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Titolo:
Measurement of apparent extensional viscosities of polyolefin melts from process contraction flows
Autore:
Martyn, MT; Nakason, C; Coates, PD;
Indirizzi:
Univ Bradford, IRC Polymer Sci & Technol, Dept Mech & Med Engn, Bradford BD7 1DP, W Yorkshire, England Univ Bradford Bradford W Yorkshire England BD7 1DP , W Yorkshire, England
Titolo Testata:
JOURNAL OF NON-NEWTONIAN FLUID MECHANICS
fascicolo: 2-3, volume: 92, anno: 2000,
pagine: 203 - 226
SICI:
0377-0257(20000831)92:2-3<203:MOAEVO>2.0.ZU;2-K
Fonte:
ISI
Lingua:
ENG
Soggetto:
POLYMER MELTS; ELONGATIONAL FLOW; POLYETHYLENE MELT; LOW-DENSITY; NUMERICAL-SIMULATION; POLYSTYRENE MELTS; CONVERGING FLOW; STRAIN RATE; BIREFRINGENCE; BEHAVIOR;
Keywords:
extensional viscosity; extensional strain rate; continuum mechanics; flow visualisation;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Engineering, Computing & Technology
Citazioni:
43
Recensione:
Indirizzi per estratti:
Indirizzo: Coates, PD Univ Bradford, IRC Polymer Sci & Technol, Dept Mech & Med Engn,Bradford BD7 1DP, W Yorkshire, England Univ Bradford Bradford W YorkshireEngland BD7 1DP re, England
Citazione:
M.T. Martyn et al., "Measurement of apparent extensional viscosities of polyolefin melts from process contraction flows", J NON-NEWT, 92(2-3), 2000, pp. 203-226

Abstract

The extensional characteristics of branched and linear polyolefin melts have been evaluated in slit die flow cells with abrupt contraction ratios of 4:1 and 15:1 on a single screw extruder Apparent extensional viscosities ofthe melts in planar flows have been obtained by two routes, the first employing extensional strain rate data measured from particle velocimetry, the second using a continuum mechanics analysis based on the entry flow profile. The influence of flow geometry on apparent extensional viscosity of the polymer melts has been investigated. The measured in-process apparent extensional viscosities of the branched and Linear polyolefin melts are found to be in good agreement, despite differences in the strain histories imposed by two contraction geometries (centre line extensional stress and corresponding average axial strain rates differ). Particle velocimetry was found to be better than the continuum mechanics approach in obtaining extensional strain rates due to a lower susceptibility to experimental errors. It appears that the in-process methods of assessing apparent extensional viscosity, with an abrupt 180 degrees entry slit die, are geometry independent for the range of materials, strain and strain rates covered and provide a useful technique for ranking process-typical extensional behaviour of melts. (C) 2000Elsevier Science B.V. All rights reserved.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 29/11/20 alle ore 03:34:56