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  • Polymer and Materials Science  (11)
  • Dynamics, dynamical systems, lattice effects
  • fiscal deficit
  • Aircraft Propulsion and Power
  • 1995-1999  (11)
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  • 1
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 1219-1227 
    ISSN: 0887-624X
    Schlagwort(e): 1,2,4-benzenetricarboxylic acid monoesters ; poly(amide-imide) structural regularity ; poly(amide-imide) “one-pot” synthesis ; 13C-NMR spectra of poly(amide-imide) ; phosphorylation reaction ; Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Aromatic processable poly(amide-imide)s have been prepared according to the Yamazaki and Higashi phosphorylation reaction from flexible aromatic diamines and a mixture of isomeric 1,2,4-benzenetricarboxylic acid monoethylesters following a novel “one-pot” procedure. The polymerization was performed in 1-methyl-2-pyrrolidone/LiCl solutions using triphenylphosphite and pyridine as condensing agents to form amide bonds. Cyclization of the intermediate poly(amide-amic ethylester) occurred by eliminating ethanol under the polymerization conditions used, thus leading to the formation of imide rings. The influence of several parameters which regulate the degree of polymerization and the formation of the imide rings, such as reaction temperature, triphenylphosphite/monomers molar ratio, and pyridine concentration was carefully investigated. In particular, the catalytic activity of pyridine in the imidization reaction has been demonstrated. 13C-NMR spectroscopy has been used to show the absence of constitutional regularity in the prepared PAIs thus indicating equal reactivity toward polycondensation of the two different carboxyl groups of the 1,2,4-benzenetricarboxylic acid monoethylesters. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    ISSN: 0935-9648
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    ISSN: 0935-9648
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 227 (1995), S. 43-55 
    ISSN: 0003-3146
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Beschreibung / Inhaltsverzeichnis: Die Kinetik der Vulkanisation sowie die Vernetzungsdichte von Styrol-Butadien-Kautschukmischungen wurden mit zwei Vulkanisationssystemen, einem wirksamen (EV) und einem konventionellen (CV), untersucht. Ein oberflächenmodifiziertes Silikat mit Boramingruppen (Si—O—B—(NH2)2) wurde als Füllstoff eingesetzt. Unbehandeltes und mit zwei Silanen (γ-Mercaptopropyl-trimethoxysilan und γ-Aminopropyl-triethoxysilan) modifiziertes Silikat wurden zum Vergleich eingesetzt. Die bestenkinetischen Parameter, wie die höchste Vulkanisierungsgeschwindigkeit, die längste Induktionszeit und die kleinste Aktivierungsenergie, wurden für die Mischung mit boraminiertem Silikat erhalten. Die Vernetzungsdichte, die mit dieser Mischung erreicht wurde, ist ähnlich der von mit Silan modifiziertem Silikat erzielten, da wahrscheinlich die Boramingruppen auf der Silikatoberfläche besser verteilt sind. Diese Fakten führen zu wichtigen technologischen Verbesserungen: größere Verarbeitungssicherheit, schnellere Vulkanisierungsgeschwindigkeit und verbesserte physikalische Eigenschaften.
