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  • 1
    Electronic Resource
    Electronic Resource
    Radical formation during the tensile failure of polymer fibers (1973)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 171 (1973), S. 211-227 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Bruch von linearen Makromolekülen als Folge der Dehnungsdeformation von orientiertem Nylon 6 wurde mit Elektronenspinresonanz (ESR) an zwei Proben, einer Einzelfaser (Borste) und technischem, weing verdrilltem Garn, untersucht. Die Ergebnisse an der Einzelfaser zeigen, daß die Dehnungsdeformation in einer wesentlichen, irreversiblen Weise die Konzentration der freien Radikale, doch nicht die Bruchspannung und Deformation beeinflußt. Das mechanische Verhalten des Garns in Bruchnähe ist völlig verschieden von dem der Einzelfaser. Die vorliegenden Versuche lassen ernste Zweifel aufkommen an der Korrektheit frühererBerichte, in denen angenommen wurde, daß die mittels ESR beobachteten Kettenbrüche eindeutig den Deformations- und Bruchprozeß bestimmen.
    Notes: Bond rupture associated with the tensile deformation of oriented Nylon 6 has been studied by electron spin resonance (ESR). Two samples were investigated, a single monofilament (“bristle”) and a commercial low twist yarn. Experiments with the monofilament show that tensile deformation has substantial irreversible effects on the free radical concentration observed at failure, but no effect on the ultimate properties of the fiber. It was also demonstrated that the stress-strain behavior of the yarn is quite different from that of the fibers near the ultimate extension. These present experiments raise serious questions as to the correctness of previous reports in which the bond breakage observed by ESR is assumed to uniquely determine the deformation and fracture process.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1973.021710120
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  • 2
    Electronic Resource
    Electronic Resource
    Decay of the spin echo in a pulsed magnetic field gradient NMRDedicated to Prof. O. Wichterle on the occassion of his 70th birthday (1983)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 184 (1983), S. 2377-2390 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The additional attenuation of the spin echo of a pulsed magnetic field gradient NMR caused by the diffusion of the spins carrying molecules is calculated for a time dependent diffusion coefficient. The cases of a Constant D0, of an exponential decay with time, and an abrupt drop from D0 to zero at time t0 are considered. In all cases the time dependence of the experimentally observed attenuation is less steep than that of D. The time scale, however, Changes very little. The calculation was based on the consideration that the diffusion transports the precessing spins to a location with a different Larmor frequency so that a complete reversal after the 180° pulse is not possible any more. Hence, any deviation from a straight line in a plot of the excess attenuation versus δ2(1 - δ/3Δ) may by interpreted in terms of a time dependence of the diffusion coefficient.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1983.021841117
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  • 3
    Electronic Resource
    Electronic Resource
    Monoplanar small angle neutron scattering by semicrystalline polymer solids containing homogeneously distributed otherwise identical deuterated polymer molecules (1989)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 190 (1989), S. 1623-1633 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The first “linear” range of inverse reduced scattering intensity of N stems in monodisperse clusters versus q2 with the initial slope Rcc2/2 is followed by a second nearly 20% steeper and 10 times wider quasi-linear range. The difference slightly decreases with polydispersity of the clusters. This case will not be discussed here. One may deduce from the second range the fictive number N of stems and gyration radius Rcc which differ less than 10% from the true values obtained from the first “linear” range. But the fine structure of the equal monoplanar clusters on the scattering molecule may change enormously with interior gaps while keeping constant the scattering intensity in the interesting region, N and Rcc of the cluster. In the sensitive range of the first two quasi-linear ranges all these 3 quantities are so little affected by the changes of fine structure that small angle neutron scattering (SANS) yielding N and Rcc does not permit any statement on these changes. The calculations of SANS results with some equidistant gaps which retain N and Rcc yield the same intensity distribution in the interesting range. This follows from the fact that N commands the intensity while Rcc rules not only the first but also the second quasi-linear range. The perfect merging of the first with the second quasi-linear ranges in the SANS of polyethylene demands a special arrangement of a single gap separating one single stem from the bulk of the active stems in the cluster.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1989.021900714
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  • 4
    Electronic Resource
    Electronic Resource
