ZIB

1

Digitale Medien

Rheooptical study of isotropic solutions of stiff polymers (1990)

Mead, D. W. ; Larson, R. G.

s.l. : American Chemical Society

Macromolecules 23 (1990), S. 2524-2533

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 1520-5835

Quelle: ACS Legacy Archives

Thema: Chemie und Pharmazie , Physik

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1021/ma00211a021

Permalink

Bibliothek	Standort	Signatur	Band/Heft/Jahr	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

2

Unbekannt

FLOODS AND FAMINE IN CHINA. (1915)

Mead, D. W.

Macomb, Ill., etc. : Periodicals Archive Online (PAO)

Journal of Geography. 14 (1915/1916) 261

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0022-1341

Thema: Geographie

URL: http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pao:&rft_dat=xri:pao:article:1129-1915-000-00-000080

Permalink

Bibliothek	Standort	Signatur	Band/Heft/Jahr	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

3

Digitale Medien

A parallel-plate rheometer for the measurement of steady-state and transient rheological properties (1983)

Liu, T. Y. ; Mead, D. W. ; Soong, D. S. ; [weitere]

Springer

Rheologica acta 22 (1983), S. 81-89

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 1435-1528

Schlagwort(e): Rheometer ; transient stress ; parallel plate ; shear properties

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie , Physik

Notizen: Abstract A parallel-plate rheometer (PPR) has been constructed for use with the Materials Test System (MTS) for the measurement of fast transient and steady-state responses of polymeric liquids. This particular combination exploits the versatility and capability of the MTS programmable drive system, while the design of the PPR ensures the ideal simple shearing configuration. Instrument compliance, material inertia and mechanical lag in both the input and output components of the system are minimal, thus avoiding defects of most existing rheometers. Reproducible data on a 20% polyisobutylene-in-decalin solution have been obtained for various complicated flow programs. This test system is thus suitable for extensive rheological characterization of complex viscous liquids.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01679832

Permalink

Bibliothek	Standort	Signatur	Band/Heft/Jahr	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

4

Digitale Medien

The reptation model with segmental stretch (1995)

Mead, D. W. ; Yavich, D. ; Leal, L. G.

Springer

Rheologica acta 34 (1995), S. 360-383

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 1435-1528

Schlagwort(e): Steady state planar flows ; tube model ; constitutive equation ; universal tensor

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie , Physik

Notizen: Abstract Numerical predictions of the Doi-Edwards tube model with segmental stretch and a freely jointed chain spring model are presented for steady two-dimensional flows with a continuously varying degree of extensional and shear character. Our results are obtained from three sets of calculations by considering the effect of the flow-type parameter, the molecular weight and the number of entanglements per chain on the model predictions. The predicted degree of stretch and orientation, as well as specific rheological and optical properties that can be measured experimentally are presented. As anticipated, calculations reveal that the ‘orientational’ dynamics are controlled by the reptative tube disengagement process, whereas the stretching process is controlled by the Rouse dynamics. Inclusion of segmental stretch fundamentally alters the character of the Doi-Edwards model. Calculations reveal that as the flow becomes increasingly extensional in character, significant steady state stretch is predicted with a commensurate modification of the material functions. According to calculated results, it is possible to have significant chain stretching without producing measurable changes in the stress optical coefficient.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00367152

Permalink

Bibliothek	Standort	Signatur	Band/Heft/Jahr	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

5

Digitale Medien

The reptation model with segmental stretch (1995)

Mead, D. W. ; Leal, L. G.

Springer

Rheologica acta 34 (1995), S. 339-359

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 1435-1528

Schlagwort(e): Tube model ; segmental stretch ; constitutive equation ; molecular model

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie , Physik

Notizen: Abstract The Doi-Edwards model with segmental stretch and a non-linear finitely extensible spring law is described and examined in simple flow situations where analytic results are derivable; namely oscillatory flow and steady state flow at high deformation rates. The model is shown to be consistent with the Bueche-Ferry hypothesis in fast large strain unidirectional flows but to violate this rule in small strain reversing flows. The discrepancy is identified with a preaveraging approximation used to describe the relative tube-chain velocity. Experimentally verifiable scaling rule for the birefringence as a universal function of a planar flow-type parameter and deformation rate are identified. Sensitivity to the extensional flow character, absent in the original tube model, manifests itself with the introduction of segmental stretch. Although the model generates a non-separable memory function kernel the deformation dependence of the memory function is quantitatively shown to have negligible impact on the predicted theological properties relative to the original Doi-Edwards model. With this simplification, relatively uncomplicated approximations to the segmental stretch model can be deduced.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00367151

Permalink

Bibliothek	Standort	Signatur	Band/Heft/Jahr	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

6

Digitale Medien

Evolution of the molecular weight distribution and linear viscoelastic rheological properties during the reactive extrusion of polypropylene (1995)

Mead, D. W.

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

Journal of Applied Polymer Science 57 (1995), S. 151-173

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0021-8995

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: Homogeneous and nonhomogeneous reactive extrusion of polypropylene is modeled using random chain scission statistics coupled with the double reptation mixing rule. In this manner, the evolution of both the molecular weight distribution and the linear viscoelastic material properties is quantitatively predicted for the reactive extrusion-pelletization process. Dispersion in the level of random chain scission has little impact on the MFI for a given average level of chain scission; however, dispersion does generate a marked increase in the recoverable compliance (melt elasticity) relative to the ideal homogeneous random chain scission case. Methods to quantitatively determine the degree of cracking dispersion in processing equipment are identified. Quality control issues such as blending materials of known linear viscoelastic properties to obtain a desired property set is considered in the context of known empirical relations consistent with the double reptation model. Simple mixing rules for the melt flow index and the steady-state recoverable compliance involving only single component MFI and Je information are derived. © 1995 John Wiley & Sons, Inc.

Zusätzliches Material: 17 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/app.1995.070570205

Permalink

Bibliothek	Standort	Signatur	Band/Heft/Jahr	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext

7

Digitale Medien

Toward a quantitative theory of the rheology of concentrated solutions of stiff polymers (1991)

Larson, R. G. ; Mead, D. W.

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part B: Polymer Physics 29 (1991), S. 1271-1285

zur Merkliste hinzufügen auf der Merkliste

Details

ISSN: 0887-6266

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: Predictions of the rheological properties of concentrated isotropic solutions of stiff polymers are made that improve on those obtained with the approximate Doi theory. Predictions of the shear-rate and concentration dependence of the viscosity η and the first and second normal stress differences N1 and N2 that avoid the closure approximations of Doi are obtained by using a Galerkin numerical solution for the orientation distribution function. The predictions for η and N1, though they neglect the effects of polydispersity in molecular weight, are shown to be in quantative agreement with recent measurements on solutions of poly-γ-benzyl-L-glutamate (PBLG). The polydispersities of a series of commercial PBLG and PBDG samples are measured by gel permeation chromatography, and found to be broad. An attempt is made to account for the effects of polydispersity on the linear viscoelastic storage and loss moduli for PBLG solutions by using the Marrucci-Grizzuti extension of the Doi theory. The attempt fails. The most probable explanation for the failure is that the rotary diffusive motions of the shorter molecules in the mixture are drastically slowed by the matrix of surrounding longer molecules.

Zusätzliches Material: 15 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/polb.1991.090291011

Permalink

Bibliothek	Standort	Signatur	Band/Heft/Jahr	Verfügbarkeit

Andere fanden auch interessant ...

Artikel (Nationallizenzen)

Volltext