Hydrolytic Stability

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Byungdae Park - One of the best experts on this subject based on the ideXlab platform.

  • Hydrolytic Stability and crystallinity of cured urea–formaldehyde resin adhesives with different formaldehyde/urea mole ratios
    International Journal of Adhesion and Adhesives, 2011
    Co-Authors: Byungdae Park, Howon Jeong
    Abstract:

    Abstract This study investigated the relationship between the Hydrolytic Stability and the crystalline regions of cured UF resins with different formaldehyde/urea (F/U) mole ratios to better understand the hydrolysis of cured urea–formaldehyde (UF) resin adhesives responsible for its formaldehyde emission in service. As the F/U mole ratio decreased, the Hydrolytic Stability of cured UF resins improved, but decreased when the particle size of the resin was reduced. To further understand the improved Hydrolytic Stability of cured UF resin with lower F/U mole ratios, X-ray diffraction (XRD) was extensively used to examine the crystalline part of cured UF resins, depending on F/U mole ratios, cure temperature and time, hardener type and level. Cured UF resins with higher F/U mole ratios (1.6 and 1.4) showed amorphous structure, while those with lower F/U mole ratios (1.2 and 1.0) showed crystalline regions, which could partially explain the improved Hydrolytic Stability of the cured UF resin. The crystalline part intensity increased as cure temperature, cure time and hardener content increased. But the 2 θ angles of these crystalline regions did not change, depending on cure temperature and time, hardener type and level, suggesting that the crystalline regions of the cured UF resin were inherent. This study indicates that the crystalline regions of cured UF resins with lower F/U mole ratio contribute partially to the improved Hydrolytic Stability of the cured resin.

  • Hydrolytic Stability of cured urea formaldehyde resins modified by additives
    Journal of Applied Polymer Science, 2009
    Co-Authors: Zaimatul Aqmar Abdullah, Byungdae Park
    Abstract:

    Urea-formaldehyde (UF) resins are prone to hydrolysis that results in low-moisture resistance and subsequent formaldehyde emission from UF resin-bonded wood panels. This study was conducted to investigate Hydrolytic Stability of modified UF resins as a way of lowering the formaldehyde emission of cured UF resin. Neat UF resins with three different formaldehyde/urea (F/U) mole ratios (1.4, 1.2, and 1.0) were modified, after resin synthesis, by adding four additives such as sodium hydrosulfite, sodium bisulfite, acrylamide, and polymeric 4,4′-diphenylmethane diisocyanate (pMDI). All additives were added to UF resins with three different F/U mole ratios before curing the resin. The Hydrolytic Stability of UF resins was determined by measuring the mass loss and liberated formaldehyde concentration of cured and modified UF resins after acid hydrolysis. Modified UF resins of lower F/U mole ratios of 1.0 and 1.2 showed better Hydrolytic Stability than the one of higher F/U mole ratio of 1.4, except the modified UF resins with pMDI. The Hydrolytic Stability of modified UF resins by sulfur compounds (sodium bisulfate and sodium hydrosulfite) decreased with an increase in their level. However, both acrylamide and pMDI were much more effective than two sulfur compounds in terms of Hydrolytic Stability of modified UF resins. These results indicated that modified UF resin of the F/U mole ratio of 1.2 by adding acrylamide was the most effective in improving the Hydrolytic Stability of UF resin. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

  • Hydrolytic Stability of cured urea‐formaldehyde resins modified by additives
    Journal of Applied Polymer Science, 2009
    Co-Authors: Zaimatul Aqmar Abdullah, Byungdae Park
    Abstract:

    Urea-formaldehyde (UF) resins are prone to hydrolysis that results in low-moisture resistance and subsequent formaldehyde emission from UF resin-bonded wood panels. This study was conducted to investigate Hydrolytic Stability of modified UF resins as a way of lowering the formaldehyde emission of cured UF resin. Neat UF resins with three different formaldehyde/urea (F/U) mole ratios (1.4, 1.2, and 1.0) were modified, after resin synthesis, by adding four additives such as sodium hydrosulfite, sodium bisulfite, acrylamide, and polymeric 4,4′-diphenylmethane diisocyanate (pMDI). All additives were added to UF resins with three different F/U mole ratios before curing the resin. The Hydrolytic Stability of UF resins was determined by measuring the mass loss and liberated formaldehyde concentration of cured and modified UF resins after acid hydrolysis. Modified UF resins of lower F/U mole ratios of 1.0 and 1.2 showed better Hydrolytic Stability than the one of higher F/U mole ratio of 1.4, except the modified UF resins with pMDI. The Hydrolytic Stability of modified UF resins by sulfur compounds (sodium bisulfate and sodium hydrosulfite) decreased with an increase in their level. However, both acrylamide and pMDI were much more effective than two sulfur compounds in terms of Hydrolytic Stability of modified UF resins. These results indicated that modified UF resin of the F/U mole ratio of 1.2 by adding acrylamide was the most effective in improving the Hydrolytic Stability of UF resin. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

