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  • Chemistry  (18)
  • stainless steel  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 517-522 
    ISSN: 1573-4846
    Keywords: ormocer ; coatings ; chemical protection ; stainless steel ; PMMA-ZrO2 ; corrosion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The chemical protection of 316 L stainless steel coated with ORMOCER coatings of polymethylmethacrylate (PMMA) and ZrO2 has been verified. The coatings were dip-coated on the substrates from sols prepared by mixing zirconium propoxide (ZrOC3H7)4, isopropanol (C3H7OH), glacial acetic acid (CH3COOH), polymethylmethacrylate and water under application of ultrasounds. The films were heat treated between 40 and 300°C in air up to 20 h. Their morphology was studied by electron scanning microscopy (SEM). Their anticorrosion behavior was analysed in 0.5M-H2SO4 solutions through potentiodynamic polarization curves at room temperature.The influence of the sol preparation, coating composition as well as of the duration and temperature of heat treatments on the corrosion parameters is reported. The films act as geometric blocking layers against the corrosive media and increase the lifetime of the substrate up to a factor 30.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 8 (1997), S. 517-522 
    ISSN: 1573-4846
    Keywords: ormocer ; coatings ; chemical protection ; stainless steel ; PMMA-ZrO2 ; corrosion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The chemical protection of 316 L stainless steel coated with ORMOCER coatings of polymethylmethacrylate (PMMA) and ZrO2 has been verified. The coatings were dip-coated on the substrates from sols prepared by mixing zirconium propoxide (ZrOC3H7)4, isopropanol (C3H7OH), glacial acetic acid (CH3COOH), polymethylmethacrylate and water under application of ultrasounds. The films were heat treated between 40 and 300°C in air up to 20 h. Their morphology was studied by electron scanning microscopy (SEM). Their anticorrosion behavior was analysed in 0.5M-H2SO4 solutions through potentiodynamic polarization curves at room temperature. The influence of the sol preparation, coating composition as well as of the duration and temperature of heat treatments on the corrosion parameters is reported. The films act as geometric blocking layers against the corrosive media and increase the lifetime of the substrate up to a factor 30.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of sol gel science and technology 1 (1994), S. 177-184 
    ISSN: 1573-4846
    Keywords: sol-gel coatings ; chemical protection ; stainless steel ; ZrO2 ; corrosion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract ZrO2 coatings deposited on 316 L stainless steel sheets were synthesized by sol-gel method using Zr(OC3H7)4 as precursor and isopropanol, glacial acetic acid, and water as solvents for application with ultrasounds. Different solutions for dip-coating were prepared with compositions varying between 0.025 and 0.9 mol/dm3 of ZrO2. X-ray diffraction shows that the films densified at 800°C are crystalline with a tetragonal structure. The thickness of the coatings varied from 0.35–0.75 μm. The influence of the ZrO2 coatings on the corrosion behavior of stainless steel substrates in aqueous NaCl was studied through potentiodynamic polarization curves at 1 mV/s. The values of the electrochemical parameters allow for an explanation of the role of the films in the increased resistance of steel against corrosion in moderately aggressive environments.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 193 (1992), S. 2445-2451 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: New methacrylic copolymers with prospective second-order nonlinear optical effects are synthesized by radical copolymerization of methyl methacrylate with conjugated zwitterionic methacrylate monomers (2,6-di-tert-butyl-4-[1-(ω-methacryloyloxyalkyl)-4-pyridino]phenolates,1a and 1b). These monomers are obtained via a multi-step reaction. First, 4-(3,5-di-tert-butyl-4-hydroxyphenyl)pyridine (2) is electrosynthesized by an SRN1 reaction in liquid ammonia. Then, this pyridine derivative is N-alkylated by an ω-bromoalkyl methacrylate (5a or 5b) which, in its turn, is obtained by esterification of an ω-bromoalcohol and methacryloyl chloride.
    Additional Material: 2 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 998-1003 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Transesterification may be used to crosslink a copolymer such as ethylene vinyl acetate with poly(ethylene acrylate-co-propylene) in the presence of dibutyltin oxide as a catalyst. A rheological study of the mechanism of this exchange reaction has been made: The kinetics of the crosslinking reaction was determined by studying the time and temperature dependence of the dynamic storage modulus G′(t, T)ω. Kinetic curves obtained for different reactive blends (EVA, PP/EVA, and PPf/EVA) allowed for the evaluation of the activation energy of the reaction and, thus, specified the appropriate parameters (temperature and time) for carrying out this reaction in a molten state.
