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1

Digitale Medien

Theory-based improvements of continuous polymer fractionation demonstrated for poly(carbonate) (1992)

Weinmann, K. ; Wolf, B. A. ; Rätzsch, M. T. ; [weitere]

New York, NY [u.a.] : Wiley-Blackwell

Journal of Applied Polymer Science 45 (1992), S. 1265-1279

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ISSN: 0021-8995

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: 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.

Zusätzliches Material: 11 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/app.1992.070450715

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2

Digitale Medien

Thermal fractionation and identification of low-density polyethylenes (1996)

Wolf, B. ; Kenig, S. ; Klopstock, J. ; [weitere]

New York, NY [u.a.] : Wiley-Blackwell

Journal of Applied Polymer Science 62 (1996), S. 1339-1345

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ISSN: 0021-8995

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: In the present publication, a method to identify and distinguish between different types of low-density polyethylene based on thermal fractionation and FTIR analysis is described. It was shown that during thermal fractionation four to seven endothermic peaks are obtained as opposed to one or two peaks obtained during regular differential scanning calorimetric analysis. The ration between band heights at 1368 and 1376 cm-1 was found to represent the length of the side chain (branch). © 1996 John Wiley & Sons, Inc.

Zusätzliches Material: 7 Ill.

Materialart: Digitale Medien

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3

Digitale Medien

Comment on the novel parameter of polymer structure suggested by W. S. Bahary (1968)

Wolf, B. A.

New York, NY [u.a.] : Wiley-Blackwell

Journal of Applied Polymer Science 12 (1968), S. 973-974

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ISSN: 0021-8995

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/app.1968.070120430

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4

Digitale Medien

Continuous fractionation and solution properties of PIB.Part I: cf. Ref. 1. II. CPF optimization (1987)

Geerissen, H. ; Schützeichel, P. ; Wolf, B. A.

New York, NY [u.a.] : Wiley-Blackwell

Journal of Applied Polymer Science 34 (1987), S. 287-305

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ISSN: 0021-8995

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: The quality of polymer fractionation depends on the choice of the mixed solvent as well as on the particular conditions of operating the continuous countercurrent extraction. With a polyisobutylene (PIB) sample of medium molecular weight Mw = 98,400 g/mol and U = (Mw/Mn) - 1 = 1.4 plus the mixed solvents toluene/2-butanone (TOL/MEK) and n-heptane/2-butanone (HEP/MEK) (both giving comparably good fractionation in equilibrium experiments), possible ways to optimize the CPF were tested. The mixed solvent HEP/MEK turns out to be superior to TOL/MEK for kinetic reasons. Due to the larger gap between its density and that of the pure polymer, the coexisting phases can still move through the column, even if the working point of the CPF is chosen close to the consolute point of the ternary system. Under these conditions the mass transfer becomes more rapid, and up to 80% of the (mixed) solvent can be economized as compared with TOL/MEK. Four CPF runs with TOL/MEK (each dividing the polymer material into portions approximately equal in weight, and rejecting the first low molecular fraction) yielded four 200 g samples of Mw ranging from 80,600 to 257,000 with U values of ca. 0.3.

Zusätzliches Material: 13 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/app.1987.070340124

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5

Digitale Medien

Continuous fractionation and solution properties of PIB. I. Search for the best mixed solvent and first results of the continuous polymer fractionation (1987)

Geerissen, H. ; Roos, J. ; Schützeichel, P. ; [weitere]

New York, NY [u.a.] : Wiley-Blackwell

Journal of Applied Polymer Science 34 (1987), S. 271-285

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ISSN: 0021-8995

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: To adopt a recently developed method for large scale fractionation (CPF = continuous polymer fractionation, a special kind of counter current extraction) to polyisobutylene (PIB), a systematic search for the best mixed solvent was performed. For this purpose, the essential parts of the phase diagrams solvent/nonsolvent/PIB were determined for 21 mixed solvents by cloud-point measurements; with eight systems of special interest, the molecular weight distributions of the polymers contained in the coexisting phases were also studied. On the basis of these experiments and of considerations concerning additional criteria for the performance of the continuous counter current extraction, the mixed solvent toluene/methyl ethyl ketone was chosen. First experiments with a PIB sample of Mw = 420,000 g/mol and a molecular nonuniformity U = (Mw/Mn) - 1 of 2.3 yielded two high molecular weight fractions Mw = 1.1 × 106 and 0.6 × 106 resp., with U = 0.3 on a 100 g scale upon the application of four CPF steps.