  • effects of formaldehyde urea mole ratio and melamine content on the Hydrolytic Stability of cured urea melamine formaldehyde resin
    European Journal of Wood and Wood Products, 2009
    Co-Authors: Byungdae Park
    Abstract:

    The influence of formaldehyde/urea (F/U) mole ratio and melamine content on the Hydrolytic Stability of urea-melamine-formaldehyde (UMF) resin was investigated. The Hydrolytic Stability of cured UMF resin was determined by measuring the mass loss and the liberated formaldehyde concentration after acid hydrolysis. A higher F/U mole ratio and greater melamine content of UMF resins resulted in lower Hydrolytic Stability. These results indicated that higher F/U mole ratio and greater melamine content resulted in more branched network structure, which subsequently increases the susceptibility of cured UMF resin toward acid hydrolysis.

  • Effects of formaldehyde/urea mole ratio and melamine content on the Hydrolytic Stability of cured urea-melamine-formaldehyde resin
    European Journal of Wood and Wood Products, 2008
    Co-Authors: Byungdae Park, Sang-min Lee, Jeang-kwan Roh
    Abstract:

    The influence of formaldehyde/urea (F/U) mole ratio and melamine content on the Hydrolytic Stability of urea-melamine-formaldehyde (UMF) resin was investigated. The Hydrolytic Stability of cured UMF resin was determined by measuring the mass loss and the liberated formaldehyde concentration after acid hydrolysis. A higher F/U mole ratio and greater melamine content of UMF resins resulted in lower Hydrolytic Stability. These results indicated that higher F/U mole ratio and greater melamine content resulted in more branched network structure, which subsequently increases the susceptibility of cured UMF resin toward acid hydrolysis.

Simon M. Ametamey - One of the best experts on this subject based on the ideXlab platform.

  • organofluorosilanes as model compounds for 18f labeled silicon based pet tracers and their Hydrolytic Stability experimental data and theoretical calculations pet positron emission tomography
    Chemistry: A European Journal, 2009
    Co-Authors: Aileen Höhne, Markus Reiher, Ulrike Voigtmann, Ulrich Klar, Keith Graham, August P Schubiger, Simon M. Ametamey
    Abstract:

    Silicon chemistry has only recently been discovered by radiochemists as a straightforward tool for the introduction of 18 F into biomolecules for positron emission tomography (PET) imaging. 18 F-labeled PET tracers must be stable towards defluorination under physiological conditions, but it is known that the Hydrolytic Stability of the silicon-fluorine bond is determined by the nature of the substituents on silicon. In the presented study we performed an extensive investigation on the Hydrolytic Stability of various synthesized organofluorosilane model compounds. By means of density functional theory (DFT) methods a theoretical model of organofluorosilane hydrolysis, which correlates with the experimentally determined Hydrolytic half-lives, is developed. The calculation of the difference of Si-F bond lengths between the optimized structures of the starting material A and the intermediate structure C allows the estimation of the Hydrolytic Stability of newly designed compounds. This model permits the facilitated development of improved building blocks for the synthesis of novel 18 F-silyl-modified biomolecules for PET imaging.

  • Organofluorosilanes as Model Compounds for 18F‐Labeled Silicon‐Based PET Tracers and their Hydrolytic Stability: Experimental Data and Theoretical Calculations (PET=Positron Emission Tomography)
    Chemistry (Weinheim an der Bergstrasse Germany), 2009
    Co-Authors: Aileen Höhne, Markus Reiher, Ulrike Voigtmann, Ulrich Klar, Keith Graham, P. August Schubiger, Simon M. Ametamey
    Abstract:

    Silicon chemistry has only recently been discovered by radiochemists as a straightforward tool for the introduction of 18 F into biomolecules for positron emission tomography (PET) imaging. 18 F-labeled PET tracers must be stable towards defluorination under physiological conditions, but it is known that the Hydrolytic Stability of the silicon-fluorine bond is determined by the nature of the substituents on silicon. In the presented study we performed an extensive investigation on the Hydrolytic Stability of various synthesized organofluorosilane model compounds. By means of density functional theory (DFT) methods a theoretical model of organofluorosilane hydrolysis, which correlates with the experimentally determined Hydrolytic half-lives, is developed. The calculation of the difference of Si-F bond lengths between the optimized structures of the starting material A and the intermediate structure C allows the estimation of the Hydrolytic Stability of newly designed compounds. This model permits the facilitated development of improved building blocks for the synthesis of novel 18 F-silyl-modified biomolecules for PET imaging.

