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  • 1
    Electronic Resource
    Electronic Resource
    Morphological changes in pressure annealed polyethylene (1996)
    Springer
    Journal of materials science 31 (1996), S. 5541-5549 
    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 Polyethylene samples have been annealed under high pressures in order to transform the morphology and thereby make specimens, which on subsequent orientation by hydrostatic extrusion, produce high-modulus materials for comparatively low deformation ratios. The pre-extrusion morphology, as revealed by permanganic etching followed by transmission electron microscopy, is shown to be highly sensitive to the annealing conditions, especially in the vicinity of the orthorhombic/hexagonal phase boundary. The morphological changes have also been studied by gel permeation chromatography of nitrated samples and by differential scanning calorimetry. The moduli of samples, extruded to a standard extrusion ratio of 7, reflect differences in the morphology of the starting material. It is shown that the highest modulus is not obtained by annealing totally within the hexagonal phase but rather in the changeover region between it and the orthorhombic phase. Although the lamellar size can be dramatically increased by annealing within the hexagonal phase, this development occurs at the expense of reducing the integrity of the molecular network so that for high lamellar size the modulus falls and the samples become increasingly incoherent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01159328
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Structural changes in solvent-induced crystallization of quenched isotactic polypropylene (1989)
    Springer
    Colloid & polymer science 267 (1989), S. 661-667 
    Details
    ISSN: 1435-1536
    Keywords: Polypropyleneisotactic ; crystallization insolvents ; wide anglex-rayscattering ; density ; differentialscanningcalorimetry ; morphology ; transmissionelectronmicrograph
    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 Solvent-induced crystallization of quenched isotactic polypropylene (iPP) films in dichloromethane, cyclohexane, carbon tetrachloride, and chloroform has been investigated. WAXD, density, and DSC measurements indicate that smectic iPP films undergo a complex rearrangement of the structure in these liquids, leading to a process of crystallization. Transport properties of the dried samples, after the solvent treatment, show that the first stage of crystallization involves, in addition to the smectic phase, a fraction of amorphous phase, while further crystallization regards only the smectic phase. The morphology of the crystallized samples has been investigated by transmission electron microscopy following permanganic etching. No change in the basic morphology is found, although local organization showing splaying and branching appears clearer in the solvent crystallized samples than in the starting smectic sample.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01524368
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  • 3
    Electronic Resource
    Electronic Resource
    The hot compaction of SPECTRA gel-spun polyethylene fibre (1997)
    Springer
    Journal of materials science 32 (1997), S. 4821-4832 
    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 compaction of gel-spun high molecular weight polyethylene (PE) fibre, SPECTRA 1000, has been investigated for a range of compaction temperatures between 142°–155°C. Differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and broad-line nuclear magnetic resonance (NMR) techniques have been used to examine the structure of the compacted materials and to determine the compaction mechanisms. With increasing compaction temperature, the flexural properties of the compacted materials did not show any significant change up to 154°C, but large changes were observed if the temperature was increased from 154 to 155°C. DSC and SEM studies revealed that no evident surface melting and recrystallization occurred during hot compaction in the temperature range 144–154°C, although the rigid crystalline fraction measured by NMR for all compacted materials is significantly lower than that for the original fibre. Significant transverse strength is also developed at the lower compaction temperatures, and this also only markedly increases on going from 154 to 155°C. Structural investigations show how the fibres deform so as to interlock, and localized welding occurs, so as to bond each fibre to its neighbour. This is distinct from the melting and recrystallization at the surface of the fibres previously observed in melt spun fibres.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018647401619
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  • 4
    Electronic Resource
    Electronic Resource
    The hot compaction of polypropylene fibres (1996)
    Springer
    Journal of materials science 31 (1996), S. 1157-1163 
    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 Investigation of the compaction of unidirectionally arranged high-tenacity polypropylene fibres is described. A combination of techniques, with the major emphasis being morphological studies, show that controllable “selective” surface melting is not achieved at a high enough proportion to give substantial fibre-to-fibre bonding, and hence good lateral strengths.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00353094
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  • 5
    Electronic Resource
    Electronic Resource
    The hot compaction of polyethylene terephthalate (1995)
    Springer
    Journal of materials science 30 (1995), S. 615-622 
    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 process is described for the successful compaction of polyethylene terephthalate fibres. The measurement of mechanical properties shows that a very high proportion of the original fibre properties are retained and that the compacted samples have a good degree of coherence. Electron microscopy studies of suitably etched samples reveals the effect of the compaction temperature on the structure of the compacted samples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00356319