Zusätzliches Material: 9 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/app.1987.070340123

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6

Digitale Medien

On the factors governing the pressure dependence of the viscosity of moderately concentrated polymer solutionsPart of theses of H. G. and J. R. S. (1982)

Geerissen, H. ; Schmidt, J. R. ; Wolf, B. A.

New York, NY [u.a.] : Wiley-Blackwell

Journal of Applied Polymer Science 27 (1982), S. 1277-1291

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ISSN: 0021-8995

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: Viscosity measurements were carried out as a function of pressure and temperature with solutions of polystyrene in eight (endothermal) θ-solvents at the respective critical composition by means of a Searle-type apparatus. A rolling-ball viscometer was used for the investigation of the pure solvents. In all cases the viscosity coefficient increases in a more or less exponential manner when the pressure is raised. For θ-conditions, the volumes of activation of the solutions exceed that of the pure solvent by typically 10-15%. The exact amount of this extra efffect stemming from the presence of the polymer and its variation with temperature can be qualitatively correlated with the heats of mixing. The ratio of the viscosity of the solution at 1000 and 1 bar, respectively, can be varied for a given solvent power (θ-temperature) by the choice of the solvent from ca. 2 (cyclopentane) to 4 (trans-decalin). Within a given system, the maximum effects that can be realized by a change of the solvent power via the variation of temperature ranges from ca. 3 to 6 (tert-butylacetate).

Zusätzliches Material: 14 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/app.1982.070270417

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7

Digitale Medien

Sedimentation of dissolved macromolecules in the terrestrial gravitational field near the critical locus (1972)

Wolf, B. A.

New York : Wiley-Blackwell

Die Makromolekulare Chemie 161 (1972), S. 277-284

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ISSN: 0025-116X

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Beschreibung / Inhaltsverzeichnis: 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.

Notizen: 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.

Zusätzliches Material: 3 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/macp.1972.021610120

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8

Digitale Medien

Die viskosität von polymerlösungen in der nähe von oberen und unteren entmischungstemperaturen (1977)

Rigler, J. K. ; Wolf, B. A. ; Breitenbach, J. W.

Weinheim : Wiley-Blackwell

Angewandte Makromolekulare Chemie 57 (1977), S. 15-27

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ISSN: 0003-3146

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Beschreibung / Inhaltsverzeichnis: The viscosity of liquid mixtures exhibits a characteristic temperature dependence near the consolute point. For polymer solutions this phenomenon is well studied in the case of upper critical solution temperatures, whereas no such measurements exist in the vicinity of lower critical solution temperatures.Viscosity measurements were performed for the system cyclohexane/polystyrene (upper critical solution temperature) and for the system orthotrimethylformiate/diethylether/polystyrene (lower critical solution temperature). For the former system qualitative agreement with. the results of Debye and coworkers was found. The investigations in the vicinity of the lower critical solution temperatures also disclosed that an additional function is superimposed to the normal temperature dependence of the viscosity which leads to an increase in viscosity before demixing sets in. This behaviour can be described by an equation analogous to that used for lower solubility gaps.

