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  • 1
    Electronic Resource
    Electronic Resource
    Magneto-gravitational equilibrium in galactic disks: observational evidence for conserved primordial magnetic fields in galaxies - AApS 13/4 (1993) 385-390
    Amsterdam : Elsevier
    Chinese Astronomy and Astrophysics 18 (1994), S. 125 
    Details
    ISSN: 0275-1062
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0275-1062(94)90085-X
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of urethanes on base-catalyzed epoxy reaction (1995)
    Springer
    Journal of polymer research 2 (1995), S. 115-120 
    Details
    ISSN: 1572-8935
    Keywords: Aryl-connected carbamate (Ar-carbamate) ; Alkyl-connected carbamate (Al-carbamate) ; Epoxide group ; Tertiary amine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The effect of carbamate (urethane) groups on the curing reaction of an epoxy catalyzed by tertiary amine was studied by infrared (IR) and differential scanning calorimetry (DSC) analysis. It was found that the aromatic-connected carbamate (Ar-carbamate) accelerated the consumption rate of epoxy in the epoxy/tertiary amine/Ar-carbamate reaction system, where the tertiary amine and Ar-carbamate was found to form an active complex with stoichiometric ratio in the curing reaction. However, under the introduction of aliphatic-connected carbamate (Al-carbamate) into the reaction system, no complex formed with the tertiary amine during the reaction and therefore no acceleration in the reaction rate was observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01493211
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  • 3
    Electronic Resource
    Electronic Resource
    A possible association of a long-period pulsar with a supernova remnant? (1996)
    Springer
    Astrophysics and space science 243 (1996), S. 371-377 
    Details
    ISSN: 1572-946X
    Keywords: Pulsar ; Supernova Remnant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this paper we argue that the PSR B 1849+00 and SNR G33.6+0.1 are possibly associated, because (1) there is only a small probability of chance superposition in this sky region; (2) although the estimates of the distance and the age of the two objects contain a high degree of uncertainty, they are not inconsistent; (3) the implied transverse velocity of the pulsar is also quite reasonable according to the measured distribution of pulsar velocities. The association could be verified by measuring the proper motion of PSR B 1849+00, which is estimated to be about 10 mas·yr−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00644707
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  • 4
    Electronic Resource
    Electronic Resource
    Polyurethane-crosslinked epoxy resins. I. Mechanical behavior (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 182 (1990), S. 193-203 
    Details
    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: Polyurethanpräpolymere (PU) auf der Basis von Poly(butylenadipaten) (PBA) bzw. Poly(oxytetramethylen) polyolen (PTMO) wurden als Vernetzer für Bisphenol-A-diglycidylether (DGEBA) eingesetzt. Anschließend wurde DGEBA mit einem tertiären Amin zu einem PU-vernetzten DGEBA ausgehärtet. Die Reißfestigkeit sowohl von PU(PBA)-als auch von PU(PTMO)-vernetzten Systemen stieg mit steigendem PU-Gehalt bis zu einem Maximum an, um bei noch höheren Gehalten von PU wieder abzufallen. Hinsichtlich der Izod-Schlagzähigkeit brachte die Vernetzung des DGEBA mit PU(PBA) eine wesentlich bedeutendere Verbesserung als mit PU(PTMO). Andererseits zeigten PU(PTMO)-vernetzte DGEBA-Polymere viel höhere Werte der Bruchenergie G1 C als PU(PBA)-vernetzte.
    Notes: Polyurethane (PU) prepolymers based on poly(butylene adipate) (PBA) and poly(oxytetramethylene) (PTMO) polyols were employed as a crosslinking agent to the diglycidyl ether of bisphenol A (DGEBA). Then the DGEBA was cured with a tertiary amine catalyst to form PU-crosslinked DGEBA.The tensile strength of both the PU(PBA)-crosslinked DGEBA and PU(PTMO)-crosslinked DGEBA systems increased to a maximum value with increasing PU content in the system and then decreased with further increasing PU content.Izod impact property of these PU-crosslinked DGEBA indicated that the PU(PBA)-crosslinked DGEBA had much more significant improvement than the PU(PTMO)-crosslinked DGEBA. On the contrary, the fracture energy (G1 C value) of the resultant PU-crosslinked DGEBA showed that the PU(PTMO)-crosslinked DGEBA had much higher G1 C values than the PU(PBA)-crosslinked DGEBA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1990.051820114
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  • 5
    Electronic Resource
    Electronic Resource
    Interpenetrating polymer networks of polyurethane and furfuryl alcohol, IIa. Processability and properties of pultruded fiber-reinforced composites (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 218 (1994), S. 41-52 
    Details
    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: Die Herstellung von faserverstärkten interpenetrierenden Netzwerken (IPN) aus Polyurethan (PU) und Furfurylalkohol (FA) mittels Pultrusion wurde untersucht. Wie Viskositätsmessungen zeigen, nimmt die Topfzeit der PU/FA-IPN-Präpolymeren mit steigendem PU-Gehalt zu, und die Reaktivität ist hoch bei höheren Temperaturen. Aus morphologischen Untersuchungen geht hervor, daß mit steigendem PU-Gehalt die Benetzung der Fasern mit den PU/FA-Harzen verbessert wird. Die bei Zugversuchen erhaltenen Bruchflächen der glasfaserverstärkten PU/FA-IPNs mit PU-Gehalten unter 15 phr zeigen sogenannte “hackle patterns”. Die Zugfestigkeit der pultrudierten PU/FA-IPN-Composite ist bei einem PU-Gehalt von 5 phr am höchsten; Biegefestig-keit, Biegemodul und Wärmeformbeständigkeit nehmen jedoch mit zunehmendem PU-Gehalt ab. Die mechanischen Eigenschaften der mit Glas-, Carbon- oder Aramid- fasern (Kevlar 49) verstärkten pultrudierten Composite nahmen mit steigendem Volumenanteil der Fasern zu.
