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  • 1
    Electronic Resource
    Electronic Resource
    Diamagnetic properties of polyethylene (1985)
    Springer
    Polymer bulletin 13 (1985), S. 379-384 
    Details
    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: Abstract A novel approach which accounts for the independent contributions to the specific diamagnetic susceptibility (χm) of the amorphous and crystalline phases in, both, the solid and the liquid state of a series of low density polyethylenes (PE) is reported. The dependence of diamagnetism, for each phase contribution, on crystallinity is derived. The much larger rate of increase found for the diamagnetic contribution of the amorphous regions to χm is in accordance with the major influence of defects, perturbing the packing of chain segments rejected from the crystals. A parallel discussion for the liquid state favours the occurrence of a local mesomorphic state above the melting point.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00262124
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  • 2
    Electronic Resource
    Electronic Resource
    Diamagnetism and structure of nitric acid-treated bulk polyethylene (1982)
    Springer
    Polymer bulletin 7 (1982), S. 317-321 
    Details
    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 An alternative procedure to examine the nature of the end product of nitric-acid-treated bulk polyethylene involving the measurement of the diamagnetic susceptibility is reported. This simple non-destructive method complements previous results obtained by means of IR spectroscopy. Thus after selectively removing the surface layer of the polyethylene lamellae with nitric acid (t 〉 50h) the diamagnetic susceptibility substantially decreases to values which are consistent with tilted paraffinic chains terminated by carboxyl groups including -NO2 groups in a 4∶1 ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00256799
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  • 3
    Electronic Resource
    Electronic Resource
    Van der Waals networks in the compressive deformation of polyethylene (1991)
    Springer
    Colloid & polymer science 269 (1991), S. 859-866 
    Details
    ISSN: 1435-1536
    Keywords: Van der Waalsnetwork ; polyethylene ; compression ; injectionmolding ; biaxialdeformation
    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 compressive stress-strain behavior of biaxially oriented polyethylene (PE), obtained by pressing uniaxially oriented samples, is described with the aid of the van der Waals equation of state. Results are discussed in terms of two parameters: the biaxiality (B) and the biaxial draw ratio (〈λ〉), which offer a measure of the strain along the two principal directions and of the average draw ratio on the film plane, respectively. Comparison of experimental and calculated data indicates that after compression up to very large deformations the maximum average strain (λ m ), which is proportional to the square root of the chain length of the network, remains constant. This result supports the view that the network of entanglements is not destroyed after compression. Experiments carried out on isotropic melt crystallized PE show the presence of a network having a not very different chain length. Finally, it is shown that the segment length of this network is close to the X-ray long period of the initial structure. This result implies the existence of a high density of entanglements (∼two entanglements every three adjacent lamellae), which are rejected into the defective layer of the crystals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00657301
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  • 4
    Electronic Resource
    Electronic Resource
    Comparative study of size and distribution of lamellar thicknesses and long periods in polyethylene with a shish-kebab structure (1996)
    Springer
    Journal of materials science 31 (1996), S. 4199-4206 
    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 This study contains a combined application of three different techniques for the study of injection moulded polyethylene (PE), showing an oriented shish-kebab structure: small angle X-ray scattering (SAXS), low frequency Raman spectroscopy (LAM) and transmission electron microscopy (TEM), A series of linear PEs and molecular weights in the range 51000–478000 has been investigated and two injection temperatures have been used (T m=144 and 210 °C). SAXS patterns from the highly oriented regions show the presence of either one axial long period (L 1) or two (L 1 and L 2) depending on molecular weight (¯M w) and T m. It is shown that L 1 and L 2 increase with ¯M w up to a given critical molecular weight ¯M c. Above ¯M c, L 1 and L 2 remain constant. Raman results qualitatively confirm the existence of two separate distributions of straight-length chain segments for those samples having molecular weights above the critical value. Shorter segments are shown to be more abundant than the longer ones. In the lowest molecular weight sample, results from SAXS, TEM and Raman spectroscopy seem to be consistent with each other, although in some cases a tilted molecular arrangement within the lamellae has to be invoked. On the other hand, in case of the highest molecular weight sample, the length of the short straight-chain segments derived from Raman spectroscopy agrees well with the double periodicity obtained from SAXS. On the contrary, long periods measured from TEM only correspond to the shorter SAXS periodicity. This result is discussed by assuming the occurrence of crystalline bridges among adjacent lamellae.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00356439
