Analysis and optimization of viscosity of concentrated silica suspensions by response surface methodology (RSM): Control of particle modality

Rheology of dense polymer suspensions is of common importance, especially in the ceramics, composites, energetics, drilling fluids, magnetic and pharmaceutical researches. In the present work, the viscosity of concentrated suspensions of polydimethylsiloxane (PDMS) as fluid matrix and silica particles as the dispersed solid phase was modeled by response surface methodology (RSM). The effect of volume fraction of the particles (u) and modality parameters such as large-to-small particle size (.) and weight (d) ratio on the zero shear viscosity of suspensions (mu 0) was studied, and a good agreement between the model and experimental data was observed. The results of mathematical modeling showed that the minimum mu 0 was obtained at the highest value of u (0.768), when d and. were equal to 2.75 and 20, respectively. Moreover, the viscosity of the samples with a composition minimized by a theoretical model proposed by Yu and Standish was compared with that of obtained using RSM. At the same solid loading (74.15 vol%), the RSM-optimized zero shear viscosity (similar to 15000 Pa. s) was much lower than that obtained from Yu and Standish method (similar to 32000 Pa. s), which confirms the ability of RSM to optimize the viscosity of highly filled dispersion systems. [GRAPHICS] .