ISSN:0005-9021    

DOI:10.1002/bbpc.19790830402

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1979

数据来源: WILEY

摘要:

AbstractGas sorption and transport in amorphous polymers above their glass transition temperature are adequately described phenomenologically by Henry's and Fick's laws. However, below the glass transition temperature an additional sorption mechanism develops which follows the Langmuir isotherm, and, thus, there are two populations of gas molecules which may be regarded to be in equilibrium with each other. The Langmuir mechanism evidently arises from the non‐equilibrium nature of the glassy state. Molecules sorbed by this mechanism have less diffusional mobility than molecules sorbed by the Henry's law mode. Because of these differences, the analyses of transient permeation experiments are more complex for glassy polymers compared to those used widely for rubbery polymers. A more comprehensive phenomeno‐logical model for transport of gases in glassy polymers is developed here which has been successfully used to interpret the observed dependence of the permeability coefficient and diffusion time lag on upstream gas pressure. The state of knowledge about gas sorption and transport in glassy polymers is reviewed and contrasted with that of rubbery polymers. It is seen that such observations provide a unique method to probe the physical structure of the glassy state and that knowledge in this area is increasing rapi

ISSN:0005-9021    

DOI:10.1002/bbpc.19790830403

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1979

数据来源: WILEY

摘要:

AbstractDiffusion in semi‐crystalline polymers and polymer networks often generates crystallization or dissolution processes or changes in the conformation of the network chains so that the diffusion mostly cannot be described by the Fickian law (“Non‐Fickian” diffusion). To discuss the local change of polymer conformation the flux of diffusion has to be transformed in the polymer‐fixed reference frame. Different constraints including diffusion induced anisotropic states and decoupled processes in this reference frame generate a steady state of the total flux of diffusion of solvent molecules even in infinite extended systems. This steady state diffusion is consistent with a two‐dimensional diffusion process in the polymer‐fixed re

ISSN:0005-9021    

DOI:10.1002/bbpc.19790830404

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1979

数据来源: WILEY

摘要:

AbstractDie Kinetik des Auflösungsprozesses eines polymeren Stoffes in einem strömenden Lösungsmittel wird von thermo‐ und hydrodynamischen Eigenschaften des Polymer‐Lösungsmittel‐Systems beeinflußt. Es können verschiedene Mechanismen unterschieden werden:1Normale Auflösung: Die Auflösungsgeschwindigkeit wird durch gegenseitige Diffusion der Komponenten innerhalb einer Quellschicht gesteuert.2Auflösung ohne Quellschicht: Unterhalb der Geltemperatur wird der Auflösungsprozeß durch eine behinderte Konformationsumwandlung der Makromoleküle vom Glas‐ in den Gleichgewichtszustand kontrolliert.3Auflösung mit Entmischung in der Quellschicht: Die Quellschicht zerfällt in Gel‐ und Solschicht. Der Lösungsprozeß verläuft nicht‐stationär.4Auflösung mit Rekristallisation in der Quellschicht: Die Auflösung von glasigen, aber kristallisationsfähigen Polymeren (Beispiel: Polycarbonat) führt zu einer quasistationären Kristallisationszone innerhalb der Quellschicht.5Auflösung von teilkristallinen Polymeren: Die Wachstumsbedingungen der sphärolithischen Struktur sind für den Löseprozeß geschwindigkeitsbestimmend.Der Auflösungsprozeß hat in der Röntgen‐Lithographie große Bedeutung. Zur Abbildung kleinster Strukturen wird ein Polymer‐Resist durch Strahlung partiell abgebaut und mit einem Lösungsmittel selektiv entwickelt. ‐ Das Ausmaß der Strahlenschädigung im Polymerresist kann ü

ISSN:0005-9021    

DOI:10.1002/bbpc.19790830405

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1979

数据来源: WILEY

摘要:

AbstractIm Temperaturbereich von 25 °C bis 90 °C wurden die Sorptionsisothermen und Diffusionskoeffizienten von Acrylnitril in Polyacrylnitril‐pulver ermittelt. Die Sorption läßt sich durch nicht‐lineare Isothermen kennzeichnen, die Diffusion ist durch sehr kleine Diffusionskoeffizienten bestimmt (25 °C: D = 4 · 10−16cm2/s; Aktivierungsenergie 67.7 kJ/mol). Durch eine gleichzeitig mit der Eindiffusion beobachtete Adsorption von Acrylnitril an der Polyacrylnitril‐Oberfläche bedingt konnte eine Abschätzung des freien Volumens im verwendeten Pulver zu 1,8% vor

ISSN:0005-9021    

DOI:10.1002/bbpc.19790830406

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1979

数据来源: WILEY

摘要:

