micellization. The results are compared with experimental data and coarse-grained molecular dynamic (CG-MD) simulations, and good qualitative and semi-quantitative agreement is found. This work was supported by The Dow Chemical Company.

  2. Catalytic properties of maltogenic α-amylase from Bacillus stearothermophilus immobilized onto poly(urethane urea) microparticles.

    PubMed

    Straksys, Antanas; Kochane, Tatjana; Budriene, Saulute

    2016-11-15

    The immobilization of maltogenic α-amylase from Bacillus stearothermophilus (BsMa) onto novel porous poly(urethane urea) (PUU) microparticles synthesized from poly(vinyl alcohol) and isophorone diisocyanate was performed by covalent attachment to free isocyanate groups from PUU microparticles, or by physical adsorption of enzyme onto the surface of the carrier. The influence of structure, surface area and porosity of microparticles on the catalytic properties of immobilized BsMa was evaluated. The highest efficiency of immobilization of BsMa was found to be 72%. Optimal activity of immobilized BsMa was found to have increased by 10°C compared with the native enzyme. Influence of concentration of sodium chloride on activity of immobilized BsMa was evaluated. High storage and thermal stability and reusability for starch hydrolysis of immobilized enzyme were obtained. Immobilized BsMa has a great potential for biotechnology. PMID:27283635

  3. Biocompatibility of Synthetic Poly(ester urethane)/Polyhedral Oligomeric Silsesquioxane Matrices with Embryonic Stem Cell Proliferation and Differentiation

    PubMed Central

    Guo, Yan-Lin; Wang, Wenshou; Otaigbe, Joshua U.

    2010-01-01

    Incorporation of polyhedral oligomeric silsesquioxanes (POSS) into poly (ester urethane)s (PEU) as a building block results in a PEU/POSS hybrid polymer with increased mechanical strength and thermostability. An attractive feature of the new polymer is that it forms a porous matrix when cast in the form of a thin film, making it potentially useful in tissue engineering. In this study, we present detailed microscopic analysis of the PEU/POSS matrix and demonstrate its biocompatibility with cell culture. The PEU/POSS polymer forms a continuous porous matrix with open pores and interconnected grooves. From SEM image analysis, it is calculated that there are about 950 pores per mm2 of the matrix area with pore size ranging from 1 to 15 μm in diameter. The area occupied by the pores represents approximately 7.6 % of matrix area. Using mouse embryonic stem cells (ESCs), we demonstrate that the PEU/POSS matrix provides excellent support for cell proliferation and differentiation. Under the cell culture condition optimized to maintain self-renewal, ESCs grown on a PEU/POSS matrix exhibit undifferentiated morphology, express pluripotency markers, and have similar growth rate to cells grown on gelatin. When induced for differentiation, ESCs underwent dramatic morphological change, characterized by the loss of clonogenecity and increased cell size with well-expanded cytoskeleton networks. Differentiated cells are able to form a continuous monolayer that is closely embedded on the matrix. The excellent compatibility between the PEU/POSS matrix and ESC proliferation/differentiation demonstrates the potential of using PEU/POSS polymers in future ESC-based tissue engineering. PMID:20213627

  4. Removal of toluene and benzene from flue gas by a biotrickling filtration system which uses an urethane foam filter

    SciTech Connect

    Yamashita, Shigeki; Kitagawa, Mashayoshi

    1998-12-31

    A lab-scale research was conducted to study the toluene/benzene removal performance of a biotrickling filtration system. Urethane foam, which constituted a lattice-like structure internally, was used as the microbial carrier for the removal. This structure was found to be effective for minimizing drops in pressure (due to clogging), even under high space velocity conditions. The large specific surface area of the carrier (1200 m2/m3) also contributed to better removal performance. The space velocity (versus the packed bed) at 500 h-1(100 h-1 for most conventional biofiltration systems). Provided the target removal performance is obtained by such configuration, it may become possible to reduce the size of the biofiltration packed bed to one-fifth of that of conventional biofiltration systems. The test apparatus included a hard vinyl chloride column into which the microbial carrier was charged (layer of 500 mm). A nutrient solution, consisting of tap water mixed with nitrogen and phosphorus, was intermittently supplied into the column. The supply of nitrogen sources for microbial growth was regulated (ratio by weight versus the organic carbon load: Nitrogen:Carbon = 15:100) for improving removal performance. The temperature inside the column was maintained at 25. The flue gas was prepared by using reagent grade chemicals. The concentration of toluene and benzene was set at about 30 ppm. Following treatment of two months, the average removal percentages of toluene and benzene were 82% and 62%, respectively. On the other hand, average pressure drops (due to clogging) of the same were small, 12.8 mmH{sub 2}O/m and 7.2 mmH{sub 2}O/m, respectively. Such results indicated that this biotrickling filtration system using urethane foam has great potential as a considerably downsized system.

  5. Long-term in vitro stability assessment of polycarbonate urethane micro catheters: resistance to oxidation and stress cracking.