    Notes: A feasibility study of pultrusion of fiber-reinforced polyurethane/furfuryl alcohol (PU/FA) interpenetrating polymer/network IPN composites has been made. From the viscosity study, it was found that the pot life of the PU/FA IPN prepolymers increased with PU content and showed high reactivity at elevated temperature. It was confirmed from the morphological study that the wetting of fibers by the PU/FA IPN resins was improved with PU content. The appearance of the tensile failure surfaces of the pultruded glass fiber-reinforced PU/FA IPN composites showed “hackle patterns” for PU contents below 15 phr. The mechanical property study shows that the tensile strength of pultruded PU/FA IPN composites is the highest when the PU content is 5 phr. However, the flexural strength, flexural modulus and HDT decreased with PU content. The mechanical properties of various fiber-reinforced (glass, carbon, and Kevlar 49 aramid fiber) pultruded PU/FA IPN composites increased with fiber volume content.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052180104
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  • 6
    Electronic Resource
    Electronic Resource
    Polyurethane-crosslinked epoxy resins. II. Compatibility and morphologyPart 1: cf. Angew. Makromol. Chem. 182 (1990) 193 (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 184 (1991), S. 89-97 
    Details
    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: Polyurethan(PU)-vernetzte Bisphenol-A-diglycidylether (DGEBA) wurden durch Reaktion der sekundären Hydroxygruppe im DGEBA-Präpolymeren mit den im PU-Präpolymeren vorhandenen freien Isocyanatendgruppen hergestellt. Obwohl das PU als Vernetzer für das DGEBA wirkte, fanden sich in der Morphologie und im dynamisch mechanischen Verhalten je nach Typ und Molekulargewicht der eingesetzten Polyole Unterschiede. Es gab keine signifikante Verschiebung der Lage des Maximums des Verlustmoduls (E′″) zwischen den Polyester-und den Polyether-vernetzten DGEBA-Polymertypen, aber die Intensität des E″-Peaks stieg mit der Verwendung des Polyesterpräpolymeren an. Die Morphologie dieser Polyester-PU-vernetzten DGEBA-Polymeren war homogen einphasig, während die Polyether-PU-Typen eine Zweiphasenmorphologie mit PU-Teilchen, dispergiert in der DGEBA-Matrix zeigten.
    Notes: The polyurethane(PU)-crosslinked diglycidyl ether of bisphenol A (DGEBA) was prepared from the reaction of the pendent secondary hydroxy group in DGEBA with the isocyanate-terminated group present in the PU prepolymer. Though the PU acted as a crosslinking agent for the DGEBA, the morphology and dynamic mechanical behaviour of these PU-crosslinked DGEBA could be different among themselves depending on the type and molecular weight of polyols employed in the PU. There was no significant shift in the loss modulus (E″) peaks of the DGEBA crosslinked with the polyester-type and polyether-type polyurethanes, but the intensity of the E″ peaks increased as the polyester-type PU employed. The morphology of this polyester-type PU-crosslinked DGEBA exhibited a homogeneous one-phase system, while the DGEBA crosslinked with the polyether-type PU showed a two-phase morphology with the PU particles dispersed in DGEBA matrix.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051840108
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  • 7
    Electronic Resource
    Electronic Resource
    Interpenetrating polymer networks of polyurethane and furfuryl alcohol. I. Morphology and mechanical properties (1994)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 214 (1994), S. 39-56 
    Details
    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: Interpenetrierende Polymernetzwerke aus Polyurethan (PU) und Furfurylalkohol (FA) wurden aus Furfurylalkohol mit p-Toluolsulfonsäure als Katalysator und NCO-terminiertem Polyurethan-Prepolymerem mit m-Xylylendiamin (MXDA) als Ketten-verlängerer hergestellt. Durch IR-Analyse konnte ermittelt werden, daß im System PU/MXDA/FA die Polymerisation von PU/MXDA und die Homopolymerisation von FA als Hauptreaktionen ablaufen. Die Zugfestigkeiten der interpenetrierenden PU/FA-Netzwerke mit 5 phr PU-Anteil sind größer als die der reinen Komponenten. Die Biegefestigkeit, der Biegemodul, die Shore D-Härte und die Wärmeformbeständigkeit nehmen mit steigendem Polyurethananteil ab, während die Kerbschlagzähigkeitzunimmt. Die Verträglichkeit der Komponenten wurde mit dynamisch-mechanischer Analyse und Rasterelektronenmikroskopie untersucht. Die Komponenten in den Netzwerken sind semikompatibel, da die Glastemperaturen der IPN-Bestandteile im Vergleich zu denen der Einzelkomponenten zueinander verschoben sind. Die Ergebnisse der Rasterelektronenmikroskopie belegen, daß die Netzwerke heterogen sind.
