This paper investigates the modeling of styrene free radical polymerization in two different types of micro-mixer for which the wall temperature is kept constant. The simulations are performed with the help of the finite elements method which allows solving simultaneously partial differential equations resulting from the hydrodynamics, thermal and mass transfer (convection, diffusion and chemical reaction). The different micro-mixers modeled are on one hand an interdigital multilamination micro-mixer with a large focusing section and on the other hand a simple T-junction with three different radii followed by a tube reactor having the same radius. The results are expressed in terms of reactor temperature, polydispersity index, number-average degree of polymerization and monomer conversion for different values of the chemical species diffusion coefficient. Despite of the heat released by the polymerization reaction, it was found that the thermal transfer in such microfluidic devices is high enough to ensure isothermal conditions. Concerning the polydispersity index, the range of diffusion coefficients over which the polydispersity index can be maintained close to the theoretical value for ideal conditions increases as the tube reactor radius decreases. The interdigital multilamination micro-mixer was found to act as a T-junction and tube reactor of 0,72 mm ID but gives up to 15% higher monomer conversion. This underlines that the use of microfluidic devices can lead to a better control of the polymerization.

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