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  • Polymer and Materials Science  (3,277)
  • Organic Chemistry  (824)
  • Chemical Engineering  (418)
  • 1995-1999  (4,519)
  • 1980-1984
  • 1970-1974
  • 1997  (4,519)
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  • 1995-1999  (4,519)
  • 1980-1984
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  • 1
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 3745-3753 
    ISSN: 0887-624X
    Keywords: poly(urethane-imide) ; polyurethane ; polyimide ; poly(amide acid) ; oligo(amide acid) ; polyurethane prepolymer ; elastomer ; polymer network ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A polymer blend consisting of polyimide (PI) and polyurethane (PU) was prepared by means of a novel approach. PU prepolymer was prepared by the reaction of polyester polyol and 2,4-tolylenediisocyanate (2,4-TDI) and then end-capped with phenol. Poly(amide acid) was prepared from pyromellitic dianhydride (PMDA) and oxydianiline (ODA). A series of oligo(amide acid)s were also prepared by controlling the molar ratio of PMDA and ODA. The PU prepolymer and poly(amide acid) or oligo(amide acid) solution were blended at room temperature in various weight ratios. The cast films were obtained from the blend solution and treated at various temperatures. With the increase of polyurethane component, the films changed from plastic to brittle and then to elastic. The poly(urethane-imide) elastomers showed excellent mechanical properties and moderate thermal stability. The elongation of films with elasticity was more than 300%. The elongation set after the breaking of films was small. From the dynamic mechanical analysis, all the samples showed a glass transition temperature (Tg) at ca. -15°C, corresponding to Tg of the urethane component, suggesting that phase separation occurred between the two polymer components, irrespective of polyimide content. TGA and DSC studies indicated that the thermal degradation of poly(urethane-imide) was in the temperature range 250-270°C. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3745-3753, 1997
    Additional Material: 10 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 28 (1997), S. 417-423 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Determination of Deformation-induced Residual Stresses in Full Forward Extrusion and Comparison to Experimental ResultsThe macroscopic residual stresses induced by cold forward extrusion of rods are calculated by the finite element method. For an experimental determination of the residual stresses X-ray diffraction and neutron diffraction as well as the hole drilling method are applied. The results of the experiments and the calculations are in qualitative agreement, those of the experiments even are in good quantitative agreement. They allow the investigation of the influence of the processing parameters. Thus, a product optimisation with respect to residual stresses is enabled.
    Notes: Die beim Fließpressen erzeugten Eigenspannungen I. Art werden durch eine Simulation des Umformprozesses mit der Finite-Elemente-Methode berechnet. Zur experimentellen Bestimmung der Eigenspannungen werden die Röntgenbeugung, die Neutronen-beugung und das Bohrlochverfahren eingesetzt. Die Ergebnisse der Simulation und der Versuche stimmen qualitativ, die experimentellen Verfahren untereinander auch quantitativ überein. Sie ermöglichen es, den Einfluß der Variation unterschiedlicher Umformparameter auf den Eigenspannungszustand aufzuzeigen. Damit sind die Voraussetzungen für eine Erzeugnisoptimierung hinsichtlich des Eigenspannungszustandes gegeben.
    Additional Material: 14 Ill.
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  • 3
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 7 Ill.
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  • 4
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A high molecular weight, linear aromatic poly(ether ketone ether ketone ketone) (PEKEKK) has been synthesized by electrophilic Friedel-Crafts acylation condensation of 1,4-diphenoxybenzophenone with terephthaloyl chloride. The syntheses were performed as precipitation polycondensations, and the polyketones were obtained in particle form. The viscosity (molecular weight), shape and size of these particles were found to be strongly dependent on the reaction conditions. For low monomer concentration, highly ordered needle-like particles were also obtained. The chemical structure of the polymers obtained was confirmed by 1H and 13C NMR spectroscopy, and para-substitution in aryl fragments of the main chain was identified. Analysis of the expanded 1H NMR spectra for the ring proton resonances reveals defect meta- and ortho-structures. The amount and isomer ratio of these defect structures depend on the monomer concentration used.
    Additional Material: 5 Ill.
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  • 5
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Syntheses of aromatic polyketones in the form of particles were performed using a very small monomer concentration (0.05 mol/1) by the precipitation polycondensation method. Some of these particles present highly ordered elongated needle-like structures (whiskers) particularly for the all-para polyketone samples. The use of isophthaloyl instead of terephthaloyl for the same low monomer concentration produces, in addition to the globular particles, bundles of ribbon-like structures. The average size of the needle-like particles is 1-5 μm in width and 150-250 μm in length. The factors controlling the morphology texture and size of the whiskers and ribbons are shown to be the polymer structure and the reaction conditions. Formation mechanisms are discussed.
