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Titolo:
Creaming and oscillation rheology of weakly flocculated concentrated emulsions
Autore:
Moates, GK; Watson, AD; Robins, MM;
Indirizzi:
Inst Food Res, Norwich NR4 7UA, Norfolk, England Inst Food Res Norwich Norfolk England NR4 7UA h NR4 7UA, Norfolk, England
Titolo Testata:
COLLOIDS AND SURFACES A-PHYSICOCHEMICAL AND ENGINEERING ASPECTS
fascicolo: 1-2, volume: 190, anno: 2001,
pagine: 167 - 178
SICI:
0927-7757(20010930)190:1-2<167:CAOROW>2.0.ZU;2-F
Fonte:
ISI
Lingua:
ENG
Soggetto:
COLLOID-POLYMER MIXTURES; AGGREGATION; BEHAVIOR;
Keywords:
emulsions; creaming; depletion flocculation; delay time; transient gelation;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
16
Recensione:
Indirizzi per estratti:
Indirizzo: Robins, MM Inst Food Res, Norwich Business Pk, Norwich NR4 7UA, Norfolk, England Inst Food Res Norwich Business Pk Norwich Norfolk England NR4 7UA
Citazione:
G.K. Moates et al., "Creaming and oscillation rheology of weakly flocculated concentrated emulsions", COLL SURF A, 190(1-2), 2001, pp. 167-178

Abstract

Addition of the non-adsorbing polymer hydroxyethylcellulose (HEC) to oil-in-water emulsions induces flocculation via the depletion mechanism. In the present work, we report results on the delay time prior to creaming of hexadecane-in-water emulsions, flocculated by HEC. In addition, we report on oscillation rheology measurements of a comparable, density-matched system. Wecompare the two in the search for rheological signatures of delay, and forinsight into the delay mechanism. Our results suggest that the commonly used low-frequency relaxation time does not map simply to delay time. We do, however, find that rheology can tell which of our compositions will exhibitdelay, and which will not. In addition, those compositions having the greatest shear modulus have the longest delay. A simple model, in which the delay is attributed to a slow creaming stage over a very small distance, produces an acceptable correlation with the product of complex viscosity and thestrain at the end of linearity. Thus the area under the linear portion of the complex viscosity-strain plot may provide a useful marker of delay time. The unexpected observation of a liquid-like regime at high oscillation frequency merits further investigation. (C) 2001 Elsevier Science B.V. All rights reserved.

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Documento generato il 04/04/20 alle ore 09:00:10