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  • 5
    Electronic Resource
    Electronic Resource
    Gelatin layers for holographic purposes: an X-ray diffraction study (1995)
    Springer
    Journal of materials science 30 (1995), S. 6145-6150 
    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 order to overcome uniformity problems in large u.v. holoconcentrators recorded in dichromated gelatin, the structure of hardened gelatin layers has been studied. X-ray diffraction patterns show that layers are formed by individual gelatin chains partly associated as triple-stranded helical rods as those found in native collagen. These rods, in turn, may form fibrillar aggregates. Helical rods and microfibrils are, to a great extent, parallel to the layer surface and their relative amount and packing depend on the hardener as well as on temperature and drying time after coating. X-ray diffraction offers the possibility of estimating in a simple manner the relative amount of triple-helical rods in crystallographic register within the gelatin layers. From these results, a method for obtaining uniform large holograms by means of a slow layer drying process is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00369660
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  • 6
    Electronic Resource
    Electronic Resource
    Physical ageing and glass transition in amorphous polymers as revealed by microhardness (1989)
    Springer
    Journal of materials science 24 (1989), S. 2934-2938 
    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 Microhardness (MH) data as a function of temperature for two amorphous polymers [poly(methylmethacrylate) and poly(vinylacetate)] and two semicrystalline polymers [poly(ethyleneterephthalate) and poly(arylether ether ketone)] quenched into the amorphous state are presented. It is shown that MH can conveniently detect the glass transition temperature (T g) for the above mentioned polymers. Molecular rearrangements taking place above and belowT g, such as physical ageing leading to a more compact molecular packing, and thermal expansion can also be followed by means of MH measurements. Finally, the presence of a crystalline phase in these materials has been shown to shift theT g value towards higher temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02385650
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  • 7
    Electronic Resource
    Electronic Resource
    Vickers indentation anisometry on thin cylindrical materials (1982)
    Springer
    Journal of materials science 17 (1982), S. 3427-3430 
    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 required anisometric correction to be made when using Vickers indentations on filaments with radial dimensions of the order of those of the microindenter, is evaluated. For an isotropic plastic material the anisometry of indentation. Δl=l∥{-l 1 increases with decreasing cross-section of the filament. If the calculated correction, Δ/c, is in agreement with experiment the interest lies in the fact that the material preserves the indentation shape after removal of the indenter. Values of Δ/≠Δ/c reveal the presence of a mechanical anisotropy on metallic filaments due to processing. Furthermore, in the case of thin highly oriented polymeric fibres the inherent microindentation anisotropy is masked by the anisometry effect. Consequently, the proposed correction is very important and particularly valuable when anisotropic cylindrical material surfaces are being studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00752187
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  • 8
    Electronic Resource
    Electronic Resource
    Recent developments in the understanding of the microhardness of paraffins (1986)
    Springer
    Journal of materials science 5 (1986), S. 1183-1185 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF01742241
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  • 9
    Electronic Resource
    Electronic Resource
    Microhardness of sintered poly (4-hydroxybenzoate) and poly(2-hydroxy-6-naphtoate) homopolymers: Influence of pressure and morphology (1995)
    Springer
    Journal of materials science 14 (1995), S. 1571-1573 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00455418
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  • 10
    Electronic Resource
    Electronic Resource
    Time resolved USAXS study of the shish–kebab structure in PE: Annealing and melt crystallization (2000)
    Springer
    Journal of materials science 35 (2000), S. 5199-5205 
    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 Real time changes in the shish–kebab structure of high molecular weight polyethylene samples, produced by elongational flow injection moulding, were investigated by ultra small angle X–ray scattering (USAXS) using synchrotron radiation. The variation of the two typical long periods has been followed in situ, during heating and cooling from the molten state, as a function of temperature and time. Values of the length of the coherently diffracting domains perpendicular to the lamellar stacking planes, as derived from the USAXS maxima, are also presented. Results are discussed in the light of a shish–kebab model in which two different lamellar populations are respectively associated with an epitaxial growth from the columnar shish fibrils and with a secondary lamellar crystallization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004864606257
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