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  • 1
    ISSN: 0947-5117
    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: The ductility loss of the highly corrosion resistant alloy NiMo28 (Alloy B-2) during manufacturing of components for chemical plants and precautions to prevent itVortrag anläßlich der Achema '91, Frankfurt/Main, 09.-15. Juni 1991; überarbeitete und ergänzte Fassung.Alloy B-2 exhibits an excellent corrosion resistance in reducing media, especially in a wide range of concentration and temperature of hydrochloric acid and sulphuric acid. In spite of its almost binary constitution and therefore simple phase equilibria the alloy revealed in the past difficulties in workability, creating considerable problems when the alloy had to be manufactured into components for chemical plants. This is caused by formation of the intermetallic phase Ni4Mo which is an ordered phase of the Ni-rich solid solution.The susceptibility to the ductility loss of the alloy NiMo28 (alloy B-2) has been evaluated by time-temperature-impact strength diagrams. Furthermore, the positive effect of adjustments of the alloy composition (Fe and Cr) within the limits of the actual standards on the workability is pointed out. The influence of a 5% cold forming operation on the ductility loss is demonstrated, too. Recommendations for manufacturing of the alloy are given in order to avoid detrimental internal stresses by an additional heat treatment.
    Notes: Die Legierung NiMo28 zeichnet sich durch ihre herausragende Korrosionsbeständigkeit unter reduzierenden Bedingungen aus. Sie ist speziell beständig gegen Salzsäure in weiten Konzentrations-und Temperaturbereichen und in Schwefelsäure. Trotz ihrer quasibinären Konstitution und damit übersichtlich darstellbaren Phasengleichgewichte erwies sich die Legierung in der Vergangenheit für den Chemie-Apparatebau als schwierig in der Verarbeitung. Ursache dafür ist das Auftreten der intermetallischen Phase Ni4Mo, die eine Ordnungsphase des nickelreichen Mischkristalls ist. Anhand von Zeit-Temperatur-Kerbschlagarbeits-Diagrammen wird die Versprödungsneigung des Werkstoffs NiMo28 (2.1617) erläutert. Darüber hinaus wird aufgezeigt, welch positiven Effekt das Zulegieren von Eisen und Chrom innerhalb der durch die Normen vorgegebenen zulässigen Grenzen auf das Verarbeitungsverhalten hat. Abschließend erfolgt die Darstellung des Einflusses einer 5%igen Kaltverformung auf die Versprödungsneigung. Dem Weiterverarbeiter im Chemie-Apparatebau werden Empfehlungen gegeben, wann und wie durch eine zusätzliche Lösungsglühung die Ni4Mo-Ordnungsphase aufgelöst werden kann, um nachteilige Eigenspannungen abzubauen.
    Additional Material: 12 Ill.
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  • 2
    ISSN: 0173-2803
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
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  • 3
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 6 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 55 (1983), S. 58-59 
    ISSN: 0009-286X
    Keywords: Absorption ; Gasreinigung ; Elektrochemie ; Festbettelektrode ; Chlor ; Schwefeldioxid ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
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  • 5
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The aliphatic polyamides polyamide-6 (1), and polyamide-6,6 (2), the aromatic polyamides of terephthalic acid with different diamines [p-phenylenediamine, (3), 4,4′-biphenylylenediamine, (4), 4,4′-oxydianiline, (5)] as well as polyimides of pyromellitic acid with aliphatic diamines [ethylenediamine, (6), hexamethylenediamine, (7)] and aromatic diamines [4,4′-biphenylylenediamine, (8), 4,4′-methylenedianiline, (9), 4,4′-isopropylenedianiline, (10), 4,4′-oxydianiline, (11)] were pyrolyzed at temperatures between 800 K and 1073 K within the vacuum of the high temperature inlet system of a field ion mass spectrometer. Amines, amides, imides and nitriles are characteristic fragments of the thermal degradation. The degradation mechanisms which are determined by structure and amount of the thermal decomposition products, are described.