    Notizen: Vulcanization kinetics and crosslink density of styrene-butadiene rubber compounds have been studied with two vulcanization systems, an efficient (EV) and a conventional (CV) one. A surface-modified silica with boron-amine groups (Si—O—B—(NH2)2) was employed as filler. Untreated and modified silica with two silanes (γ-mercaptopropyl-trimethoxysilane and γ-aminopropyl-triethoxysilane) have been used as reference.The best kinetic parameters, such as highest vulcanization rate, longest induction time and lowest activation energy, were obtained for the compound with boronaminated silica. The crosslink density, achieved with this compound, is similar to that with silane-modified silica, probably because of the better surface distribution of boron-amine groups on the silica. These facts lead to important technological improvements: better processing safety, faster vulcanization rate and improved physical properties.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 17 (1996), S. 461-469 
    ISSN: 1022-1336
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The homopolymerization of styrene and its copolymerization with ethylene in the presence of a vanadium-based supported catalyst, {VCI3, 1 AICI3}, associated to triethylaluminium is examined. As indicated by means of 13C nuclear magnetic resoance and differential scanning calorimetry analysis, the homopolystyrenes obtained present a highly isotactic microstructure and are semicrystalline (melting temperature 220°C).In the case of styrene/ethylene random copolymerization, the formation of both, polyethylene blocks and isotactic polystyrene sequences was identified by analysis of the crude polymer. Solubility characteristics and structural characteristics from nuclear magnetic resonance spectra of these products support the formation of copolymers with ethylene and isotactic styrene blocks rather than that of two distinct homopolymers.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 196 (1995), S. 3833-3844 
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The effect and the role of halogenated molecules as additives for supported vanadium catalytic systems has been investigated both in high temperature ethylene homopolymerization and in its copolymerization with 1-hexene. Addition of CH3CCI3 to the {VCl3, xAICI3} or {VCl3, xCrCI3} system, leads to a strong productivity improvement. The intensity of the activating effect depends on the nature of the support. Results suggest that the activation involves both oxidation of V(II) deactivated species into potentially active trivalent ones, and generation of new active sites. Studies on the structure of ethylene/1-hexene copolymers show that the addition of halocarbons leads to copolymers with a higher comonomer content (SCB) and a better homogeneity in composition.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 1691-1699 
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The characteristic ratios of three samples of poly(1-hexadecene) with different tacticities were evaluated from intrinsic viscosity and molecular weight data obtained with a size exclusion chromatograph with dual (concentration plus viscosity) detector. No significant differences were found for the characteristic ratio in the studied range of tacticities. Theoretical calculations for the unperturbed dimensions were also performed for these samples by using the rotational isomeric state model, and compared with the experimental results.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    ISSN: 1022-1336
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Composition profiles generated by interdiffusion in the concentrated regime between poly(phenylene oxide)-polystyrene (PPO-PS) blend pairs are experimentally determined by two techniques. Three-point bending moment measurements over a convenient temperature range (DMA (dynamic mechanical analysis) method) are used to determine interphase composition profiles. Confocal micro-Raman spectroscopy is also used to measure local compositions along a direction which is perpendicular to the original interface. The study includes some limiting cases, to test accuracy, precision and flexibility of the “DMA method”. Excellent agreement is found between results obtained by both independent methods.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    ISSN: 1022-1352
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Multiring diamines and diacids containing ether and isopropylidene or hexafluoroisopropylidene bridges between phenyl groups were used alone or together with 1,4-phenylenediamine and terephthalic acid to prepare flexible or semirigid aromatic polyamides by direct polycondensation using triphenyl phosphite and pyridine as condensing agents. All the polyamides are readily soluble in N,N-dimethylacetamide, N-methyl-2-pyrrolidone and N,N-dimethylformamide. The wholly flexible polyamides are completely amorphous whereas those prepared from 1,4-phenylenediamine or terephthalic acid are partially crystalline and melt in the temperature range from 276 to 330°C. Thermal analysis shows Tg's in the range from 204 to 216°C for the wholly flexible polyamides and in the range from 239 to 257°C for the semirigid ones. Both classes of aromatic polyamides show excellent thermal resistance which is comparable with that of rigid-rod aramides.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 55 (1995), S. 233-246 
    ISSN: 0021-8995
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The crystallization kinetics of a polyetheretherketone (PEEK)/liquid crystalline polymer (LCP) blend was studied by using differential scanning calorimetry. Nonisothermal runnings were performed on heating and on cooling at different rates. Isothermal crystallization experiments at 315, 312, 310, and 307°C, from the melt state (380°C) were performed in order to calculate the Avrami parameters n and k and the fold surface free energy, σe. Polarized light optical micrographs were also obtained to confirm the Avrami predictions. It was observed that the LCP retarded the PEEK crystallization process and that the PEEK melting temperature decreased with the amount of LCP, but the LCP melting temperature increased with the amount of PEEK. Probably the PEEK improves the perfection of the LCP crystalline domains. A spherulitic morphology in pure PEEK and its blends was predicted by the Avrami analysis; however this morphology was only observed for pure PEEK and for the 80/20 composition. The other compositions presented a droplet and fibrillar-like morphology. The overall crystallization rate was observed to decrease with the crystallization temperature for all compositions. Finally, σe was found to decrease with the increase of LCP in the blends, having unrealistic negative values. Thus, calculations were made assuming σe constant at all compositions. It was observed that δ, the interfacial lateral free energy, decreased but still remained positive. It was concluded that in these blends neither σe nor σ could be considered constant. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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