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Shear Thinning Behavior of Concentrated Latex Dispersions
Author(s) -
Takamura Koichi,
de Ven Theo G. M. van
Publication year - 2010
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.201050210
Subject(s) - shear rate , materials science , volume fraction , shear thinning , colloid , dispersity , viscosity , shear (geology) , composite material , polymer chemistry , chemistry , organic chemistry
Summary: Measured viscosity vs . shear rate relationships were analyzed for a wide variety of carboxylated latexes reported in the literature using the theoretical model proposed by one of the authors. The theory contains three main parameters: c m , k o and δ , which are the maximum volume fraction, a particle interaction parameter closely related to the secondary electroviscous effect, and the thickness of the stabilizing surface layer, respectively. It is assumed that sheared dispersions always approach close packing for high volume fractions, i.e . c m = 0.74, and that the shear thinning is entirely due to the energy dissipation associated with hydrodynamic and colloidal particle interactions, which at low shear rates is larger than at high ones (for simple shear flows). The experimental data include those by Laun who measured the viscosity of concentrated latex dispersions over nine order of magnitude of shear rate ranging from 10 −3 to 10 6 s −1 , and Chu et al., who prepared several monodisperse latexes and measured the viscosity of individual as well as trimodal blends of these three latexes as a function of shear rate. The viscosity of carboxylated latex is also influenced by surface “hair”, which appears to be closely related to the amount and type of functional monomers, and degree of dissociation of carboxylic acid groups on the latex surface.