    Notes: Polyurethane/furfuryl alcohol (PU/FA) interpenetrating polymer networks (IPNs) were synthesized from furfuryl alcohol using p-toluene sulfonic acid as a catalyst and blocked NCO-terminated PU prepolymer with m-xylylenediamine (MXDA) as a chain extender. From IR spectrum analysis it was found that the major reactions in the PU/MXDA/FA system are the polymerization of PU/MXDA and the self-polymerization of FA. The tensile strengths of PU/FA IPNs that contain 5 p.h.r. PU are greater than those of the pure components. The flexural strength, flexural modulus, Shore D hardness and HDT decrease and the notched Izod impact strength increases with the polyurethane content. The compatibility of the compounds in these PU/FA IPNs was investigated by dynamic mechanical analysis and scanning electron microscopy. It was found that glass transition temperatures are shifted inwardly which indicated that the PU/FA IPNs were semicompatible. It was confirmed from scanning electron micrography that the system was heterogeneous.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1994.052140105
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  • 8
    Electronic Resource
    Electronic Resource
    Graft interpenetrating polymer networks of polyurethane and epoxy. I. mechanical behavior (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 28 (1990), S. 623-630 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyurethanes (PU) based on poly(butylene adipate) [PU(PBA)] and poly(oxypropylene) [PU(PPG)] polyols have bean introduced into the diglycidyl ether of bisphenol A (epoxy) to form interpenetrating polymer networks (IPNs) with a PU-grafted epoxy structure (graft-IPNs).The tensile strength in both PU(PPG)/epoxy and PU(PBA)/epoxy systems increases with increasing PU content. Maximum values emerge at PU/epoxy ratios between 19/81 and 27/73. This is explained as a result of the presence of the graft structure, which leads to more intimate interpenetration between the PU and epoxy in the graft-IPNs.Dynamic mechanical analysis (DMA) indicates that the PU introduced can be incorporated in either the α or β transition domain of the epoxy. The tensile strength of the resulting graft-IPNs shows a significant improvement as the PU is incorporated in the α transition domain of the epoxy. It is also noted that suitable amounts of PU incorporated in both the α and β transition domains of epoxy can increase the tensile strength of the IPNs, while excessive amounts of PU introduced into both α or β transition domains tend to decrease the tensile strength of the graft-IPNs.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1990.090280503
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  • 9
    Electronic Resource
    Electronic Resource
    Graft interpenetrating polymer networks of polyurethane and epoxy. II. Toughening mechanism (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 28 (1990), S. 783-794 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Graft interpenetrating polymer networks (graft-IPNs) of polyurethane (PU) and the diglycidyl ether of bisphenol A (epoxy) were prepared by first grafting excess PU prepolymer to the epoxy and then simultaneously polymerizing the PU prepolymer and epoxy. The fracture properties, at high shear rate (e.g., impact) and low shear rate (e.g., pseudostatic tensile fracture energy measurement) of these graft-IPNs exhibit opposite behavior. Although dispersed rubber particles can enhance the Izod impact strength, toughening of the matrix of graft-IPNs was found to be the main contribution. In contrast, it was found that a heterogeneous morphology with suitably dispersed rubber domains of appropriate size as well as the toughness of the matrix are requirements for effectively increasing the fracture energy at low shear rate. A reinitiating crack in the plastic matrix is proposed as the main toughening mechanism and can be invoked to interpret the fracture behavior at high and low shear rates of the graft-IPNs.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1990.090280601
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  • 10
    Electronic Resource
    Electronic Resource
    Swelling equilibrium and sorption kinetics of urethane-modified bismaleimides elastomer (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1747-1755 
    Details
    ISSN: 0887-6266
    Keywords: polyurethane ; bismaleimide ; swelling ; equilibrium ; swelling kinetics ; functionality ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The swelling equilibrium and diffusion kinetics in various solvents of the maleimide-terminated polyurethanes (UBMIs) and of the triol and tetraol-crosslinked polyurethanes (PU) were studied. The polymer volume fraction of the UBMIs at swelling equilibrium is much higher than that of the tetraol-crosslinked PU networks for the same type of polyol used in the PU. It was explained by the high functionality of the UBMIs produced in the network structure. Furthermore, the molecular weight between crosslinks (Mc) has been calculated from the swelling model and the results exhibit good agreement with the proposed network structure. The early time sorption kinetic data were obtained to investigate the diffusion mechanism of the solvent in the networks. The solubility, diffusion coefficients, and permeability of the solvent in UBMI networks were found to be lower than in the multiol-crosslinked PU networks. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1747-1755, 1997
    Additional Material: 8 Ill.
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