    Bond rupture in highly oriented crystalline polymers (1969)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1151-1163 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The strength-limiting process in the fracture of semicrystalline fibers and highly oriented films is the rupture of tie molecules connecting the folded chain lamellae in the machine direction. This view is supported by the data on stress and temperature dependence of lifetime of fibers under load and on radical formation during the fracture experiment. The observed tensile strength, however, is about 10 times smaller and the number of fractured chains between 100 and 1000 times larger than expected on the basis of the known number of tie molecules in the fracture plane. This discrepancy is a consequence of the inhomogeneity of the micromorphology of fiber structure, which causes a much larger stress concentration on the most unfavorably located tie molecules than the average value one would expect in the case of perfectly uniform stress distribution on identical tie molecules. The fluctuation of amorphous layer thickness, of number and length of tie molecules, produces such a high stress concentration on some tie molecules throughout the sample that they rupture long before the average stress concentration is sufficient for chain fracture. By accumulation of damage caused by gradual chain rupture the weakening of the sample locally proceeds so far that at the maximum damage concentration, microcracks start to form, and the fiber breaks.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1969.160070702
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  • 5
    Electronic Resource
    Electronic Resource
    Spin lattice relaxation in linear polyethylene (1969)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1165-1186 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The proton spin-lattice relaxation times (T1) of linear polyethylenes (PE) of varying morphology were measured as a function of temperature. The T1 of oriented bulkcrystallized and solution-crystallized material was isotropic, in disagreement with calculations based on a sample dipole pair model. Motion in the non-crystalline regions of the samples is shown to be responsible for the T1 minimum occurring around -20°C. The dependence of T1 at the minimum on the long period reinforces the model of an amorphous fraction composed of disordered lamellar surface layers. The temperature of the T1 minimum and the dependence of T1 on the long period imply that the mobility of these amorphous regions is reduced in cold-drawn and solution-crystallized samples. This mobility irreversibly increases with annealing. In highly relaxed samples the motion of a small portion of the disordered regions is almost liquidlike, as indicated by the presence of a second shorter T1.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1969.160070703
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  • 6
    Electronic Resource
    Electronic Resource
    The limiting axial long period of drawn polypropylene (1969)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 7 (1969), S. 1275-1278 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1969.160070707
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  • 7
    Electronic Resource
    Electronic Resource
    NMR study of molecular motion in oriented long-chain alkanes. II. Oriented mats of polyethylene single crystalsPresented at the Meeting of the American Physical Society, Berkeley, Calif., March 1968. (1970)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 8 (1970), S. 771-789 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Measurements of the NMR second moment of a uniaxially oriented sample of polyethylene single crystals in the range of temperatures from -196°C to 130°C and its dependence on the alignment angle γ between the orientation axis (preferential direction of the molecular chains) and the NMR magnetic field are presented. The experimental results are discussed mainly with respect to the high temperature relaxation, called the α process, in polyethylene. They are compared to theoretical predictions made for a number of mechanisms of molecular motion in Part I of this work. Only one of the mechanisms considered is found to be in quantitative agreement with experiment, the mechanism here referred to as flip-flop motion. This consists of thermally activated rotational jumps of the crystalline chain segment between folds around its axis between two equilibrium sites in the lattice. Each rotational jump through 180° is accompanied by a shift of the molecule along its axis by one CH2 group. The discussion of the low-temperature relaxation of polyethylene, the γ process, is based partly on the above measurements and partly on measurements of second moments for unoriented polyethylene samples varying widely in morphology and noncrystalline content. The decrease of the second moment observed with these samples between -196°C and 20°C is taken as a measure of the intensity of the γ process. A linear correlation is found between the decrease in the second moment, designated ΔS, and the noncrystalline content, 1 - αm; this can be represented by ΔS = 1.4 + 22.1(1 - αm). It is shown that neither the crankshaft mechanism not the kink mechanism is able to account quantitatively for this result. The model of a chain end moving in a vacancy fails to adequately describe the angle dependence of ΔS in oriented polyethylene single crystals. The “sandwich model” of a polyethylene single crystal, in which the crystalline core is covered by noncrystalline surface layers, is in better agreement with observations.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1970.160080510