    PubMed

    Chandy, Thomas; Van Hee, Justin; Nettekoven, William; Johnson, Jay

    2009-05-01

    Micro catheter tubes were prepared from poly (carbonate urethane) (PCU, Bionate) and poly (ether urethane) (PEU, Pellethane) and their stability was investigated in vitro under applied strain. The tubes were stretched to an elongation of 200% or 300% and exposed to hydrogen peroxide/cobalt chloride (H(2)O(2)/CoCl(2)) solution for specific periods of time (up to 10 months). The samples were observed for surface degradation via scanning electron microscopy, the bulk erosion via the weight difference, and the changes in molecular weight using gel permeation chromatography. The 200% and 300% strained Pellethane tubes kept in H(2)O(2)/CoCl(2) solution for 1 month showed substantial cracking of the surface layer with pitting and have degraded completely within 45 to 60 days (from scanning electron microscopy). Bionate tubes treated in similar conditions for a 10-month period exhibited minute surface erosion in the depth of 0.25-1 microm and showed no evidence of major cracking or pitting. The gel permeation chromatography analysis of 300% strained catheters indicated that the degradation of Bionate tubes was negligible. The 10-month samples had shown approximately 18% reduction in their number average molecular weight (M(n)) and about 8% reduction in weight average molecular weight (M(w)). The Pellethane studied in similar conditions had indicated approximately 72% reduction in M(n) and about approximately 50% reduction in M(w) for 1 month. Overall, the Bionate underwent less degradation and the degradated surface layer was much thinner than Pellethane. These in vitro results are valuable in designing the in vivo studies for using Bionate tube as a long-term implant. PMID:18837455

  6. Stickiness--some fundamentals of adhesion.

    PubMed

    Gay, Cyprien

    2002-12-01

    We review some adhesion mechanisms that have been understood in the field of synthetic adhesives, and more precisely for adhesives that adhere instantaneously (a property named tackiness) and whose adhesive strength usually depends on the applied pressure (pressure-sensitive adhesives). The discussion includes effects of surface roughness, elasticity, cavitation, viscous and elastic fingering, substrate flexibility. PMID:21680396

  7. Effect of adhesive thickness on adhesively bonded T-joint

    NASA Astrophysics Data System (ADS)

    Abdullah, A. R.; Afendi, Mohd; Majid, M. S. Abdul

    2013-12-01

    The aim of this work is to analyze the effect of adhesive thickness on tensile strength of adhesively bonded stainless steel T-joint. Specimens were made from SUS 304 Stainless Steel plate and SUS 304 Stainless Steel perforated plate. Four T-joint specimens with different adhesive thicknesses (0.5, 1.0, 1.5 and 2.0 mm) were made. Experiment result shows T-joint specimen with adhesive thickness of 1.0 mm yield highest maximum load. Identical T-joint specimen jointed by spot welding was also tested. Tensile test shows welded T-Joint had eight times higher tensile load than adhesively bonded T-joint. However, in low pressure application such as urea granulator chamber, high tensile strength is not mandatory. This work is useful for designer in fertilizer industry and others who are searching for alternative to spot welding.

  8. Improved Adhesion and Compliancy of Hierarchical Fibrillar Adhesives.

    PubMed

    Li, Yasong; Gates, Byron D; Menon, Carlo

    2015-08-01

    The gecko relies on van der Waals forces to cling onto surfaces with a variety of topography and composition. The hierarchical fibrillar structures on their climbing feet, ranging from mesoscale to nanoscale, are hypothesized to be key elements for the animal to conquer both smooth and rough surfaces. An epoxy-based artificial hierarchical fibrillar adhesive was prepared to study the influence of the hierarchical structures on the properties of a dry adhesive. The presented experiments highlight the advantages of a hierarchical structure despite a reduction of overall density and aspect ratio of nanofibrils. In contrast to an adhesive containing only nanometer-size fibrils, the hierarchical fibrillar adhesives exhibited a higher adhesion force and better compliancy when tested on an identical substrate. PMID:26167951

  9. Hydrophilic PCU scaffolds prepared by grafting PEGMA and immobilizing gelatin to enhance cell adhesion and proliferation.

    PubMed

    Shi, Changcan; Yuan, Wenjie; Khan, Musammir; Li, Qian; Feng, Yakai; Yao, Fanglian; Zhang, Wencheng

    2015-05-01

    Gelatin contains many functional motifs which can modulate cell specific adhesion, so we modified polycarbonate urethane (PCU) scaffold surface by immobilization of gelatin. PCU-g-gelatin scaffolds were prepared by direct immobilizing gelatins onto the surface of aminated PCU scaffolds. To increase the immobilization amount of gelatin, poly(ethylene glycol) methacrylate (PEGMA) was grafted onto PCU scaffolds by surface initiated atom transfer radical polymerization. Then, following amination and immobilization, PCU-g-PEGMA-g-gelatin scaffolds were obtained. Both modified scaffolds were characterized by chemical and biological methods. After immobilization of gelatin, the microfiber surface became rough, but the original morphology of scaffolds was maintained successfully. PCU-g-PEGMA-g-gelatin scaffolds were more hydrophilic than PCU-g-gelatin scaffolds. Because hydrophilic PEGMA and gelatin were grafted and immobilized onto the surface, the PCU-g-PEGMA-g-gelatin scaffolds showed low platelet adhesion, perfect anti-hemolytic activity and excellent cell growth and proliferation capacity. It could be envisioned that PCU-g-PEGMA-g-gelatin scaffolds might have potential applications in tissue engineering artificial scaffolds. PMID:25746263

  10. Platelet adhesiveness in diabetes mellitus

    PubMed Central

    Shaw, S.; Pegrum, G. D.; Wolff, Sylvia; Ashton, W. L.

    1967-01-01

    Platelet adhesiveness has been assessed on whole blood from a series of 34 diabetics and 50 control subjects using adenosine diphosphate (A.D.P.) and by adherence to glass microspherules (ballotini). Using both techniques it was possible to demonstrate a significant increase in platelet adhesiveness in the diabetic patients. PMID:5614070