Urethane

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Andreas Lendlein - One of the best experts on this subject based on the ideXlab platform.

  • Atomistic simulation of the shape-memory effect in dry and water swollen poly[( rac-lactide)-co-glycolide] and copolyester Urethanes thereof
    Macromolecular Chemistry and Physics, 2014
    Co-Authors: Ehsan Ghobadi, Karl Kratz, Moritz Heuchel, Andreas Lendlein
    Abstract:

    An atomistic molecular dynamics simulation approach is applied to model the influence of Urethane linker units as well as the addition of water molecules on the simulated shapememory properties of poly [( rac -lactide)- co -glycolide] (PLGA) and PLGA-based copolyester Urethanes comprising different Urethane linkers. The shape-memory performance of these amorphous packing models is explored in a simulated heating-deformation-cooling-heating procedure. Depending on the type of incorporated Urethane linker, the mechanical properties of the dry copolyester Urethanes are found to be significantly improved compared with PLGA, which can be attributed to the number of intermolecular hydrogen bonds between the Urethane units. Good shape-memory properties are observed for all the modeled systems. In the dry state, the shape fixation is found to be improved by implementation of Urethane units. After swelling of the copolymer models with water, which results in a reduction of their glass transition temperatures, the relaxation kinetics during unloading and shape recovery are found to be substantially accelerated. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pai Lung Chou - One of the best experts on this subject based on the ideXlab platform.

  • Photodiscoloration inhibition of wood coated with UV-curable acrylic clear coatings and its elucidation
    Polymer Degradation and Stability, 2000
    Co-Authors: Shang Tzen Chang, Pai Lung Chou
    Abstract:

    Wood coated with Urethane-modified acrylic coatings was susceptible to yellowing induced by light. To find out the mechanism for inhibiting its photodiscoloration, wood specimens covered with separate acrylic clear free films containing stabilizers were used to simulate coated wood. Ultraviolet light absorbers tested in this study reduced not only the discoloration of coating films but also those of the underlying wood. HALS was not helpful in reducing the photodiscoloration of wood coated with aromatic Urethane-modified acrylate containing light absorbers, but it showed a significant synergistic effect on the inhibition of photodiscoloration of wood coated with aliphatic Urethane-modified acrylate containing light absorbers. Comparisons of the UV transmission spectra of coating films revealed that HALS preserved the absorption capability of the light absorber in aliphatic Urethane-modified acrylate after the lightfastness test, therefore elongating the service life of light absorber and, consequently, that of the coating.

Timothy S Blackwell - One of the best experts on this subject based on the ideXlab platform.

  • epithelial nf κb activation promotes Urethane induced lung carcinogenesis
    Proceedings of the National Academy of Sciences of the United States of America, 2007
    Co-Authors: Georgios T Stathopoulos, Taylor P Sherrill, Dongsheng Cheng, Robert M Scoggins, Vasiliy V Polosukhin, Linda Connelly, Fiona E Yull, Barbara Fingleton, Timothy S Blackwell
    Abstract:

    Chronic inflammation is linked to carcinogenesis in several organ systems. In the lungs, NF-κB, a central effector of inflammatory responses, is frequently activated in non-small-cell lung cancer, but its role in tumor promotion has not been studied. Several lines of evidence indicate that ethyl carbamate (Urethane)-induced lung tumor formation, a prototypical mouse model of multistage lung carcinogenesis, is potentiated by inflammation. We found that mouse strains susceptible to lung tumor formation (FVB, BALB/c) exhibited early NF-κB activation and inflammation in the lungs after Urethane treatment. However, a resistant strain (C57B6) failed to activate NF-κB or induce lung inflammation. In FVB mice, we identified Urethane-induced NF-κB activation in airway epithelium, as well as type II alveolar epithelial cells and macrophages. Using an inducible transgenic mouse model (FVB strain) to express a dominant inhibitor of NF-κB specifically in airway epithelial cells, we found that Urethane-induced lung inflammation was blocked and tumor formation was reduced by >50%. Selective NF-κB inhibition resulted in increased apoptosis of airway epithelial cells at 2 weeks after Urethane treatment in association with a marked reduction of Bcl-2 expression. These studies indicate that NF-κB signaling in airway epithelium is integral to tumorigenesis in the Urethane model and identify the NF-κB pathway as a potential target for chemoprevention of lung cancer.

Ehsan Ghobadi - One of the best experts on this subject based on the ideXlab platform.

  • Atomistic simulation of the shape-memory effect in dry and water swollen poly[( rac-lactide)-co-glycolide] and copolyester Urethanes thereof
    Macromolecular Chemistry and Physics, 2014
    Co-Authors: Ehsan Ghobadi, Karl Kratz, Moritz Heuchel, Andreas Lendlein
    Abstract:

    An atomistic molecular dynamics simulation approach is applied to model the influence of Urethane linker units as well as the addition of water molecules on the simulated shapememory properties of poly [( rac -lactide)- co -glycolide] (PLGA) and PLGA-based copolyester Urethanes comprising different Urethane linkers. The shape-memory performance of these amorphous packing models is explored in a simulated heating-deformation-cooling-heating procedure. Depending on the type of incorporated Urethane linker, the mechanical properties of the dry copolyester Urethanes are found to be significantly improved compared with PLGA, which can be attributed to the number of intermolecular hydrogen bonds between the Urethane units. Good shape-memory properties are observed for all the modeled systems. In the dry state, the shape fixation is found to be improved by implementation of Urethane units. After swelling of the copolymer models with water, which results in a reduction of their glass transition temperatures, the relaxation kinetics during unloading and shape recovery are found to be substantially accelerated. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Jukka V. Seppälä - One of the best experts on this subject based on the ideXlab platform.

  • Synthesis and characterization of a biodegradable thermoplastic poly(ester-Urethane) elastomer
    Macromolecules, 1997
    Co-Authors: Janne Kylmä, Jukka V. Seppälä
    Abstract:

    Thermoplastic poly(ester-Urethanes) were polymerized in a two-step process: a condensation copolymerization of lactic acid (LA) and -caprolactone (CL), using stannous octoate as catalyst, followed by an increase in the molecular weight through Urethane linking. The use of 1,4-butanediol results in oligomer molecules with hydroxyl functionality at both ends. The effect of comonomer ratio on the thermal and mechanical properties of the poly(ester-Urethane) was investigated. SEC, FTIR, and 13CNMRwere used to confirm the formation and structure of the polymer; a random sequence distribution of the comonomer units was concluded along the polymeric chains. All poly(ester-Urethanes) were amorphous, with Tg varying from 53 to -45 °C. Poly(ester-Urethanes) with a small amount of CL units were rigid, having a tensile modulus of 1700-2100 MPa, maximum stress of 36-47 MPa, and maximum strain of 4-7%. CL-rich poly(ester-Urethanes) were highly elastomeric with maximum stress of 9 MPa and with maximum strain over 1000%. Hydrolytic degradation was studied in phosphate buffer solution (pH 7.4) at 37 °C.