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  • 8
    Electronic Resource
    Electronic Resource
    Sorption of organic vapors into drawn and undrawn polyethylene (1967)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 5 (1967), S. 957-972 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Drawing of linear polyethylene at 60°C. to an extension ratio of ten drastically reduces the sorption and diffusion of n-pentane, benzene, methylene chloride, and tetrachloroethylene. Methylene chloride was chosen for more detailed study. The sorption is of the normal Fickean type. It is also fully reversible in the temperature range between 25 and 45°C. if the sorbed amount is kept to below 0.5%. At higher concentrations the sample relaxes so that sorption irreversibly increases. The reversible sorption per gram of amorphous component is about 1/6 of that in undrawn polyethylene. The diffusion constant has a larger temperature and concentration dependence than in the undrawn material. At zero concentration the activation energy for diffusion is 34.4 kcal./mole and the diffusion constant at 25°C. is 8 × 10-11 cm.2/sec. as compared with 14.4 kcal./mole and 1.5 × 10-8 cm.2/sec. in undrawn PE. Cold drawing reduces the sorption sites without changing their energy content, but drastically cuts down diffusion and increases the activation energy. A smaller part of the increase of the latter is a consequence of the lower enthalpy of the amorphous material and a larger part is probably due to the increased distance between sorption sites.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1967.160050512
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  • 9
    Electronic Resource
    Electronic Resource
    NMR observations of drawn polymers. V. Sorption into drawn and undrawn polyethylene (1966)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 4 (1966), S. 587-598 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: NMR measurements on undrawn polyethylene (PE) samples in contact with a solvent such as C2Cl4 indicate an increase in the mobility of the mobile chain segments as compared to dry samples. Highly drawn PE shows no such effect. This is because Sa, the sorption per unit mass of noncrystalline material present, decreases from 20.9 wt.-% (dry basis), found for undrawn quenched PE, to 0.63 wt.-% after drawing (Sa determined at 25°C. and 0.80 vapor activity). Drawing also reduces the segment mobility according to the NMR spectrum. It is shown that these effects are caused by considerable structural changes occurring in the noncrystalline regions of PE upon drawing. Annealing of drawn PE samples at successively higher temperatures leads to a gradual relaxation of the noncrystalline regions towards the state characteristic of undrawn PE. With increasing annealing temperature Sa as well as the mobility approach values found with undrawn PE.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1966.160040404
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  • 10
    Electronic Resource
    Electronic Resource
    Fuming nitric acid treatment of polyethylene. IV. Morphology of drawn polyethylene (1968)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 6 (1968), S. 587-605 
    Details
    ISSN: 0449-2978
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Drawn PE of different draw ratios (ranging from 1 to 25) and thermal treatment (annealing temperature 80, 100, 110, 120, 127°C.) was treated with fuming nitric acid at 80°C. Weight loss, molecular weight, elastic modulus, and thermograms were measured for annealed and unannealed samples as a function of the treatment time and draw ratio. As a consequence of the preferential oxidation of the noncrystalline portions, there occurs initially a high rate of weight loss and a steep drop in molecular weight, followed by a lower rate of weight loss at nearly constant molecular weight. The elastic modulus stays practically constant up to the moment where the brittleness of the sample prevents further measurement. During the later period the thermograms exhibit one melting peak during the first melting. The remelt of the same sample, however, has two melting peaks with a relative intensity independent of the treatment time. That the two melting peaks are caused by two components of different molecular weights present in the sample is substantiated by fractionation. At very high annealing temperature (127°C.), two peaks appear, not only in the first melting curve of the etched sample, but also in the melting curve of the unetched material. Such an effect is the consequence of partial melting during annealing followed by new crystallization during cooling the sample to room temperature. The findings are related to the morphology of the drawn material under the assumption of preferential scission of chain loops in the amorphous-crystalline sandwich layer model.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1968.160060313
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