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  • 1
    Electronic Resource
    Electronic Resource
    Polystyrene degradation induced by stresses resulting from the freezing of its solutions (1976)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 14 (1976), S. 553-564 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solutions of polystyrene in p-xylene were frozen in liquid nitrogen. No changes in molecular weight and distribution were caused by freezing solutions for a series of narrow distribution polystyrenes with molecular weights of near 2 × 106 and lower. Likewise a commercial polystyrene of M̄w = 234,000 showed no change, even after 45 cycles of freezing and thawing. However, an ultrahigh molecular weight polystyrene (M̄w = 7.3 × 106) showed appreciable degradation even after a few freezing cycles of its solutions. The changes in molecular weight and distribution were analyzed by gel-permeation chromatography. The results depended very much on the choice of solvent, cooling rate, and concentration. The extent of degradation was found to depend on polymer concentration in two distinct ways. Indeed, two different degradation mechanisms have been distinguished at low and at high concentrations. The change between mechanisms took place between 1.0 and 2.5 g/l. for polystyrene in p-xylene. This appears to provide a rare measure of polymer-polymer interactions (entanglements) in dilute solutions. Degradation in the entanglement region proceeded via a random chain-scission mechanism as tested by the Scott method. In contrast, at low concentrations degradation was characterized by the formation of appreciable amounts of low molecular weight polystyrene. The presence of an antioxidant (Ionol) during freezing did not change the extent of degradation significantly.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1976.170140304
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  • 2
    Electronic Resource
    Electronic Resource
    Tensile properties of ultradrawn polyethylene (1975)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 13 (1975), S. 1177-1186 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: High-density polyethylene filaments prepared by a solid-state deformation in an Instron capillary rheometer show unusually high crystal orientation, chain extension, axial modulus, and ultimate tensile strength. The Young's modulus and ultimate tensile strength have been determined from stress-strain curves. Gripping of this high modulus polyethylene has been a problem heretofore, but the measurement of ultimate tensile strength has now been made feasible by a special gripping procedure. Tensile moduli show an increase with sample preparation temperature and pressure. Values as high as 6.7 × 1011 dyne/cm2 are obtained from samples extruded at 134°C and 2400 atm and tested at a strain rate of 3.3 × 10-4 sec-1. The effect of strain rate and frequency on modulus has also been evaluated by a combination of stress-strain data and dynamic tension plus sonic measurements over nine decades of time.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1975.180130610
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  • 3
    Electronic Resource
    Electronic Resource
    The morphology of ultradrawn polyethylene. I. Nitric acid etching plus gel permeation chromatography (1975)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 13 (1975), S. 2031-2048 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Transparent strands of high-density polyethylene of unusually high c-axis orientation have been produced by a solid-state extrusion, involving pressure, temperature, and deformation, in an Instron capillary rheometer. Measured values for tensile modulus are higher than previously reported for any polyolefin. Previous modulus and electron microscopic data are consistent with a strand morphology comprised (≤20%) of of extended chain crystals. The remainder resembles an oriented fibrillar morphology such as found in highly drawn polyethylene. In the present study, fuming nitric acid etching of the ultraoriented strands, in combination with gel permeation chromatography (GPC), has provided incisive structural information. The strands exhibit ≥3X the resistance to acid degradation shown by conventionally drawn polyethylene. GPC molecular weight distributions (MWD) of etched samples show a single broad peak with a prominent high molecular weight tail. The crystal size, represented by the MWD, is in agreement with the crystal long period determined by small-angle x-ray scattering. The absence of multiple peaks in the etched MWD's is evidence of limited chain folding. The extended chain content, determined from the etched MWD's, is a strong function of strand formation temperature and is in agreement with the fraction of extended chains calculated from modulus measurements.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1975.180131013
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  • 4
    Electronic Resource
    Electronic Resource