AbstractThe change of the racial structure during the diffusion of dyestuffs in fibres of poly(ethylene terephthalate), [poly(oxyethylenoxytere‐phthaloyl)], is studied with regard to the relationship between the dyestuff diffusion and the structure of high polymers. The fibre structure is described by interferometric measurements, which allow statements about order and orientation as a function of the diffusion path. The experimental results show that C. I. Disperse Red 60 raises the parameters which describe the order and orientation and that C. I. Disperse Blue 139 lowers these structure parameters. — An interpretation of concentration distributions of dyestuffs in microtomic cuttings gives informations about the diffusion process. It is shown, that the diffusion of dyestuffs in high polymers depends — in a complicated way ‐ on fibre structure (as a function of the diffusion path), fibre history and experimental conditions: C. I. Disperse Red 60 shows a lower diffusion rate at higher radial orientations, whereas the diffusion rate of C.I. Disperse Blue 139 does not depend on the radial dependence of these structure par

ISSN:0005-9021    

DOI:10.1002/bbpc.19790830407

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1979

数据来源: WILEY

摘要:

AbstractDiffusion is a very fundamental phenomenon which plays an important role in the most varied physical and chemical processes. In living matter, in industrial production, in material science it is in many cases basic to our understanding of what happens. Often the systems of interest are macromolecular in nature: the “solute” or the “solvent” or both may consist of big molecules. Very often the concentrations are high and sometimes the system is in a condition close to phase separation. Not unfrequently there may be more than one solute component present. ‐ Against this background some more recent results will be reviewed and discussed especially concerning diffusion and self‐diffusion in more concentrated solutions, the frictional coefficient and its concentration dependence, the diffusion behaviour of systems close to a critical point of mixing, diffusion under conditions where reactions (e.g. aggregation or dissociation) occur and in multicomponent systems. Some newer experimental techniques which have influenced the recent development will be briefl

ISSN:0005-9021    

DOI:10.1002/bbpc.19790830408

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1979

数据来源: WILEY

摘要:

AbstractTransport from the liquid phase through homogeneous polymeric membranes has several features that distinguish it from gas and vapour permeation. The concentration of permeant in the polymer is usually high and has a large influence on diffusion coefficients. The driving force for transport, the gradient of chemical potential of the liquid, may be controlled by the application of a pressure but the functional form of the dependence of chemical potential on pressure is different in a liquid from that which applies in gas diffusion. Frequently the chemical potential gradients in liquid transport are small. ‐ The driving force may also be controlled by varying the composition of the liquid phases i. e. by setting up an osmotic pressure difference across the membrane. This can only be done with systems of more than one component and the study of transport from the liquid phase therefore leads readily into the study of several simultaneous fluxes and the possibilities of membrane selectivity and separation. ‐ This paper reviews work on the mechanisms of steady flow of, principally, organic liquids through polymer membranes under pressure from the liquid phase into either another liquid phase, as in hyperfiltration, or into a vapour phase as in pervaporation. The transport of a single liquid is considered first Then the flow of binary liquid mixtures is discussed and the mechanisms of separations or organic liquids by hyperfiltration and pervaporation are exami

ISSN:0005-9021    

DOI:10.1002/bbpc.19790830409

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1979

数据来源: WILEY

摘要:

AbstractAn den Beispielen, Mehrschichtfolien, Kunststoffschäume und Polymergemenge, werden Anwendungsmöglichkeiten von Diffusions‐, Löslichkeits‐ und Permeationswerten auf Probleme der Praxis aufgezeigt. Bei Mehrschichtfolien wird die Schicht mit der geringsten Permeablität für die Sperreigenschaften der Kombination bestimmend, hingegen wird bei Polymergemengen das Eigenschaftsbild durch die kohärente Phase dominierend beeinflußt. Bei “ verpackten” Kunststoffen, das sind Polymergemenge, bei denen die kohärente Phase nur einen kleinen Gewichtsanteil der Gesamtprobe ausmacht und in Polyederstruktur vorliegt, wird die Phase in Überschuß wie die Gaskomponente in einem geschlossenzelligen Schaum verpackt. Sowohl in solchen Gemengen als auch in Schäumen wird die kohärente Polyederphase eigenschaftsbestimmend. Für die Biomedizin sind Polymergemenge aus Polyelektrolyten mit sehr spezifischer Morphologie von Interesse. Über ihr Quell‐ und Permeationsverhalten schlagen sie eine Brücke zu den Biomembranen, so daß die Behauptung, daß Diffusion, Löslichkeit und Permeation niedrigmolekularer Verbindungen in Polymeren lebensnotwendig

ISSN:0005-9021    

DOI:10.1002/bbpc.19790830410

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1979

数据来源: WILEY

摘要:

AbstractDiffusion coefficients of different polyvinylchloride (PVC)‐samples have been measured in solvents of varying quality up to polymer concentrations which were still experimentally tractable. The samples differed by polymerization conditions and thus by the stereospecific microstructure. The thermodynamic factor of the diffusion coefficient was determined osmotically and the mobility of the polymer was calculated. In the semi‐dilute concentration range, the diffusion coefficient does no more depend on the molar mass of the polymer but is strongly influenced by the stereospecific microstructure of the PVC. The concentration dependence of the diffusion coefficients in all systems under investigation can be described by the relationshipD∼ ρα2. This was predicted by a new theory of De

ISSN:0005-9021    

DOI:10.1002/bbpc.19790830411

出版商:Wiley‐VCH Verlag GmbH&Co. KGaA    

年代:1979

数据来源: WILEY