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  • 1
    ISSN: 0887-624X
    Keywords: grafting ; basic functionalization ; free radical polymerization ; methacrylate ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The grafting of 2-(dimethylamino)ethyl methacrylate (DMAEMA) onto two model hydrocarbons, squalane and n-eicosane, and to linear low density polyethylene (LLDPE) has been investigated. The results of the study indicate that a high reaction temperature, 160°C, and a low concentration of monomer, less than 0.3 M, are optimum conditions for the grafting reaction. Reaction products, which consisted of grafted hydrocarbons and poly(DMAEMA), were separated by solvent extraction and vacuum distillation; samples were then analyzed by NMR and FTIR spectroscopy and size exclusion chromatography. 1H-NMR spectroscopy indicates that grafted squalane contained approximately 6 DMAEMA units per squalane residue. 1H- and 13C-NMR and molecular weight studies strongly suggest that the grafts onto the model hydrocarbons consist of single DMAEMA units. Results of the melt grafting of DMAEMA onto LLDPE show that the grafting efficiency and degree of grafting are substantially lower than were expected from the model system. © 1994 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
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  • 2
    ISSN: 0887-624X
    Keywords: free radicals ; grafting ; kinetics ; methacrylate ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of grafting a basic monomer, 2-(dimethylamino)-ethyl methacrylate (DMAEMA) to hydrocarbon substrates have been investigated. These systems were chosen as models for the grafting of a homopolymerizable monomer to polyolefins such as polyethylene. The reactions with squalane and n-eicosane were initiated by an organic peroxide, 2,5-dimethyl 2,5 dit-butylperoxy)-3-hexyne; grafting yields become significant at high reaction temperatures and low monomer concentrations. In squalane, the order of reaction with respect to monomer increased from about 1.1 for 0.22-0.44M DMAEMA to almost 2 at 0.69M DMAEMA; the order with respect to initiator was 0.56. The overall activation energy in the 130-160°C temperature range was, however, surprisingly low, 42±5 kJ mol-1. When analytical data were used to separate the overall rate into those for grafting and homopolymerization, different kinetic paths were observed for the competing reactions. These results are interpreted in terms of two different mechanisms; intramolecular chain transfer plays an important role in grafting, while depropagation becomes a major factor in homopolymerization at temperatures above 150°C. © 1995 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
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  • 3
    ISSN: 0887-624X
    Keywords: reactivity ; amines ; functional polymers ; anhydride ; carbonxylic acid ; crosslink ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactive melt processing of different types of diamines with polyethylene containing carboxylic acid groups and polystyrene containing anhydride groups was carried out. The reactivity of primary, secondary, and tertiary diamines with these acid polymers was determined using various techniques. Molecular weight increases due to crosslinking were observed through (1) changes in the torque during the reactive processing, (2) decrease in melt flow indices, and (3) decrease in solubility of the reaction products. The chemical compositions of the reaction products were examined by Fourier transform infrared (FTIR) spectroscopy. Thermal analysis using differential scanning calorimetry (DSC) was carried out to determine the crystallization behavior, glass transition temperatures, and thermal stabilities of the reaction products. Results show that the primary amine is the most reactive towards carboxylic acid or anhydride groups followed by the secondary and then the tertiary amine. Anhydride groups on polymers are of higher activity towards secondary or primary amino groups than carboxylic acid groups in the nucleophilic acyl substitution reactions. Reaction products crosslinked with the primary diamine are less stable than their parent acidic polymers. On the other hand, crosslinking with the secondary or tertiary diamine gives products with higher thermal stability than the parent acidic polymers. The formation of reversible and irreversible crosslinks with different types of diamines is also reported. © 1992 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 4
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    ISSN: 0449-2986
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Propellants, Explosives, Pyrotechnics 7 (1982), S. 139-147 
    ISSN: 0721-3115
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Using especially modified torque and capillary extrusion rheometers the rheological behaviour of a typical triple-base gun propellant has been examined as a function of such processing variables as temperature, solvent content, time taken to incorporate, filler content and filler shape. Propellant doughs flow according to the law \documentclass{article}\pagestyle{empty}\begin{document}$ \sigma -\sigma _0 = {\rm K}\dot \gamma ^{\rm n} $\end{document} where σ is the shear stress applied to the dough to maintain a shear rate of γ, σ0 is the yield stress at which flow commences, K is the consistency index and n is the flow behaviour index. Variations in these constants as a function of the above mentioned variables are presented and their implications discussed. Resultant changes in the physical properties of the dried extruded propellant also are monitored.
