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  • Chemistry  (10)
  • 1990-1994  (7)
  • 1970-1974  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Polymer-polymer miscibility evaluation by acoustic emission (1992)
    Basel : Wiley-Blackwell
    Die Makromolekulare Chemie, Rapid Communications 13 (1992), S. 45-53 
    Details
    ISSN: 0173-2803
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/marc.1992.030130108
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  • 2
    Electronic Resource
    Electronic Resource
    Theory-based improvements of continuous polymer fractionation demonstrated for poly(carbonate) (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 45 (1992), S. 1265-1279 
    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: For the first time, a quantitative theoretical analysis (liquid/liquid phase equilibria treated by means of the continuous thermodynamics) of the operating characteristics of continuous polymer fractionation (CPF) was performed. The results of these calculations were compared with data published for CPF of polyethylene. It turned out that the efficiency of the conventional CPF corresponds to approximately two theoretical plates only. For this reason, several improvements, suggested by theoretical considerations, were realized experimentally, for which purpose the system dichloromethane/diethylene glycol/bisphenol-A polycarbonate was chosen. The pulsating sieve-bottom column was replaced by a nonpulsating column filled with glass beads. In this manner, the number of theoretical plates could be raised considerably. A further improvement of the fractionation efficiency results from the reflux of part of the polymer contained in the sol phase. In praxi, this situation was realized by putting a condensor on top of the column and introducing the feed somewhere near its upper third. After predictive calculations and orienting experiments, 125 g of a polycarbonate with Mw = 29 kg/mol and a nonuniformity U = 1.3 were fractionated in four consecutive CPF runs (where the gels were directly used as feed for the next step) into five fractions of approximately equal weight. Except for the lowest-molecular-weight fraction, one obtains nonuniformities on the order of 0.1.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1992.070450715
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  • 3
    Electronic Resource
    Electronic Resource
    Abbau von polystyrol in cyclohexanlösung bei kleiner schergeschwindigkeit (1973)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 164 (1973), S. 353-355 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1973.021640133
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  • 4
    Electronic Resource
    Electronic Resource
    Pressure dependence of viscometric relaxation times measured with a new apparatus. Williams-Landel-Ferry behaviour of moderately concentrated solutions of poly(butyl methacrylate)s in 2-propanol (1991)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 165-176 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new rotational viscometer is presented which can be operated up to 2 000 bar and a maximum shear stress of 420 Pa. It allows, for the first time, to investigate the non-Newtonian flow behaviour of moderately concentrated polymer solutions. Results of measurements with two representatives of the system 2-propanol/poly(butyl methacrylate) with weight-average molecular weights M̄w = 520 000 and M̄w = 2 050 000, and ratios of weight- to number-average molecular weights M̄w/M̄n = 1,08 and M̄w/M̄w = 1,23, resp. in the region of moderate polymer concentrations are reported. For a ca. 7 wt.-% solution of the higher-molecular-weight polymer one obtains viscometric relaxation times τ0 varying from 1 to 100 ms in the region from 1 to 2 000 bar and from 40 to 75°C; at the lower temperature the application of p can raise τ0 by one order of magnitude. The steady-state shear compliance (proportional to τ0/η0, where η0 is the zero-shear viscosity), is independent of pressure of varies only slightly. For the present system, which gels thermoreversibly upon cooling, η0 and τ0 as a function of temperature and pressure can be well represented by the Williams-Landel-Ferry equation.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1991.021920115
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  • 5
    Electronic Resource
    Electronic Resource
    Sedimentation of dissolved macromolecules in the terrestrial gravitational field near the critical locus (1972)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 161 (1972), S. 277-284 
    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: Die vorliegende Arbeit zeigt sowohl theoretisch als auch experimentell, daß das Schwerefeld der Erde unter annähernd kritischen Bedingungen ausgeprägte Veränderungen in der Gleichgewichtskonzentration von gelösten Makromolekülen mit der Höhe hervorruft.So wurde für das System Polystyrol/Cyclohexan beobachtet, daß die Gleichgewichtskonzentration unter derartigen Bedingungen am Boden eines Gefäßes etwa das Dreifache beträgt wie in 10 cm Höhe. Im Falle polymolekularer Proben ist die Sedimentation von einer entsprechenden Fraktionierung begleitet.
