An investigation of droplet size and size distribution in methylmethacrylate suspensions in a batch oscillatory-baffled reactor

We report, for the first time, our experimental investigation of droplet size and size distribution in methylmethacrylate suspensions in a batch oscillatory-baffled reactor (OBR). Two recipes of different amounts of monomer were used in the tests, and samples containing monomer droplets in an aqueous phase were obtained and the images of the droplets were captured and analysed. We tested the uniformity of droplets along the reactor and identified a minimum oscillation time of 30 min, over which stable droplets are formed. We also examined the effect of oscillation amplitude and frequency, baffle thickness and the levels of surfactants on droplet size and size distribution in the OBR. Our experimental results show that the oscillation amplitude has displayed a similar effect as the oscillation frequency in controlling the droplet size and size distribution, and an increase in either decreased the droplet size and narrowed the distribution. The effect of the baffle thickness was unexpected, though generally small, and the trend was that the thicker baffle gave smaller droplet sizes and narrower distributions. The levels of surfactants have shown a significant effect on the droplet size and distribution. When a high concentration of surfactants was used, both the droplet size and size distribution greatly decreased. In this paper, we also discuss the mechanism of droplet formation and report a correlation established between the mean droplet size, d₃₂, and the oscillation velocity as d₃₂ = 0.996 × 10^-6 · (x₀f)^-1.2 and compare it with the conventional devices.