    Additional Material: 6 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Process Safety Progress 16 (1997), S. 231-236 
    ISSN: 1066-8527
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A numerical simulation of the convection process in a thermally unstable solid storage container has been carried out. The obtained results show that natural convection shifts the thermal ignition to higher induction times. Beyond a critical Rayleigh number, natural convection can prevent the system against thermal ignition. Temperature and velocity fields are calculated. The influence of the dependence of Biot numbers on temperature and the radius/height ratios on the induction times for thermal ignition has been also examined.
    Additional Material: 6 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 252 (1997), S. 257-267 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermal oxidative stability of 100 μm sulfur vulcanized latex film stretched to various extent was studied by means of the chemiluminescence technique in 130-160°C temperature interval. In the 130-150°C temperature region the induction period of oxidation increases with deformation, reaches a limiting value at about 60-70% and remains unchanged up to 200%. This effect becomes less pronounced as temperature rises from 130 to 150°C and at 160°C no change in the induction period with the extent of deformation is observed. The oxidation rate constant exhibited different behavior. It was constant in the entire region of deformations studied at 130°C, while a slight increase at extensions exceeding 100% was noticed at higher temperatures. Original sample exhibited a substantially reversible deformation at ambient conditions even when stretched 200% for 1 hour. On the other hand, preliminary 200% stretching for 30 min under nitrogen at 150°C led to 67% residual deformation at room temperature. The latter sample was found to be essentially less stable than the unstretched material. Surprisingly enough, 100% elongation imposed on the sample with residual deformation resulted in the improvement in stability which was primarily due to the rise in the induction period value. The activation energy of oxidation was 62.8 kJ/mol for unstrained and about 12.6 kJ/mol less for all strained samples.
    Additional Material: 8 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 1775-1785 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reaction of the potassium salt of acrylic acid with the potassium salt of a dicarboxylic acid and 1,4-dibromobutane was applied to the synthesis of three series of acrylate-terminated copolyesters: poly(tetramethylene maleate-co-tetramethylene phthalate) (BMPA), poly(tetramethylene fumarate-co-tetramethylenephthalate) (BFPA) and poly(tetramethylene phthalate-co-tetramethylene succinate) (BPSA). The monofunctional monomer, the potassium salt of acrylic acid, was used for the introduction of double bonds at the end of the chains and for the regulation of the molecular weight of the polyesters. The telechelic copolyesters were characterized by 1H and 13C NMR spectroscopy, in almost all cases providing an acrylate functionality of two.
    Additional Material: 5 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1589-1592 
    ISSN: 0887-6266
    Keywords: poly(tetrahydrofurfuryl acrylate) ; poly(2-ethylbutyl acrylate) ; characteristic ratio ; glass transition temperature ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis, characteristic ratio C∞ and glass transition temperature (Tg) of poly(tetrahydrofurfuryl acrylate) (PTHFA) and of poly(2-ethylbutyl acrylate) (P2EBA) are reported. P2EBA has slightly lower flexibility (C∞ = 9.2) than PTHFA (C∞ = 8.6), mainly because of the higher bulkiness of its side group and the closer proximity to the main chain. The C∞ results compared with the corresponding polymethacrylates show an increase in flexibility due to the absence of the α-methyl group. Comparison with poly(methyl acrylate) clearly shows the influence of the bulkiness of the side group on the chain flexibility. The lower Tg of P2EBA than that of PTHFA may be explained by the higher flexibility of the 2-ethylbutyl side group. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1589-1592, 1997
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 28 (1997), S. 82-87 
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Fatigue behaviour of a laser welded pseudoelastic NiTi alloy under bending stressesThe mechanical fatigue of small specimens of a commercial pseudoelastic NiTi alloy produced by laser welding and laser cutting was investigated in strain-controlled bending tests. In comparison with the base material the butt welded specimens showed significantly reduced numbers of cycles to failure. This is mainly caused by higher local strains due to height reductions in the welded joints. Both the welded microstructure and the unwelded one was able to be loaded up to 107 cycles without failure if the strain amplitude remained below 1%.
    Notes: Es wurde das Ermüdungsverhalten lasergeschweißter und -geschnittener Miniaturproben aus einer kommerziellen pseudoelastischen NiTi-Legierung in weggesteuerten Biegeversuchen bestimmt. Im Vergleich zum Ausgangsmaterial zeigten die mit Stumpfstoß geschweißten Proben deutlich herabgesetzte Bruchschwingspielzahlen. Die Ursache hierfür sind in erster Linie höhere örtliche Dehnungen auf Grund von Querschnittsverminderungen in den Schweißnähten. Sowohl das Schweiß- als auch das Ausgangsgefüge konnten mit 107 Schwingspielen beansprucht werden, wenn die Dehnungsamplitude unter 1% blieb.
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