    Notes: The present paper demonstrates theoretically as well as experimentally, that the gravitational field of the earth produces very pronounced changes in the equilibrium concentration of dissolved macromolecules with height, under near critical conditions.Thus it could be observed for the system polystyrene/cyclohexane that the equilibrium concentration at the bottom of a tube is approximately three times that at a height of 10 cm, under such conditions. In the case of polymolecular samples the sedimentation is associated with a corresponding fractionation.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1972.021610120
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  • 6
    Electronic Resource
    Electronic Resource
    True cosolvency. Acetone/diethylether/polystyrene (1973)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 173 (1973), S. 241-245 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1973.021730118
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  • 7
    Electronic Resource
    Electronic Resource
    Large scale fractionation of polyethylene by means of the continuous polymer fractionation (CPF) methodAffectionately dedicated to Prof. W. Burchard on the occasion of his 60th birthday (1990)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 659-670 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The countercurrent extraction method recently developed for the continuous polymer fractionation (CPF) was applied to linear polyethylene (M̄w = 55 kg/mol; M̄n = 16,7 kg/mol). At temperatures higher than 130°C, moderately concentrated solution of polyethylene were extracted to remove the low-molecular-weight components. Discontinuous fractionation experiments served to detect the best suited solvents. Diphenyl ether was chosen to demonstrate that the present extraction can be performed even with the same single solvent used to prepare the feed. For very high-molecular-weight polymers, mixed solvents are, however, normally better than single ones, since they allow an easier tailoring of thermodynamic conditions, and yield much less viscous solutions. Mixtures of tetralin and triethylene glycol turned out to be best suited for polyethylene. By means of four successive CPF runs with the single solvent, polyethylene fractions with non-uniformities U = (M̄w/M̄n) - 1 of approx. 0,3 to 0,4 were obtained on a 100 g scale. The rule of thumb that U can be halved in each CPF step without extensive optimization of the method was corroborated.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1990.021910321
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  • 8
    Electronic Resource
    Electronic Resource
    Pressure and solvent influences on the shear thinning behavior of moderately concentrated solutions of poly(butyl methacrylate) (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 1387-1395 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The viscosities of moderately concentrated solutions of poly(butyl methacrylate) - M̄w = 1820 kg/mol-in the thermodynamically good solvent toluene and in the theta solvent 2-propanol were measured up to pressures of 2000 bar as a function of shear rate \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} in the temperature interval from 40 to 70°C. Both systems obey Graessley's equation so that it is possible to obtain the following rheological parameters in addition to the zero-shear viscosity η0 from the dependences \documentclass{article}\pagestyle{empty}\begin{document}$ \eta (\dot \gamma ) $\end{document}. η can be split into an entanglement part ηent plus a frictional contribution ηfric, and the characteristic viscometric relaxation time τ0 becomes accessible. The present results demonstrate that the application of pressure raises the above parameters much less for good than for bad solvents. In contrast to ηfric (which can react differently to the application of pressure due to special circumstances) η0 and τ0 are always influenced to the same degree as T or p are changed. This result implies that the steady state shear compliance (τ0/η0) is independent of the variables of state irrespective of the thermodynamic quality of the solvent. For the good solvent the effects of temperature can be described by the Arrhenius equation, whereas the WLF equation has to be used for the bad one.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1993.021940513
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  • 9
    Electronic Resource
    Electronic Resource
    Shear influence on the phase separation of oligomer blends (1994)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 195 (1994), S. 1257-1271 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Shear influences on the phase separation behaviour of four different blends of ethylene glycol/propylene glycol oligomers, exhibiting upper critical solution temperatures, were investigated. Cloud point curves at rest (turbidity measurements) are reported for all systems, spinodal conditions (light scattering) and tie-lines (analysis of the coexisting phases) are given for some examples. Phase diagrams under shear were obtained from rheological data. They demonstrate that the demixing temperatures of systems where both glycols bear OH end-groups are lowered up to ca. 1°C by shear rates of 1000s-1; the critical composition, generalized to the non-equilibrium conditions of flow, is markedly shifted. These observations are explained in terms of the generalized Gibbs energy (containing the mechanical energy the system stores during flow) as a consequence of the strongly interacting end-groups of the glycols. This interpretation is backed by the fact that the shear effects disappear when the glycols are methylated.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1994.021950412
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  • 10
    Electronic Resource
    Electronic Resource
    Intramolecular interaction of chain molecules: Second osmotic virial coefficients and intrinsic vicosities (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 1491-1504 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In a new theoretical approach the separation of a pair of chain molecules (measured thermodynamically by the second osmotic virial coefficient A2) is treated as a two-step process: In the first step the molecules are detached from each other by the addition of solvent - keeping their dimensions constant - and in the second step the now isolated coils are allowed to relax into their equilibrium dimensions. For the description of the second step, in which only segments belonging to one molecule take part, an intra-molecular interaction parameter is introduced on the basis of the intrinsic viscosity. The present two-parameter approach yields A2 = A2∞ + σ M-(1-a) for the dependence of A2 on the molecular weight M of the polymer; a is the exponent of the Kuhn-Mark-Houwink equation and σ a parameter measuring the effects associated with the second step (becoming zero if the coil dimensions do not depend on polymer concentration). A test of the above relation by means of published material demonstrates its superiority over other two parameter theories: It can describe the actually measured A2(M) well down into the region of oligomers without an additional parameter and it comprises the conceptual advantage of explaining experimental observations concerning ∂A2/∂M 〉 0 or ∂A2/∂M ≈ 0 for high A2 values.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1993.021940523
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