    Notes: Die aliphatischen Polyamide Polyamid-6 (1), Polyamid-6,6 (2) und die aromatischen Polyamide der Terephthalsäure mit verschiedenen Diaminen [p-Phenylendiamin, (3), 4,4′-Biphenylylendiamin, (4), 4,4′-Oxydianilin, (5)] sowie Polyimide der Pyromellitsäure mit aliphatischen Diaminen [Äthylendiamin, (6), Hexamethylendiamin, (7)] und aromatischen Diaminen [4,4′-Biphenylylendiamin, (8), 4,4′-Methylendianilin, (9), 4,4′-Isopropylidendianilin, (10), 4,4′-Oxydianilin, (11)] wurden bei Temperaturen zwischen 800 K und 1073 K im Vakuum des Hochtemperatureinlaßsystems eines Massenspektrometers pyrolysiert und durch Feldionenmassenspektrometrie untersucht. Amine, Amide, Imide und Nitrile sind charakteristische Fragmente des thermischen Abbaus. Die Abbaumechanismen, welche durch Struktur und Ausbeute der thermischen Zersetzungsprodukte bestimmt sind, werden beschrieben.
    Additional Material: 11 Ill.
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  • 6
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Linear-temperature controlled pyrolysis with subsequent analysis of the pyrolyzates (volatiles and residue) by 18 V electron-impact mass spectrometry (EIMS) and FTIR spectrometry, respectively, yields optimal informations on the thermal degradation mechanisms of heat-resistant polymers. In the present paper results with aromatic polyesters are reported. Poly(4-oxybenzoyl) firstly (675 K) releases residual educt (acetoxybenzoic acid), solvent (hexahydroterphenyl), phenol and oligomers. In the temperature range of maximum decomposition (Tmax = 815 K) several consecutive processes take place. At 760 K, “monomer” (oxybenzoyl) and two series of oligomers with different endgroups are set free. At 815 K, formation of phenol, and at 845 K. formation of diphenyl ether are the dominating process. The maxima of CO2 and CO release are at 790 K and 825 K, respectively. In the residue, diaryl ketone, 9-fluorenone and phenolic structures were observed. Mechanisms including Fries-analogue rearrangements are discussed. A typical poly-(4-oxybenzoyl-ran-2-oxy-6-naphthoyl) (“Vectra A 950”) with 73 mol-% oxybenzoyl units produced, during the “evaporation phase” (640 K) and in addition to oxybenzoyl “monomer” and oligomers, oxynaphthoyl and a series of hetero-fragments containing one oxynaphthoyl unit and one or two oxybenzoyl units. At 785 K (close to Tmax), the formation of phenol, CO2, CO and oxybenzoyl was predominant. In the residue, the formation of diaryl ketone, dibenzofuran and 9-fluorenone structures was observed. Mechanisms are discussed in analogy to the degradation of poly(4-oxybenzoyl).
    Additional Material: 16 Ill.
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  • 7
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Pyro-field ion mass spectrometry was used to study the primary fragments as well as the depolymerization behaviour of some α-methylstyrene (α-MS) copolymers. α-MS-methyl methacrylate (MMA) copolymers, when pyrolyzed, decompose mainly into the two monomers. The zip-depolymerization usually proceeds through the whole chain, disregarding the hetero-links between different monomeric units. Hetero-fragments are formed only with a small probability; still lower is the concentration of homo-dimers in the pyrolysate.Primary fragments of poly(acrylonitrile) (PAN) are acrylonitrile (AN), (AN)2, (AN)3, HCN, C3H5CN, C4H7CN, C5H9CN and higher nitriles. During pyrolysis of α-MS-AN copolymers, α-MS sequences zipdepolymerize with formation of the monomer. This retropolymerization stops at heterolinks, and fragments of the type α-MS-AN or α-MS-(AN)2 are formed. Long AN sequences in the copolymer cause, as PAN itself, formation of AN oligomeres as well as higher alkene cyanides. Isolated AN units lead to the formation of monomeric AN.
