Rheological Sensitivity Analysis of Polystyrene Latex Dispersed in Gelatin Solution

Abstract

The theoretical results produced by the Hone and Howe Phenomenological Model for the low shear viscosity of polystyrene latex-gelatin dispersions were compared to experimental data. Polystyrene latex particles were used as a model to analyse the rheological behaviour of the photographic (colour coupler) dispersions. The polystyrene latex particles analysed were 70 nm in diameter and were suspended in 10% (by weight) gelatin solution. An adsorbed gelatin layer of 28 nm was determined from previous work and was assumed for this study. As the temperature was increased, the accuracy of the rheological model also increased. A sensitivity analysis was performed (by varying the scaling factor) on the Hone and Howe Model across changing temperatures and latex volume fractions. A linear relationship was observed between the scaling factor and temperature for a constant latex volume fraction. However, a correlation between the scaling factor and the two latex volume fractions (8 and 5%) was not apparent. Further experimentation could be used to identify such a correlation. Rheological results for four latex particle diameters were also analysed (70, 380, 660 and 1094 nm). It was shown that at larger particles sizes (>100 nm) the scaling factor was independent of temperature. Furthermore, for larger latex particles, the hard sphere and Hone and Howe models produce results relatively close to one another. This was expected as such particle sizes can be treated as hard spheres with little compressibility of the gelatin layer. Lastly, the rheology of two colour coupler dispersions (supplied by Kodak Australasia Pty. Ltd.) was also analysed. Clear linear relationships were observed between temperature and scaling factor for these substances.