Rheology of polystyrene latexes with adsorbed and free gelatin |
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| Institution: | 1. Kodak European R&D, W93-GA, Harrow, Middlesex HA1 4TY, UK;2. Imaging Research & Advanced Development, Eastman Kodak Company, Rochester, NY 14650-2109, USA;1. Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe 610-0321, Japan;2. Faculty of Pharmaceutical Sciences, Suzuka University of Medical Science, Suzuka 513-8670, Japan;1. Department of Pharmaceutics, Institute of Pharmacy, University of Bonn, Germany;2. Zentrum für Ingenieurwissenschaften, Martin-Luther-Universität Halle-Wittenberg, Halle (Saale), Germany;1. Department of Physics, College of Education, Tikrit University, Tikrit, Iraq;2. School of Physics, Universiti Sains Malaysia, 11800 Penang, Malaysia;3. Al-Balqa Applied University, Ajloun University College, Jordan;4. Energy Materials Laboratory (EML), Physics Department, School of Sciences and Engineering, The American University in Cairo, New Cairo 11835, Egypt;1. Key Laboratory of Biorheological Science and Technology, Ministry of Education, College of Bioengineering, Chongqing University, Chongqing 400044, PR China;2. College of Chemical Engineering and Chemistry, Chongqing University of Science & Technology, Chongqing 401331, PR China |
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| Abstract: | The rheology of monodisperse polystyrene latex particles of two different particle radii (26 and 67 nm) has been studied with a range of concentrations of the polyampholyte gelatin. Gelatin contributes to the rheology by adsorption to the particles and by thickening the continuous phase. High viscosities and strong shear thinning are measured for low volume fractions of latex. A procedure is presented to deconvolute the effects of free and bound gelatin by applying simple hard-sphere models. This procedure allows us to estimate the effective size of the gelatin-covered particles as well as the continuous-phase gelatin concentration and viscosity. The layer thicknesses from rheology agree well with those from PCS. The effect of varying particle volume fraction, ionic strength, pH and gelatin and surfactant concentration on the rheology of these suspensions is presented. For the smaller latex, the adsorbed layer occupies a greater fraction of the effective volume. Increasing free polymer concentration reduces the adsorbed-layer thickness. The reduced critical shear stress increases with the suspension viscosity for suspensions of the 26 nm latex but is constant for the 67 nm latex. At very high shear (>2000 s−1), the suspensions show excess shear thinning over that expected from a hard-sphere model. This excess thinning is attributed to deformation of the adsorbed gelatin layer under high shear stress and interpreted in terms of an empirical interparticle potential. |
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