    Influence of extrusion ratio on the tensile properties of ultradrawn polyethylene (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 1729-1737 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The tensile properties have been evaluated for high-density solid-state polyethylene extruded to different extrusion (draw) ratios. The results are compared with measured and theoretical values on this and other polymers. An extrusion (draw) ratio and a deformation gradient are defined and discussed. The content of extended tie molecules in extruded high-density polyethylene was calculated from a model and modulus data.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180161003
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  • 5
    Electronic Resource
    Electronic Resource
    Physical and mechanical properties of ultra-oriented high-density polyethylene fibersPresented in part November, 1976, at the American Chemical Society, Division of Cellulose, Meeting on Paper and Textile Chemistry, University of Tennessee, Knoxville, TN. (1979)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 17 (1979), S. 859-892 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ultra-oriented high-density polyethylene fibers (HDPE) have been prepared by solid-state extrusion over 60-140°C range using capillary draw ratios up to 52 and extrusion pressures of 0.12 to 0.49 GPa. The properties of the fibers have been assessed by birefringence, thermal expansivity, differential scanning calorimetry, x-ray analysis, and mechanical testing. A maximum birefringence of 0.0637 ± 0.0015 was obtained, greater than the calculated value of 0.059 for the intrinsic birefringence of the orthorhombic crystal phase. The maximum modulus obtained was 70 GPa. The melting point, density, crystallinity, and negative thermal expansion coefficient parallel to the fiber axis all increase rapidly with draw ratio and at draw ratios of 20-30 attain limiting values comparable with those of a polyethylene single crystal. The properties of the fibers have been analyzed using the simple rule of mixtures, assuming a two-phase model of crystalline and noncrystalline microstructure. The orientation of the noncrystalline phase with draw ratio was determined by birefringence and x-ray measurements. Solid-state extrusion of HDPE near the ambient melting point produced a c-axis orientation of 0.996 and a noncrystalline orientation function of 0.36. Extrusion 50°C below the ambient melting point produced a decrease in crystallinity, c-axis orientation, melting point, and birefringence, but the noncrystalline orientation increased at low draw ratios and was responsible for the increased thermal shrinkage of the fibers.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1979.180170511
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  • 6
    Electronic Resource
    Electronic Resource
    Solid-state coextrusion of high-density polyethylene. I. Effects of geometric factors (1979)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 17 (1979), S. 2171-2180 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The solid (crystalline) state coextrusion of two high-density polyethylenes (HDPE) having weight-average molecular weights (Mw) of 59,000 and 200,000 have been studied as a function of the geometrical arrangement and the volume fraction of the components. The extrusion rate increased nonlinearly with the volume fraction of the low-Mw, component. The rate was faster when the low-Mw, component was the core rather than the sheath in the initial cylindrical concentric billet. Thus the slow extrusion rate of high-Mw HDPE alone was increased up to ten times by coextrusion with a small fraction of the low-Mw, HDPE component in its center. Generally, the deformation flow profile changed gradually from a parabolic to a W-shaped pattern as the volume fraction of the high-Mw, component increased. However, the geometric arrangement of the two different Mw components also had a pronounced effect on the deformation. The deformation patterns showed that upon coextrusion the low- and high-Mw HDPE's were extruded at the same rate and extrusion draw ratio. The geometrical arrangement had no substantial effects on the tensile modulus and strength of the extrudates; i.e., they increased linearly with volume fraction of the high-Mw HDPE.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1979.180171212
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  • 7
    Electronic Resource
    Electronic Resource
    Morphology of ultradrawn polyethylene strands. II. Nitric acid etching and melting behavior (1975)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 13 (1975), S. 2049-2065 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A transparent, ultraoriented, high-density polyethylene morphology has been produced by solid-state (ultradraw) extrusion in a capillary rheometer. From the perspective of modulus and nitric acid etching behavior, the uniquely high draw ratios (〈325) experienced by the polyethylene during extrusion result in a morphology with a high level of chain extension. The effect of nitric acid etching on strand thermal behavior has been determined by DSC. The observed melting points of unetched strands were sensitive to the thermal contact between sample and sample