Suspended Droplet Polymerization in an Unstable, Vibrating Shallow-Bed Reactor

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© 2016 American Chemical Society. A piston-driven shallow bed reactor (5.9 cm high) was used to conduct suspension polymerization under unstable flow conditions, which produced excellent mixing and droplet breakage. The instability started at the air/solution interface and carried through to the complete solution volume. The liquid interfacial instability described in the classic paper on this subject [T. B. Benjamin and F. Ursell, Proc. R. Soc. London A, Math. Phys. Sci. 1954, 225, 505-515] leads to a set of Mathieu equations, which map out regions of instability to guide the selection of amplitude and frequency. The current work operated exclusively in the half-frequency region of the instability curves. The performance was compared with a conventional impeller reactor. Both reactors operated in the power range of 0.3-20 W/kg. Only the piston reactor was capable of producing microparticles smaller than the Komolgorov scale, for the amine-initiated Michael addition of a trithiol to a triacrylate. The Hinze breakage model was used to correlate the mean particle sizes for impeller work. The pulsed-piston reactor particle size data required testing sub-Kolmogorov models to fit the mean particle size, and a viscous model [R. Shinnar, J. Fluid Mech. 1961, 10, 259-275] gave a good fit. Reactions conducted in the stable region of the Mathieu equation were highly ineffective.

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Industrial and Engineering Chemistry Research

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