(217bw) Characterization of Monomer Miniemulsion Stability

Miniemulsion polymerization is a new challenge on the universe of polymerization. Since last 10 years, it has been extensively studied due to its advantages when compared with conventional emulsion polymerization like the possibility incorporate inorganic solid compounds on the polymer particle resulting on nanocapsules.

In this study, we present two experiments data focused on the monomer miniemulsion preparation that is done before the polymerization reaction using dispersion devices. The most common and available equipment for emulsification are rotor-stator systems, sonifiers and high-pressure homogenizers. The miniemulsion preparation is as important as the miniemulsion chemical composition because it affects directly the monomer particle size and the miniemulsion stability obtained by the dispersion stage. This stage is determinant for the miniemulsion stability and too to the quality of the final polymer produced.

The miniemulsion preparation was made using rotor-stator system, T25 Ultra Turrax equipped with de S25N-25G disperser element with stirring from 3000 rpm to 25000 rpm. This equipment is based on the high shear to break the droplets by the turbulence produced on the vessel.

The miniemulsion stability was analyzed using two equipment: Coulter N4 Plus and Turbiscan. The first one was used to measure the particle size by dynamic light scattering on a diluted sample and the second one was used to measure the transmitted and scattered light by incident light on the concentrated sample and making the scanning and measure of the intensity light from the sample top to the bottom. This analyze is taken along the time and so it permits to make the qualitative and quantitative stability analyze. The Coulter is able to determine particles sizes from 3 nm to 3000 nm which is adequated to the mean particle size obtained after the monomer miniemulsion dispersion.

The experiments were planned using the design of experiments (DOE) methodology. This study analyzes two levels, two factors and two replicates of the central point. The six recipes were prepared with the same composition. The result of this study guaranty and choose the best formulation and procedure to produce a stable monomer miniemulsion which will be used on the next process where  the polymerization takes place. The result is in accordance with the reported by Asua, J. M, 2003 and shows that when we used high stirring velocity, during a high period of time we obtain a more stable monomer miniemulsion.