    Notes: Die Pyro-Feldionenmassenspektrometrie wurde zur Untersuchung der Primärfragmente und des Abbauverhaltens von α-Methylstyrol(α-MS)-Copolymeren eingesetzt. α-MS-Methylmethacrylat(MMA)-Copolymere depolymerisieren pyrolytisch unter weitgehender Rückbildung der beiden Monomeren. Die Retropolymerisation („Reißverschlußmechanismus„) geht meist über die Verknüpfungsstellen verschiedener Monomerer hinweg. Heterofragmente (α-MS-MMA) werden nur mit einer geringen Wahrscheinlichkeit gebildet; noch geringer ist die Konzentration von Homodimeren im Pyrolysat.Primärfragmente des Polyacrylnitrils (PAN) sind Acrylnitril (AN), (AN)2, (AN)3, HCN, C3H5CN, C4H7CN, C5H9CN und höhere Nitrile. Bei der Pyrolyse von α-MS-AN-Copolymeren retropolymerisieren α-MS-Sequenzen unter Rückbildung des Monomeren. Die Retropolymerisation macht an Heteroverknüpfungsstellen halt; hierbei bilden sich Heterofragmente des Typs α-MS-AN oder α-MS-(AN)2. Längere AN-Sequenzen im Copolymeren führen bei der Pyrolyse wie bei PAN zu AN-Oligomeren sowie zu höheren Alkencyaniden. Isolierte AN-Einheiten führen zur Bildung von monomerem AN.
    Additional Material: 7 Ill.
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  • 8
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Polyäther Poly(oxy-1,3-phenylen) (1), Poly(oxy-2,6-dimethyl-1,4-phenylen) (2), Poly(oxy-2-methyl-6-phenyl-1,4-phenylen) (3), Poly(oxy-2,6-diphenyl-1,4-phenylen) (4) und Poly(oxy-2,5-dimethoxy-1,4-phenylen) (5) wurden bei Temperaturen zwischen 563 K und 853 K im Direkteinlaß eines Massenspektrometers pyrolysiert. Die charakteristische Verteilung von monomeren und oligomeren Fragmenten zeigt, daß es sich um statistische Kettenspaltung handelt. Der Kettenspaltung, die primär zu Radikalen führt, folgen schnelle Stabilisierungsreaktionen, so daß hauptsächlich Fragmente mit Hydroxy- und Phenyl-Endgruppen in den Pyro-Feldionenmassenspektren (PFIMS) gefunden werden. Bei 2 und 3 werden durch das Sauerstoffatom in ortho-Stellung die Bindungen zwischen den Methylseitengruppen und den Phenylenringen der Hauptkette gelockert. Bei einer Spaltung der Hauptkette zwischen zwei Grundbausteinen kann eine der Spaltungsstelle benachbarte Methylgruppe des einen Bruchstücks zum entstandenen freien Ende des anderen übertragen werden. Auf diese Weise können sowohl Fragmente mit fehlender als auch solche mit zusätzlicher Methylgruppe gebildet werden. Während die Methoxygruppen in 5 relativ leicht abgespalten werden, verbleiben die Phenyl-Seitengruppen der Polyäther 3 und 4 überwiegend an den Phenylenringen der Hauptkette.
    Notes: The polyethers poly(oxy-1,3-phenylene) (1), poly(oxy-2,6-dimethyl-1,4-phenylene) (2), poly(oxy-2-methyl-6-phenyl-1,4-phenylene) (3), poly(oxy-2,6-diphenyl-1,4-phenylene) (4), and poly(oxy-2,5-dimethoxy-1,4-phenylene) (5) were pyrolyzed in the direct inlet system of a mass spectrometer at temperatures between 563 K and 853 K. Statistical chain splitting is confirmed by the characteristic distribution of the thermal degradation products, namely monomers and oligomers. Chain splitting, leading primarily to radicals, is followed by fast stabilization reactions. Therefore, the pyro-field ion mass spectra (PFIMS) show mainly fragments with hydroxy and phenyl end groups. In the polyethers 2 and 3, the oxygen atom in ortho position lowers the strength of the bonds between the methyl side groups and the phenylene rings of the backbone. On fragmentation between monomeric units, one of the methyl groups at the point of chain break has the chance to change place to the newly established free end of the other fragment. In this way, fragments with both lack and surplus of a methyl group will be obtained. While the methoxy groups of 5 are easily split off, the overwhelming majority of the phenyl side groups in the polyethers 3 and 4 remain at the phenylene rings of the main chain.
    Additional Material: 7 Ill.
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