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  • 6
    Electronic Resource
    Electronic Resource
    Differential melting in compacted high-modulus melt-spun polyethylene fibres (1995)
    Springer
    Journal of materials science 30 (1995), S. 601-606 
    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 compaction of high-modulus melt-spun polyethylene fibres has been investigated for compaction temperatures above the optimum. After such treatment the specimens are liable to be non-uniform because of differential melting. Individual compacted fibres are observed to melt not only from the outside inwards, but also in certain internal regions, depending upon the availability of local free volume. The regions of different stability have been identified and inferences drawn concerning the structure of the initial fibres. It is suggested in particular that the longitudinal regions of deficit density (which exhibit cratering in transverse sections and melt before their surroundings) are a result of initial crystallization occurring within a rigid framework inside the fibre, possibly nucleated on a strained molecular network. The presence of banded recrystallization around residual fibres demonstrates that this phenomenon develops via interaction of neighbouring lamellae as they grow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00356317
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  • 7
    Electronic Resource
    Electronic Resource
    Delineating water trees in cross-linked polyethylene: a new technique (1992)
    Springer
    Journal of materials science 27 (1992), S. 5192-5198 
    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 new technique has been developed to image water trees in polymeric insulated cables. The method is based upon permanganic etching and enables water trees to be examined either optically or by electron microscopy. Use of transmission electron microscopy allows the water tree and matrix microstructures to be imaged simultaneously. Relationships between polymer morphology and water-tree growth may therefore be studied. The technique and its application to the study of water-tree microstructure in cross-linked polyethylene using optical, scanning electron and transmission electron microscopy, is described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02403815
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Delineating water trees in cross-linked polyethylene: a new technique (1992)
    Springer
    Journal of materials science 27 (1992), S. 5192-5198 
    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 new technique has been developed to image water trees in polymeric insulated cables. The method is based upon permanganic etching and enables water trees to be examined either optically or by electron microscopy. Use of transmission electron microscopy allows the water tree and matrix microstructures to be imaged simultaneously. Relationships between polymer morphology and water-tree growth may therefore be studied. The technique and its application to the study of water-tree microstructure in cross-linked polyethylene using optical, scanning electron and transmission electron microscopy, is described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00553390
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    Compaction of high-modulus melt-spun polyethylene fibres at temperatures above and below the optimum (1994)
    Springer
    Journal of materials science 29 (1994), S. 4694-4699 
    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 the process of hot compaction developed at the University of Leeds, high-modulus fibres are compacted to form coherent thick-section products with stiffnesses unobtainable by current processing techniques. Using high-modulus polyethylene fibres (trade name TENFOR) produced by the melt-spinning/hot-drawing route as the starting material, it was discovered that under optimum conditions of pressure and temperature it is possible controllably to melt a small proportion of each fibre. On cooling, this molten material recrystallizes to bind the structure together and fill all the interstitial voids in the sample, leading to a substantial retention of the original fibre properties. For a hexagonal close-packed array of cylinders, only 10% of melted material is needed for this purpose. If the compaction temperature is too low, there is insufficient melt to fill the interstices, the fibres deform into polygonal shapes, and insufficient transverse strength is developed. Above the optimum temperature, the proportion of melt increases, causing the stiffness of the composite to be reduced. The recrystallization of the melt is nucleated on the oriented fibres, giving similarly oriented cylindrulitic growth. Where the regions of melt are large enough, and cooling sufficiently rapid, development away from the nucleus is accompanied by a cooperative rotation in chain orientation, analogous to banding in spherulites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00356511
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  • 10
    Electronic Resource
    Electronic Resource
    The hot compaction of high modulus melt-spun polyethylene fibres (1993)
    Springer
    Journal of materials science 28 (1993), S. 316-324 
    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 production of solid section highly oriented polyethylene by compaction of melt-spun polyethylene fibres is described. Differential scanning calorimetry, X-ray diffraction and electron microscopy have been used to determine the structure of the compacted polymer. The essential feature of the process is shown to be selective surface melting of the fibres to form a polyethylene/polyethylene composite of very high integrity, yet maintaining a very high proportion of the strength and stiffness of the fibres.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00357801
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