Aileen Höhne - One of the best experts on this subject based on the ideXlab platform.

  • organofluorosilanes as model compounds for 18f labeled silicon based pet tracers and their Hydrolytic Stability experimental data and theoretical calculations pet positron emission tomography
    Chemistry: A European Journal, 2009
    Co-Authors: Aileen Höhne, Markus Reiher, Ulrike Voigtmann, Ulrich Klar, Keith Graham, August P Schubiger, Simon M. Ametamey
    Abstract:

    Silicon chemistry has only recently been discovered by radiochemists as a straightforward tool for the introduction of 18 F into biomolecules for positron emission tomography (PET) imaging. 18 F-labeled PET tracers must be stable towards defluorination under physiological conditions, but it is known that the Hydrolytic Stability of the silicon-fluorine bond is determined by the nature of the substituents on silicon. In the presented study we performed an extensive investigation on the Hydrolytic Stability of various synthesized organofluorosilane model compounds. By means of density functional theory (DFT) methods a theoretical model of organofluorosilane hydrolysis, which correlates with the experimentally determined Hydrolytic half-lives, is developed. The calculation of the difference of Si-F bond lengths between the optimized structures of the starting material A and the intermediate structure C allows the estimation of the Hydrolytic Stability of newly designed compounds. This model permits the facilitated development of improved building blocks for the synthesis of novel 18 F-silyl-modified biomolecules for PET imaging.

  • Organofluorosilanes as Model Compounds for 18F‐Labeled Silicon‐Based PET Tracers and their Hydrolytic Stability: Experimental Data and Theoretical Calculations (PET=Positron Emission Tomography)
    Chemistry (Weinheim an der Bergstrasse Germany), 2009
    Co-Authors: Aileen Höhne, Markus Reiher, Ulrike Voigtmann, Ulrich Klar, Keith Graham, P. August Schubiger, Simon M. Ametamey
    Abstract:

    Silicon chemistry has only recently been discovered by radiochemists as a straightforward tool for the introduction of 18 F into biomolecules for positron emission tomography (PET) imaging. 18 F-labeled PET tracers must be stable towards defluorination under physiological conditions, but it is known that the Hydrolytic Stability of the silicon-fluorine bond is determined by the nature of the substituents on silicon. In the presented study we performed an extensive investigation on the Hydrolytic Stability of various synthesized organofluorosilane model compounds. By means of density functional theory (DFT) methods a theoretical model of organofluorosilane hydrolysis, which correlates with the experimentally determined Hydrolytic half-lives, is developed. The calculation of the difference of Si-F bond lengths between the optimized structures of the starting material A and the intermediate structure C allows the estimation of the Hydrolytic Stability of newly designed compounds. This model permits the facilitated development of improved building blocks for the synthesis of novel 18 F-silyl-modified biomolecules for PET imaging.

Silvia Gross - One of the best experts on this subject based on the ideXlab platform.

  • Hydrolytic Stability and Hydrogen Peroxide Activation of Zirconium-Based Oxoclusters: Hydrolytic Stability of Zirconium-Based Oxoclusters
    European Journal of Inorganic Chemistry, 2014
    Co-Authors: Francesco Faccioli, Matthias Bauer, Danilo Pedron, Antonio Sorarù, Mauro Carraro, Silvia Gross
    Abstract:

    The Hydrolytic Stability of [Zr6(OH)4O4{O(O)CC(CH3)=CH2}12] (Zr6), and [Zr6O4(OH)4{O(O)CCH2CH=CH2}12]2·6[CH2=CHCH2C(O)OH] (Zr12) oxoclusters in different environments was thoroughly investigated by FTIR, Raman, and X-ray photoelectron spectroscopy (XPS). Specific information about the local structures around the Zr centers during the Stability tests was achieved by in situ extended X-ray absorption fine structure (EXAFS) measurements, and the exact compositions were determined by inductively coupled plasma MS (ICP-MS) and elemental analysis. By this multidimensional spectroscopic approach, an overview on the structures formed after different treatments could be gained. The Stability of the oxoclusters was then investigated in the presence of hydrogen peroxide, and the formation of peroxo–metal complexes was detected. Thus, a kinetic study was performed in acetonitrile to evaluate the performances of the oxoclusters as oxygen transfer catalysts. The oxidation of methyl p-tolyl sulfide to the corresponding sulfoxide and sulfone was chosen as a model reaction; in some cases, an interesting selectivity towards the formation of the sulfone was found over more than 4700 catalytic cycles

John H. Wells - One of the best experts on this subject based on the ideXlab platform.

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