pan. Under conditions ensuring improved contact, strand superheating is reduced to one-third of previously reported values. The negligible shrinkage evidenced by these strands up to 130° is consistent with the presence of a thermally stable component such as extended chain crystals or crystallized tie chains. The single, high-melting peak is gradually replaced by a nonsuperheating, lower melting peak during the initial stages of acid etch. The resultant peak melting temperature is consistent with the value predicted for the peak crystal thickness of the etched polymer. No evidence is found for a higher melting peak attributable to the extended chain crystalline component. A highly constrained morphology produced by the large tie chain content is believed responsible for strand melting behavior. The melting point of the extended chain crystalline component is reduced by defects and a large ratio of lateral to basal surface area.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1975.180131014
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  • 8
    Electronic Resource
    Electronic Resource
    Dimensional changes in ultradrawn polyethylene (1977)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 15 (1977), S. 1427-1434 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Samples of ultradrawn high density polyethylene were studied by thermomechanical analysis. The purpose was to study the dimensional changes in polyethylene morphologies of extreme orientation. Dimensional changes were measured from -140 to +70°C with a precision of better than 1%. A negative thermal expansion coefficient was observed along the length (c axis) of the fibers containing the polyethylene morphologies of extreme orientation. A change in negative coefficient is observed between -35 and -45°C. The sign and magnitude of the expansion coefficient confirm, along with other evidence, the existence of extended chain structures in these morphologies. A series-parallel model has been developed for the ultradrawn polyethylenes to describe the dimensional changes with temperature.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1977.180150809
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  • 9
    Electronic Resource
    Electronic Resource
    Influence of extrusion ratio on the thermal properties and morphology of ultradrawn high-density polyethylene (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 1721-1728 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Solid-state extrusion of high-density polyethylene (HDPE) has received considerable attention. It has been shown that extrudate may have high values of optical clarity, tensile modulus (∼70 GPa = 7 × 1011 dyn/cm2), and c-axis orientation. The effects of extrusion conditions on the properties of the resultant fibers have, however, not yet been clarified. A systematic study has thus been made here to evaluate extrusion pressure, temperature, and extrusion (draw) ratio, and the molecular weight of extruded HDPE. The effects of extrusion ratio on the degree of crystallinity, melting behavior, crystal orientation, and dimensional change along the extrusion direction are reported.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180161002
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  • 10
    Electronic Resource
    Electronic Resource
    Steady-state and dynamic rheology of poly(1-olefin) melts (1978)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 16 (1978), S. 1709-1719 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The steady-state and dynamic melt rheology for a series of poly(1-olefins) has been investigated. The series includes poly(1-butene), poly(1-hexene), poly(1-heptene), poly(1-octene), Poly(1-undecene), poly(1-tridecene), poly(1-hexadecene), and poly(1-octadecene). The flow behavior was investigated by use of a Weissenberg rheogoniometer. Measurements on poly(1-butene) were also made using an Instron capillary rheometer. The empirical relationship developed by Cox and Merz was obeyed for the entire series of poly(1-olefins) at all temperatures investigated. Graessley's theory was used to calculate the flow curves for the poly(1-olefins) from the measured molecular weight distributions. The purpose was to investigate the effect of polymer composition on the shear rate dependence of viscosity. It was found that all experimental flow curves except those for poly(1-hexene) can be fitted with the calculated curves from the individual molecular weight distributions. The conclusion is made that flow curves of poly(1-olefins) depend predominately on molecular weight distribution and are essentially independent of side-chain length even for poly(1-olefins) with pendant groups as long as 16 carbon atoms. The low-shear limiting Newtonian viscosity η0 for all poly(1-olefins) was expressed by, η0 = KM̄w3.4 or by η0 = K′P̄w3.4 where M̄w is the weight-average molecular weight and P̄w is the weight-average degree of polymerization. The K and K′ values obtained decrease systematically as the side chain is increased.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1978.180161001
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