Notizen: Die Viskosität flüssiger Mischungen zeigt in der Nähe des kritischen Entmischungspunktes eine charakteristische Temperaturabhängigkeit. für Polymerlösungen ist diese Erscheinung bei der oberen kritischen Entmischungstemperatur gut untersucht, während in der Umgebung der unteren kritischen Entmischungstemperatur keine derartigen Messungen vorliegen.ES wurden Viskositätsmessungen im System Cyclohexan/Polystyrol (obere kritische Entmischungstemperatur) und im System Orthotrimethylformiat/Diäthyläther/Polystyrol (untere kritische Entmischungstemperatur) durchgeführt. Beim ersten System ergab sich qualitative Übereinstimmung mit den Ergebnissen von Debye und Mitarbeitern. Die Untersuchungen in der Umgebung der unteren kritischen Entmischungstemperatur zeigten, daß auch hier dem normalen Viskositäts-Temperaturverlauf eine zusätzliche Funktion überlagert ist, die zu einem Viskositätsanstieg vor Eintritt der Entmischung führt. Dieses Verhalten läßt sich mit einer analogen Gleichung beschreiben, wie sie für untere Mischungslücken verwendet wurde.

Zusätzliches Material: 7 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/apmc.1977.050570102

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9

Digitale Medien

Interdependence of enthalpic and entropic contributions to the second osmotic virial coefficient (1972)

Wolf, B. A.

New York : Wiley-Blackwell

Journal of Polymer Science Part A-2: Polymer Physics 10 (1972), S. 847-856

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ISSN: 0449-2978

Schlagwort(e): Physics ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: The interdependence of the enthalpic contribution A2, H and the entropic contribution A2, s to the second osmotic virial coefficient for a given polymer-solvent system has been investigated from the experimental and the theoretical point of view. Experimentally, the following common facts were observed for various systems at temperatures and pressures below the critical values for the solvent. Both the isobaric and isothermal dependences can be approximated over relatively wide ranges of A2, H by linear relations with a slope deviating only slightly, but in a characteristic manner from a value of -1. When the temperature is increased at constant pressure one moves along an isobar towards higher A2, H; when the pressure is increased at constant temperature, one moves along an isotherm in the opposite direction, i.e., towards lower A2, H. Theoretically this behavior can be described in a qualitative manner, starting from a relation derived by Patterson and Delmas on the basis of the Prigogine corresponding-states theory. The reasons for the lack of quantitative agreement are discussed.

Zusätzliches Material: 4 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1972.160100506

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10

Digitale Medien

Measured and calculated solubility of polymers in mixed solvents: Co-nonsolvencyDedicated to Professor Dr. J. W. Breitenbach in honor of his 70th birthdayAfter submission of this paper Professor Dr. J. W. Breitenbach deceased on 6. 1. 1978. (1978)

Wolf, B. A. ; Willms, M. M.

New York : Wiley-Blackwell

Die Makromolekulare Chemie 179 (1978), S. 2265-2277

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ISSN: 0025-116X

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: The phenomenon of co-nonsolvency, i.e. the formation of nonsolvents by mixing two solvents, was studied for the system N,N-dimethylformamide/cyclohexane/polystyrene (DMF/CH/PS) which is characterized by the fact that the components of the mixed solvent are only incompletely miscible below 48,6°C. A number of quasibinary sections (stepwise addition of the second solvent to given solutions of the polymer in the first solvent) for a sample (M = 110000) of high molecular uniformity yielded a cloud point surface which gives “island curves” (closed solubility gaps) for constant temperatures between the critical temperature of DMF/CH and the top of the cloud point surface (51,3°C). The attainment of equilibrium is facilitated by the addition of DMF to CH or solutions of PS in CH, as compared with the opposite procedure. By means of phase equilibrium experiments tie lines and the critical curve could also be constructed. For a theoretical calculation of the latter from information concerning the binary sub-systems (e.g. light scattering of PS in DMF) the single liquid approximation was applied to DMF/PS instead of - with respect to miscibility - the more dissimilar DMF/CH; the results are in qualitative accord with experimental observations. Orienting measurements concering the chain length dependence of the partition coefficient in co-nonsolvent systems indicate that their aptitude for fractionation is considerably worse than that of normal systems under comparable conditions.

Zusätzliches Material: 11 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/macp.1978.021790914

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