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  • Articles  (42)
  • 1980-1984  (42)
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (42)
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  • Articles  (42)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 262 (1984), S. 361-365 
    ISSN: 1435-1536
    Keywords: Polyethylene ; chain defects ; diffraction profiles ; paracrystalline lattice distortions
    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 Wide angle X-ray diffraction scans of isothermally crystallized samples of polyethylene containing known levels of chain defects have been investigated. An analysis of scattering curves using a powder diffractometer is reported. The analytical deconvolution of Lorentz and Lorentz squared profiles for the PE experimental scattering curve and the standard is performed to give the pure profile for the polymer. The separate contribution of paracrystalline lattice distortions and coherently diffracting domains, in different crystallographic directions, to the broadening of the diffraction profiles is discussed in the light of the level of defects present.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 3 (1980), S. 7-12 
    ISSN: 1436-2449
    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: Summary New small angle X-ray diffraction data of a series of mostly low density PE samples isothermally crystallized from the melt are reported to discern between the existing ambiguities concerning the alternative of one or two lamellar periodicities. The ratio of X-ray spacings turns out to be dependent on the supercooling of the samples. This result together with the analysis of the 1st and 2nd diffraction peaks during and after heat treatments reveals that the two scattering maxima in the samples investigated most probably originate from the coexistence of two different lamellar periodicities.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Polymer bulletin 8 (1982), S. 369-375 
    ISSN: 1436-2449
    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: Summary The energy transfer ability of free and polymer-bound acetophenone and benzophenone has been studied. The polymeric sensitizers were prepared by acetylation or benzoylation of atactic polystyrene (¯Mn=67.000). Trans-cis isomerization of stilbene, monitored by UV-spectrophotometry, has enabled the energy transfer process to be probed. The values of the Stern-Volmer constants, determined by following this technique, indicate that the energy transfer efficiency of both ketones is higher when they are in free state than when they are polymer-bound.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1436-2449
    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: Summary The hardening of lamellar polyethylene (PE) as a consequence of a controlled chlorosulfonation treatment has been studied using the microindentation technique. The hardness of the polymer turns out to be a linear function of the density of treated PE. The rate of increase is larger for samples with higher crystallinity. This increase is related to the hardening of crystal lamellae due to the surface attachment of electron dense groups. The latter impede the slippage of crystals and substantially reduce the rate of creep of the material under the contact pressure applied.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1436-2449
    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: Summary A combined X-ray diffraction and DSC investigation of the crystalline phase in lamellar low density polyethylene after conventional chlorosulfonation treatment has been carried out. Our results indicate that the acid attack does not involve any heavy group penetration within the lattice. The location of these groups at the basal crystal surface contributes, however, to an enhancement of the melting temperature of the modified lamellae. It turns out that the destruction level of crystalline material at 45°C, after 15–20 h is of the order of 20% and progressively increases for longer periods of time.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 3 (1984), S. 1093-1094 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 3 (1984), S. 693-694 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 261 (1983), S. 412-416 
    ISSN: 1435-1536
    Keywords: Lamellar structure ; low density polyethylene ; chlorosulfonation ; small angle X-ray diffraction ; electronmicroscopy
    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 investigation of representative details in the lamellar microstructure of LDPE observed after controlled chlorosulfonation using both EM and SAXD is reported. For this purpose melt crystallized PE with two branch contents (ε=0.28 and 2.53 branches per 102CH2) has been prepared using Kanig's technique over a range of temperatures and treatment times. During the first treatment hours the selective incorporation of electron-dense atoms at the lamellar surface produces a macroscopic weight increase, swelling of the sample and a concurrent decrease of the SAXS intensity. The main result, however, is that the thickness of the lamellar structure does not vary with treatment time. After long chlorosulfonation times a saturation of electron-dense atoms within the surface layer and a reduction in the lateral dimensions of the lamellae take place. Optimum conditions for revealing the representative morphology are such as to lead to a weight increase of 50% for PE withε=0.28 of branches and only to an increase of 10% for material of branch content represented by anε value of 2.53.
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  • 9
    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 local deformation of the lamellar microstructure of isothermally melted crystallized unoriented polyethylene has been investigated using microindentation hardness (MH). The polymer can be visualized as a composite material consisting of hard and weak elements. The former, the lamellae, are considered to consist of mosaic blocks with liquid-like lattice distortions (paracrystallites). The latter are the interlamellar “amorphous” regions and the mosaic block lateral grain boundaries. The deformation mechanisms beneath the indenter are discussed in the light of current models of plastic deformation. MH is shown to depend on the packing density of the macromolecules in both phases and, as a result, it can be clearly correlated with the macroscopic density of the material. The unit cell expansion and lattice distortions increase in parallel as a consequence of increasing incorporation of chain defects within the lattice. This provokes a conspicuous decrease in the microhardness of the crystals. The increase in lattice distortions is consistent with the concurrent decrease of lamellar thickness and, hence, of the coherently diffracting lattice volume. These results unambiguously emphasize the physical significance of the mosaic block character of the lamellae in determining the micromechanical properties of the material. Finally it is shown that the strain boundary which defines the zone of crystal destruction under the indenter also depends on the average volume of the paracrystallites and on the volume fraction of crystalline material.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 16 (1981), S. 2831-2836 
    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 Experiments carried out on pultruded fibre reinforced polyester resins show that, at moderate fibre volume fractions, the compressive strength of aligned fibre composites depends linearly on the volume fraction. The strength falls off when the fibre volume fraction,V f=0.4 with Kevlar and high strength carbon fibres. The effective fibre strength atV f〈0.4 is much less than the tensile strength but it is close to the tensile strength with E-glass fibres and high modulus carbon fibres. Poor adhesion between fibres and matrix reduces the compressive strength, as does kinking the fibres when the fibre radius of curvature is reduced to below 5 mm. Misalignment of the fibres reduces the compressive strength when the average angle of misalignment exceeds about 10° for glass and carbon fibres. However, with Kevlar no such reduction is observed because the compression strength of Kevlar reinforced resin is only a very little better than that of the unreinforced resin.
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