    Additional Material: 15 Ill.
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  • 7
    ISSN: 0721-3115
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Propellant cords have been manufactured from nitrocellulose/nitroglycerin (50/50) pastes containing different types of nitrocellulose. The cords were manufactured using a solvent wet process involving incorporation and extrusion in the highly instrumented propellants processing facility at Waltham Abbey. It has been shown that the biological source from which the nitrocellulose is manufactured (wood or cotton) has a significant influence upon the dough rheology, cord diameter, shear heating and ultimate tensile strength of the dried cords. Additionally, the influence of extrusion rate upon the above parameters has been highlighted. This work compliments that previously undertaken upon the influence of nitrocellulose molecular weight on the properties of propellant doughs and dried cords.
    Additional Material: 7 Ill.
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  • 8
    ISSN: 0721-3115
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The state of the art relative to the measurement of shock and detonation pressures of the magnitude generaled by condensed high explosives is reviewed. Carbon resistors have been shown to provide a relatively inexpensive and direct method for such measurements, provided adequate calibration data are available. The gauge is fabricated by heat-sealing the carbon resistor (470 Ω, 0.125 W) into a suitable plastic material such as polystyrene; when subjected to a strong shock wave, the gauge undergoes compression and the conductivity increases in proprtion to the magnitude of the pressure. The present investigation was concerned with the experimental derivation of calibration equations relating the pressure (in gigapascal) as a function of the conductivity change ΔG (in siemens). The point of inflaction occurring at approximately 2.36 GPa, corresponding to 0.02082 S, is in agreement with previous observations in the literature. Additional experiments are being planned to resolve a problem concerning oscillatory ringing in the gauge voltage records.
    Additional Material: 4 Ill.
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  • 9
    ISSN: 0449-2951
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Allene has been polymerized to a high molecular weight by several transition metal salts reduced by aluminum triisobutyl. The polymer contained three types of unsaturation: vinylidene, vinyl, and cis; no trans unsaturation was found. A hypothesized mechanism accounted for these facts by two competitive rates: reaction of a linear intermediate with monomer to form again the linear intermediate plus one vinylidene unit, and isomerization of the linear intermediate to a cyclic intermediate which ultimately yielded one vinylidene and one vinyl or cis unit after reaction with monomer. Thus, the ratio of the two rates was controlled by the concentration of allene. The suggested mechanism proved to predict accurately the effect of the conditions of polymerization upon the structures of the resulting polymers. The nature of the transition metal also proved of importance in determining the path of polymerization as did temperature, solvent, degree of agitation, and copolymerization. Polyallene was found to exist in three crystalline forms as well as an amorphous form.
    Additional Material: 4 Ill.
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  • 10
    ISSN: 0721-3115
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An estimate of the detonation pressure of carbohydrate-metal composite explosives has been obtained experimentally by use of carbon resistor pressure gauges mounted in the wall of the confining tubes. The composite explosives were formulated from a pharmaceutical mixture of 10/90 nitroglyccrin/ß-lactose by weight, and was rendered detonable by inclusion of flaked aluminum and both flaked aluminum and ammonium perchlorate. The detonation pressure of the nitroglyccrin/ß-lactose mixture with 10 percent aluminum by weight was approximatcly 1.1 GPa. The incorporation of 30 percent ball-milled ammonium perchlorate to this formnlation increased the detonation pressure to 12.2 GPa. These pressures must be considered as estimates of the true detonation pressure, because of (a) the suspected non-ideality of the detonation state of these explosives, (b) the statistical nature of the response of the gauges, and (c) possible inconsistencies in the interpreatation of the gauge records. It is recommended that a number of gauges be used in a given experiment, and the results be averaged as one means of cireumventing the above difficulties.
    Additional Material: 3 Ill.
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