Rheology of synthetic latex. II. Concentration dependence of flow in type V GR-S latex

• Published in: Journal of colloid science 1951, Vol.6 (6), p.584-591
• Main Authors: Maron, S.H., Madow, B.P., Krieger, I.M.
• Format: Article
• Language: English
• ISSN: 0095-8522
• DOI: 10.1016/0095-8522(51)90057-8

Type V GR-S latex is non-Newtonian at all concentrations above about 0.25 rubber by volume, Newtonian below. The exponential flow equation may be used to convert experimental observations in capillary and concentric cylinder viscometers to rate of shear and shearing stress values. For volume fractions above about 0.40, however, separate exponential equations must be used for the high and low shearing stress ranges, due to the inadequacy of a single two-parameter equation to express the wide variation observed. The constants N and η′ of the exponential equation increase in a regular manner with concentration for both shearing stress ranges up to a volume fraction of about 0.60, and either decrease or “level off” from 0.60 to 0.62, the highest concentration studied. This unusual behavior, equivalent to a decrease in viscosity with increasing volume fraction, is tentatively attributed to the setting in of a degree of order, which would restrict Brownian motion of the particles, and permit flow to occur along more or less definite planes. An empirical extension of the Einstein equation of the form log η′ η 0 = bZ, where Z = αφ 1 − αφ , holds well all the way from 0 to 0.60 volume fraction of rubber. The limiting form of this equation at low volume fraction is identical with that of the Einstein equation, with a factor not far from Einstein value of 2.5. Extrapolation of the formula predicts infinite viscosity at a total volume fraction of rubber plus an adsorbed soap monolayer of about 0.75-0.77, a value which corresponds closely to the maximum obtainable by tight packing of spheres.