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  • Polymer and Materials Science  (16)
  • Cervical spine  (2)
  • HPLC  (2)
  • Class II A
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  • 1
    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: The composition of sol- and gel-phases as formed during precipitation fractionation in various systems polymer-solvent-nonsolvent is examined analytically.It is shown that the polymer concentration in the gel-phase is independent of the initial concentration of polymer in the solution. The polymer concentration of the gel-phase increases with increasing molecular weight, if the nonsolvent-solvent-ratio is kept constant.The nonsolvent-solvent-ratio in the gel-phase is always smaller than in the corresponding sol-phase, it is constant during the early steps of fractionation and decreases slightly at the end of fractionation.
    Notes: Die Zusammensetzung der Sol- und Gelphasen, wie sie bei der Fällfraktionierung in verschiedenen Systemen Polymer-Lösungsmittel-Fällungsmittel gebildet werden, wird analytisch untersucht.Dabei zeigt sich, daß die Konzentration des Polymeren in der Gelphase unabhängig von der Ausgangskonzentration des Polymeren ist. Bei konstantem Fällungsmittelgehalt der Solphase nimmt die Polymerkonzentration in der Gelphase mit steigendem Molekulargewicht zu.Das Fällungsmittel-Lösungsmittel-Verhältnis in der Gelphase ist stets geringer als in der korrespondierenden Solphase. Es ist im Laufe einer Fraktionierung zunächst konstant und nimmt gegen Ende der Fraktionierung langsam ab.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: By partial sulfonation, desulfonation and ion exchange polytsyrene sulfonic acid resins were synthesized having the same capacity (1.3 milliequivalents/g). By the variation of the preparation methods, however, the distribution of the acid groups within the resins could be changed in a defined way so that different concentration profiles were obtained. It is shown that the properties and reaction behavior of the polymeric resins are determined to a large extent by the local concentration of the functional groups.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 14 (1970), S. 1927-1938 
    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: All current fractionation techniques - based on sol-gel equilibria - are characterized by a variation of the solvent power after each fractionation step in a discontinuous as well as in a continuous way. Overlapping of consecutive fractions is the consequence of this procedure. It can be shown that this overlapping can be diminished essentially by a multistage technique based on complete extraction at a given solvent power which then will be changed in discontinuous steps. As a further consequence, it is possible to obtain very homogeneous fractions of M̄w/M̄n 〈 1.03. A theoretical analysis of this technique on the basis of phase equilibrium data will be given, the results of which can be confirmed experimentally.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It is proposed that the mobility of sufficiently long molecules undergoing translational diffusion through solid polyethylene is significantly reduced by tie molecules and fixed entanglements within the interlamellar regions of the matrix. The effect on the diffusion coefficient both of diffusant molecular length and of the host matrix morphology is considered, and a semiquantitative relation between them obtained. This indicates that the mobility of long diffusants is higher in polyethylene which has been cooled slowly from the melt than it is in quenched polyethylene, in marked contrast to the behavior of gaseous and other small diffusants.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The diffusion coefficient for two diffusants of the type n-(CH2)NX is measured, where N ≃ 25, 45 and X is a suitable label; the matrix is linear polyethylene cooled at two widely differing rates from the melt. The measuring technique used is a recently developed one based on infrared microdensitometry. The results indicate that these diffusants diffuse faster in the slowly cooled matrix, in marked contrast to the behavior of gaseous diffusants. They are in agreement with the predictions of the model developed in a previous paper (part I), in which the constraints imposed by interlamellar tie molecules on long diffusants were shown to be important.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Direct depth profiling techniques to date have largely lacked the necessary depth resolution to investigate interfacial phenomena of the order of the bulk correlation length (5 - 10 nm for a wide range of systems). Here we investigate the optimal spatial resolution and depth of probe that may be attained for composition  -  depth profiling of polymeric samples via nuclear reaction analysis (NRA) using the 2H(3He, 1H)4He reaction. We find that the spatial resolution can be greatly improved by using a grazing incidence geometry of the incident 3He beam on the sample, and analyzing the emitted protons in a backwards direction. This results in spatial resolutions down to about 3 nm at the sample surface, compared to a value of some 7 nm or more previously reported in earlier studies when emitted α-particles were detected in the forward direction. At the same time the depth to which samples can be profiled via the backwards emitted protons may be considerably extended relative to the α-particle detection mode, when the 3He beam impinges on the sample surface at normal incidence (up to about 4 μm into the sample for incident energies of 1.2 MeV in the proton-detection mode compared to only 1 μm for the equivalent α-particle detection mode).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-1211
    Keywords: Key words Mhc ; Class II A ; Cichlid ; Fish ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0887-6266
    Keywords: tensile drawing ; morphology ; polybutylene ; terephthalate ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The concept of the drawing of a molecular network has been employed to derive a total network draw ratio from the combination of the two deformations occurring in the production of poly(butylene terephthalate), PBT, fibers by the consecutive processes of melt spinning and cold drawing. The mechanical properties of PBT can then be more readily explained in terms of increases in this total network draw ratio. However, the preorientation and crystallization that occurs in the melt-spinning process can occur at different strain rates and temperatures, depending on the wind up speed employed, on the extensional viscosity of the polymer, and on the variation of the extensional viscosity with temperature. Therefore, for polymers such as poly(butylene terephthalate), which can exist in two crystalline forms, the morphology of the final drawn fiber might be expected to depend on the first melt-spinning stage of the process as well as on the total network draw ratio. In this work, density, birefringence, mechanical measurements, and WAXD measurements, which have been made on the melt-spun fibers and on the drawn fibers, are described. Small differences in some of the drawn yarn mechanical properties at the same overall network draw ratio are related to the crystallinity and in particular to differences in the proportion of the α and β phases present in the drawn yarn. These in turn are related to differences in the temperature and stress during melt spinning and drawing. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2465-2481, 1997
    Additional Material: 18 Ill.
    Type of Medium: Electronic Resource
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