Highly open porous polymer foams were prepared via the polymerization of 10 : 1 styrene/divinylbenzene high-internal-phase emulsions (HIPEs) prepared under various emulsifying conditions. The effects of the emulsification stirring speed (SS) and rate of aqueous droplet-phase addition on the HIPE equilibrium torque value, an approximate characterization of HIVE viscosity, and the microstructure and properties of the resulting HIPE polymer solid foams were investigated. SS was varied over the range 400-1200 rpm for aqueous-droplet-phase addition rates (AARs) of 0.53 and 1.3 mL/min. The microscopic results showed that at lower AARs, increasing SS decreased the weighted-average cell diameter from 24.31 to 13.55 mu m, whereas the cell size distribution was broadened, and the intercellular pore size varied irregularly in the range 0.76-1.42 mu m. The average cell diameter and intercellular pore size for the solid foams prepared at higher AARs were greater than that of those prepared at lower AARs. The density of the foam materials ranged from 0.057 to 0.072 g/cm(3), whereas their thermal conductivity varied from 0.649 to 0.705 W m(-1) degrees C-1. The highest compressive stress-strain properties were found for the foam sample prepared with highest SS and a lower AAR. Adding electrolyte CaCl2 to HIPE produced remarkable increases in the void diameter and intercellular pore size, especially at lower SS values. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 116: 986-994, 2010