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  • 1
    Electronic Resource
    Electronic Resource
    Photo-aza-Claisen rearrangements of cyclic enaminones (1989)
    s.l. : American Chemical Society
    The @journal of organic chemistry 54 (1989), S. 4165-4168 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo00278a033
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  • 2
    Electronic Resource
    Electronic Resource
    Conductive polyethylene-carbon black composites by elongational-flow injection molding Part 3. Study of the structure and morphology (1989)
    Springer
    Colloid & polymer science 267 (1989), S. 409-413 
    Details
    ISSN: 1435-1536
    Keywords: Polyethylene-carbon black composities ; injection-molding ; electron microscopy ; small angle x-rax diffraction ; morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The morphology and structure of high molecular weight linear polyethylene (M w 450000) filled with carbon black and processed using molds that introduce an elongational flow component during injection molding has been examined using electron microscopy and x-ray diffraction techniques. The study of fracture surfaces reveals the display of shish-kebabs oriented along the injection direction with segregated longitudinal channels of carbon black particles. Molecular and lamellar changes in orientation are, furthermore, studied across the thickness of the moldings. It is shown that addition of carbon black particles to injection-molded polyethylene induces significant changes in lamellar orientation. Thus, while lamellar overgrowth proceeds perpendicular to the fiber axes within carbon free channels, lamellae grow randomly within carbon-enriched regions where flow is less pronounced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01410185
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  • 3
    Electronic Resource
    Electronic Resource
    Conductive PE-carbon black composites by elongational flow injection moulding (1988)
    Springer
    Journal of materials science 23 (1988), S. 4121-4126 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A study of the distribution of electrical conductivity in elongational-flow injection-moulded high-density polyethylene materials containing carbon black is reported. Radial and axial conductivity profiles are discussed in terms of molecular orientation variations across the bars. It is shown that for low and intermediate molecular weight matrices the conductivity decreases after material orientation through injection moulding. For high molecular weight polyethylene, as demonstrated in Part 1 of this report, conductivity increases with orientation. The results are qualitatively explained in terms of three principal effects: (i) orientation of particle aggregates during injection moulding, (ii) degradation of the aggregates depending on molecular weight, and (iii) flow-induced segregation of additive particles. The variation of the percolation threshold for the composites is additionally discussed for isotropic and injection-moulded materials in terms of factors affecting the mixing efficiency between filler and molten polymer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01106846
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  • 4
    Electronic Resource
    Electronic Resource
    Conductive PE-carbon composites by elongation flow injection moulding (1988)
    Springer
    Journal of materials science 23 (1988), S. 475-480 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In Part 1 and Part 2 of this paper the preparation of linear polyethylene (PE)-carbon black processed composites with conducting electrical properties was examined by means of elongation flow injection moulding. Mould geometry was optimized in the form of oriented double-armed bars so as to give enhanced mechanical properties combined with a high degree of electrical homogeneity. The present paper deals with composites using a high molecular weight PE matrix. It is shown that the injection-moulded composite material exhibits not only a lower percolation threshold, φc, than the conventionally pressure-moulded isotropic sample, but also conductivities two to three orders of magnitude larger than the latter. The radial and axial conductivity profiles, for concentrations well above φc, are discussed in the light of the molecular orientation variations across the bars as determined by birefringence. A segregation of primary filler particles, during flow-induced orientation, into axial channels has been shown to explain the enhancement of conductivity detected in the injected mouldings. In addition, for filler concentrations near 7%, σ-profile analysis indicates the development of a uniform conductive-stiff inner cylinder, several millimetres wide, homogeneously extending along the full length of the injected material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01174672
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  • 5
    Electronic Resource
    Electronic Resource
    Properties of elongational flow injection moulded polyethylene (1989)
    Springer
    Journal of materials science 24 (1989), S. 2643-2652 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In Parts 1 and 2 of this series the influence of mould geometry and processing parameters was investigated for elongational flow injection moulded polyethylene with the aim of improving the mechanical properties. In the present study (Part 3) injection moulding of commercial polyethylene samples has been carried out using a wide range of molecular weights. Two moulds were used, one of them only providing shear flow, the other one allowing, in addition large elongational flow. In the case of the mould with large elongational flow, at a critical molecular weight, which depends on the melt temperature, a well defined transition in birefringence and mechanical properties of the injection mouldings has been detected. This transition has been discussed in terms of a development of a percolating network structure of long-lived stable knots yielding high mechanical strength oriented mouldings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01174539
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  • 6
    Electronic Resource
    Electronic Resource
    Electrical conductivity of polyethylene-carbon-fibre composites mixed with carbon black (1988)
    Springer
    Journal of materials science 23 (1988), S. 1411-1415 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The study of electrical conductivity of high-density polyethylene-carbon-fibre composites mixed with different concentrations of carbon black is reported. The influence of the mixing procedure of the additives and material preparation is examined with regard to the conductivity values. The use of these two filler types in polyethylene composites combines the conducting features of both. Thus, while fibres provide charge transport over large distances (several millimetres), carbon black particles improve the interfibre contacts. Results are discussed with reference to simple electrical models. It is shown that for composites in which the segregated carbon black-polyethylene component lies above the percolation threshold the electrical interfibre contacts are activated through carbon black particle bridges, leading to a conductivity rise. This effect is more relevant in the case of shorter fibres. Processing of the material involving fibre orientation, such as in injection-moulding, decreases drastically the conductivity level reached.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01154609
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  • 7
    Electronic Resource
    Electronic Resource
    Time optimal left to right construction of position trees (1987)
    Springer
    Acta informatica 24 (1987), S. 461-474 
    Details
    ISSN: 1432-0525
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Summary In the following paper we are presenting a new algorithm for the on-line construction of position trees. Reading a given input string from left to right we are generating its position tree with the aid of the general concept of infix trees. An additional chain structure within the trees, called tail node connection, enables us to construct the tree within the best possible time (proportional to the number of nodes).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00292114
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  • 8
    Electronic Resource
    Electronic Resource
    Properties of elongational flow injection-molded polyethylene. Part 1: Influence of mold geometry (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 186-192 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Injection molding of polyethylene was carried out using molds that introduce axial elongational flow during the filling process, As compared with conventional injection-molding methods, the present technique yields polyethylene materials having higher mechanical strengths (σ ≈ 150 MPa). The σ-value of the moldings can be systematically monitored by adequately varying the elongational flow through modification of the mold geometry. Geometrical features of the volume containing the melt before injection as well as geometry of the die, the extruder, and the inlet influence the overall elongational flow, and thus, the mechanical strength of the moldings.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760290306
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  • 9
    Electronic Resource
    Electronic Resource
    Properties of elongational flow injection-molded polyethylene part 2: Influence of processing parameters (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 193-201 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In the first part of this series, the influence of mold geometry was examined with reference to the improvement of the mechanical properties of elongational flow injection-molded polyethylene. In the present study (Part 2), processing parameters have been investigated and the physical properties of the moldings examined. It is confirmed that mainly two parameters, the temperature of the melt and the pressure on the solidifying mold, govern the injection process. Results are discussed in terms of the molecular orientation that is developed during the filling process and depends on the temperature of the melt. The application of high pressures leads to a pressure-induced crystallization effect that freezes in the molecular orientation within the mold.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760290307
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