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Titolo:
Entangled dynamics and melt flow of branched polymers
Autore:
McLeish, TCB; Milner, ST;
Indirizzi:
Univ Leeds, Dept Phys & Astron, IRC Polymer Sci & Technol, Leeds LS2 9JT, W Univ Leeds Leeds W Yorkshire England LS2 9JT & Technol, Leeds LS2 9JT, W Exxon Res & Engn Co, Annandale, NJ 08801 USA Exxon Res & Engn Co Annandale NJ USA 08801 gn Co, Annandale, NJ 08801 USA
Titolo Testata:
BRANCHED POLYMERS II
, volume: 143, anno: 1999,
pagine: 195 - 256
SICI:
0065-3195(1999)143:<195:EDAMFO>2.0.ZU;2-4
Fonte:
ISI
Lingua:
ENG
Soggetto:
STAR POLYMER; WORMLIKE MICELLES; VISCOELASTIC PROPERTIES; LINEAR VISCOELASTICITY; RHEOLOGICAL BEHAVIOR; NEUTRON-SCATTERING; STRESS-RELAXATION; TUBE MODELS; GEL POINT; VISCOSITY;
Keywords:
viscoelasticity; molecular rheology; branched polymers; tube model; non-Newtonian flow;
Tipo documento:
Review
Natura:
Collana
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
93
Recensione:
Indirizzi per estratti:
Indirizzo: McLeish, TCB Univ Leeds, Dept Phys & Astron, IRC Polymer Sci & Technol, Leeds LS2 9JT, W Univ Leeds Leeds W Yorkshire England LS2 9JT eeds LS2 9JT, W
Citazione:
T.C.B. McLeish e S.T. Milner, "Entangled dynamics and melt flow of branched polymers", ADV POLYM S, 143, 1999, pp. 195-256

Abstract

One of the most puzzling properties of branched polymers is their unusual viscoelasticity in the melt state. We review the challenges set by both non-linear experiments in extension and shear of polydisperse branched melts, and by the growing corpus of data on well-characterised melts of star-, comb- and H- molecules. The remarkably successful extension of the de Gennes/Doi-Edwards tube model to branched polymers is treated in some detail in thecase of star polymers for which it is quantitatively accurate. We then apply it to more complex architectures and to blends of star-star and star-linear composition. Treating linear polymers as "2-arm stars" for the early fluctuation-dominate stages of their stress-relaxation successfully accounts for the relaxation spectrum and "3.4-law" viscosity-molecular weight relationship. The model may be generalised to strong flows in the form of molecular constitutive equations of a structure not found in the phenomenological literature. A model case study, the "pom-pom" polymer, exhibits strong simultaneous extension hardening and shear softening, akin to commercial branched polymers. Computation with such a constitutive equation in a viscoelastic flow-solver reproduces the large corner vortices in contraction flows characteristic of branched melts and suggests possible future applications of the modelling tools developed to date.

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Documento generato il 06/08/20 alle ore 23:43:00