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  • 1
    Electronic Resource
    Electronic Resource
    Structural morphology and compaction of nascent high-density polyethylene produced by supported catalysts (1991)
    Springer
    Journal of materials science 26 (1991), S. 3171-3179 
    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 morphologies of three nascent high-density polyethylene (HDPE) powders, polymerized in the gas phase by different catalysts, were investigated using scanning electron microscopy (SEM). Silica-supported catalyst systems comprising TiCl4/MgCl2,bis(triphenylsilyl)chromate andbis(cyclopentadienyl)chromium were found to produce polymers with globular, nodular and worm-like microstructures, respectively. The topographies of the fluff particles are related to the compaction behaviour of the HDPE powders. Long, worm-like strands that protrude from the particles are capable of forming more extensive entanglements than the shorter, nodular structures. The entanglements are the main cause of agglomeration of the particles during their long-term bulk storage. Furthermore, the rate of thermal oxidation is influenced markedly by the polymer microstructure. The microstructure determines the surface area available for oxygen attack. High-resolution SEM combined with low-temperature plasma etching reveals that the worm-like structures consist of folded-chain lamellae that are coiled around a core of extended chains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01124659
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  • 2
    Electronic Resource
    Electronic Resource
    Double torsion fracture testing of high-density polyethylene (1994)
    Springer
    Journal of materials science 29 (1994), S. 6026-6032 
    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 fracture of polyethylene has been studied extensively using conventional testing geometries such as three-point bending (TPB) and single-edge notch tension (SENT). These geometries are of limited utility for studying crack growth, because the crack speed is constantly changing and the crack front is in the centre of the specimen. Double torsion (DT) is a fracture geometry that suffers neither of these disadvantages, yet has only received limited attention in the literature. Its use has been limited to highly brittle materials such as glass, ceramics, thermosetting plastics and PMMA. In contrast to these materials, high-density polyethylene (HDPE) is an inherently ductile polymer. Before the advantages of DT can be exploited for testing HDPE, it is first necessary to demonstrate the validity of DT fracture measurements performed on such a ductile material. In this paper it is shown that at moderate rates of loading and at temperatures below 0
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00366889
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  • 3
    Electronic Resource
    Electronic Resource
    The morphology, chain structure and fracture behaviour of high-density polyethylene (1995)
    Springer
    Journal of materials science 30 (1995), S. 3351-3357 
    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 High-density polyethylene (HDPE) is being used more and more in critical long-term applications. For this reason it is important to have a strong understanding of those parameters which control the fracture behaviour of HDPE. In Part I of this work, fracture results were presented for eleven HDPE samples tested using a tensile testing machine. Such short-term tests do not accurately reflect the in-service loads on HDPE components, which tend to be low and static. It is, therefore, important to perform fracture tests under long-term static loads. The results of such testing are presented in this paper. The resistance to static fatigue was found to be most strongly dependent on molecular weight. Short branch concentration and short branch length were also found to exert an influence on the resistance to static fatigue. This result is similar to the findings presented in Part I of this work. However, there is some evidence that molecular weight influences fracture behaviour to a greater extent in the long-term tests. Notwithstanding, the similarity between the short-term and long-term results is important. It means that an early indication of the long-term performance of HDPE resins can be obtained from rapid comparative tests conducted using a tensile testing machine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349879
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  • 4
    Electronic Resource
    Electronic Resource
    The morphology, chain structure and fracture behaviour of high-density polyethylene (1995)
    Springer
    Journal of materials science 30 (1995), S. 3307-3318 
    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 fracture behaviour of high-density polyethylene has only recently become the subject of comprehensive studies. Few of these studies have utilized a group of resins with systematic variation in molecular properties. In this work, a series of samples with controlled variation in chain structure have been prepared using commercial polymerization facilities. The fracture behaviour of these samples has been measured at both a constant rate of deflection and in static fatigue. Comprehensive statistical techniques were used to correlate these fracture results with the chain structure and morphology of the samples. Part I of this work presents the results for the work conducted at a constant rate of deflection. Both the fracture toughness and crack-growth rate were found to be most strongly dependent on the molecular weight of the resin. This is not an unexpected result. However, when variations in molecular weight are minimal, it was found that increasing the short branch content offers considerable scope for improving the fracture performance. Furthermore, longer short branches were found to be more effective at enhancing fracture behaviour. These results, which are of significant commercial importance, are interpreted in terms of existing models for the fracture process in polyethylene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349874