    Additional Material: 9 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 34 (1994), S. 1011-1015 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The transesterification reaction catalyzed by dibutyltin oxide has been used to crosslink miscible blends (at about 200°C) of ethylene vinyl acetate (EVA) and ethylene methyl acrylate (EMA) copolymers. Then, microwave heating at 2.45 GHz with the fundamental TE01 mode was used for activation of this crosslinking reaction. The microwave treatment was carried out in a continuous process through a resonant cavity on line with a twin screw extruder equipped with a strip die or a circular die, which imposed the shape of the samples in the waveguide. Therefore, a shape factor due to the geometry of the samples and their orientation with respect to the electromagnetic field was defined. Last, this technique was applied to the microwave crosslinking of an EVA/EMA blend dispersed in a polypropylene matrix and consequently offers a new route to control the morphology of the polymer blends.
    Additional Material: 6 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 35 (1995), S. 518-527 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Using an integral nonlinear constitutive equation including the Log-Normal relaxation spectrum, the fiber-spinning behavior of commercial polypropylenes is studied. The relaxation spectrum is strongly related to the molecular weight distribution. Moreover, by means of a finite element analysis, simulated stress and velocity profiles are obtained either in isothermal or nonisothermal cases. In the isothermal case, broadening the relaxation spectrum leads to more pronounced curvature of the velocity profile. In the nonisothermal case, the critical draw ratio is sensitive to the mean relaxation time which depends on both average molecular weight and distribution breadth. It is shown that increasing the average relaxation time leads to a less rapid growth of the velocity. Furthermore, this effect is less pronounced when the relaxation spectrum is wider.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The linear viscoelastic behavior of commercial broad-distribution polypropylenes is studied. The samples underwent different controlled peroxide degradation rates, so they exhibit different molecular distributions. The relaxation spectrum is obtained by assuming that it takes the shape of a Log-Normal distribution. It is in agreement with the linear viscoelasticity theory by providing limiting values, contrary to other models. Moreover, the ratio τw/τn which takes place in this law is very useful to distinguish the synthesis differences of the samples when the Melt Flow Index alone cannot.
    Additional Material: 4 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 47 (1975), S. 61-77 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: When the ozonisation of bulk or suspension poly(vinylchloride) is carried out in tetrachloroethane solution between 0-120°C the molecular weight decreases continuously and the rate of breaking of chains deduced from the intrinsic viscosity variation is constant under isothermal conditions. Whatever the time and temperature of ozonisation may be, at every breaking, β and α chlorinated acid groups are introduced which have been characterized by infrared spectroscopy, high resolution NMR spectroscopy and potentiometric titration in dimethylformamide. Besides these functions, peroxide groups have also been identified and their concentration has been determined for different times and temperatures of ozonisation.This study permits to propose two mechanisms to explain the breaking of chains. The first implies the previous dehydrochlorination of the polymer and the second the formation of unstable peroxides which by decomposition cause the breaking of chains.
    Notes: Quelle que soit la nature du polychlorure de vinyle (masse ou suspension) l'action de l'ozone en milieu homogène dans le tétrachloroéthane provoque la décroissance continue de la masse moléculaire dans le domaine de température 0-120°C et la vitesse de coupure des chaînes déduite des variations de viscosité est constante en conditions isothermes.Quels que soient le temps et la température d'ozonisation, à chaque point de coupure apparaissent des fonctions acides α et β chlorées qui ont été caractérisées par spectroscopie infra-rouge, RMN haute résolution et dosage potentiométrique en milieu diméthylformamide. Outre ces fonctions, des peroxydes ont égé également identifiés dans le polymère et on a suivi leur concentration en fonction des conditions d'ozonisation.Cette étude permet de proposer deux mécanismes pour expliquer la coupure des chaînes, l'un suppose une déhydrochloruration préalable du polymère et l'autre la formation de peroxydes instables qui en se décomposant provoqueraient la coupure des chaînes.
    Additional Material: 9 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 25 (1987), S. 423-433 
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Iodine complexes of six monosubstituted polyacetylenes with methyl, ethyl, propyl, pentyl, t-butyl, and phenyl substituents have been characterized by electronic spectroscopy. UV spectra allow the determination of the nature and the amount of active species, and photoelectronic spectra confirm the nature of these species. These measurements indicate the presence of iodine in the I3- and I2 forms. The concentration of I3- is low (0.12-4.0 mol%), and it depends on the nature of the substitutent, but this amount does not decrease when the films are left under vacuum. On the other hand, the adsorption of ε high concentration of iodine is possible; this adsorption is governed by a diffusion mechanism and is reversible. Iodine doping leads to a cis-to-trans isomerization of the polymers, except for poly(3-3-dimethyl-1-butyne), which can be isomerized to the cis or to the trans form, depending on the solvent employed. Electrical properties of polymer I3- complexes are also reported. Conductivities of about 10-4 Ω-1 cm-1 are obtained for all polymers in the presence of an excess of iodine.
    Additional Material: 5 Ill.
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