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  • 5
    Electronic Resource
    Electronic Resource
    Evaluation of the crack shape and activation energy for fracture in double torsion fracture tests of high density polyethylene (1995)
    Springer
    Journal of materials science 14 (1995), S. 340-343 
    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/BF00592144
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  • 6
    Electronic Resource
    Electronic Resource
    The strain rate dependency of fracture in polyethylene: Fracture initiation (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 38 (1989), S. 339-350 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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: The dependency of fracture on the rate of strain of a range of polyethylene samples was measured in three point flexural tests at 23°C. The range of strain rates from 10-1 to 10-7 reciprocal seconds was examined. The J integrals at the initiation of the cracks were determined. This enabled the interrelationship between fracture initiation and the test rate to be established. The dependency follows a power law relation. The values of the exponents in the power law equations, derived from experiment, were found to be higher than the values calculated using established criteria for crack initiation. The difference is postulated to be due to the strengthening of the fibrils ahead of the crack because of the orientation of the fibrils in that region.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1989.070380215
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  • 7
    Electronic Resource
    Electronic Resource
    Dynamic mechanical properties of glass-filled epoxy resin (1974)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 12 (1974), S. 1555-1564 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Composite specimens were prepared using soda glass beads and a purified epoxy resin cured with 1,3-propylene diamine. Some beads were treated with a silane coupling agent. The dynamic mechanical properties of these specimens were measured in the temperature range -190 to +180°C using a free-oscillation torsion pendulum. The dynamic mechanical relaxation spectrum showed no feature that could be attributed to the formation of a new interfacial phase and the torsional moduli were unaffected by the use of the coupling agent. Increasing the glass content of the specimens decreased the damping and increased the modulus. An attempt was made to predict the composite modulus using the Kerner equation. When the specimens were immersed in boiling water, two effects were noted. First, water was absorbed in the epoxy resin matrix and changes in the dynamic spectrum were observed. Second, in samples filled with untreated glass debonding occurred and the presence of free water at the interface was indicated by the appearance of a new peak near 0°C.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1974.180120804
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  • 8
    Electronic Resource
    Electronic Resource
    Relaxations in the transition region of crosslinked polyesters. II. The glass transition (1974)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 12 (1974), S. 1925-1937 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The glass-transition region of crosslinked polymers prepared from poly(1,2-propylene phthalate fumarate) and styrene was studied using a torsion pendulum. The glass-transition temperature and the modulus in the rubbery region of these polymers were analyzed in terms of the crosslink density. The styrene concentration at which the maximum crosslink density occurs, as estimated from the viscoelastic data, is found to be in agreement with estimates made by other workers using chemical methods.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1974.180120914
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  • 9
    Electronic Resource
    Electronic Resource
    Relaxations in the transition region of crosslinked polyesters. I. The β relaxation (1974)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 12 (1974), S. 2111-2118 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The glass transition region of styrene-crosslinked poly(1,2-propylene phthalate fumarate) was studied using a torsion pendulum. The region was composed of two separate relaxations. The major relaxation was the glass transition of the whole network, while the minor relaxation, at a lower temperature, was ascribed to the polyester segments between the crosslinks. A comparison was made between these relaxations and these observed in related polyester networks.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1974.180121011
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  • 10
    Electronic Resource
    Electronic Resource
    Low-temperature relaxations in styrene-crosslinked polyester networks (1975)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 13 (1975), S. 1049-1056 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Two low-temperature dynamic mechanical relaxations have been observed in networks formed by copolymerization of poly(1,2-propylene fumarate) and poly(1,2-propylene phthalate fumarate) with styrene. The γ relaxation which occurs around -100°C (1 Hz) is induced by small amounts of water, while the broad γ′ relaxation is reduced in height by the presence of water. Neither xylene nor 1,2-propylene glycol induced a γ relaxation. The γ relaxation was ascribed to motions involving a fumarate ester group-water complex.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1975.180130516
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