Recent progress in the area of nanotechnology has already made it possible to commercialise of several products that contain nanoparticles and numerous others are under development. The manufacture of products that consist of nanoparticle suspensions requires the incorporation of nanoparticles in the liquid phase, break up of nanoparticle clusters and stabilisation. Often the process is carried out in several devices run in series to achieve the desired final product quality. In order for nanoparticles to be highly functional in the final product, it is critical that they are dispersed as close as possible to their primary particle size. In addition, the dispersion has to be stable, i.e. re-aggregation or re-agglomeration should not occur. In this study, which carried out as part of a large EC funded project, PROFORM, the break up of nanoparticle agglomerates is investigated using an in-line rotor-stator.

A custom built inline rotor-stator from Silverson, 150/250MS with inner General Purpose Disintegrating Head (GPDH) and Outer Square Hole High Shear Screen (SQHS), was used. The test medium used consisted of Aerosil® 200V manufactured by Degussa and distilled water. Aerosil® 200V is a densified hydrophilic fumed silica (> 99.8% SiO2 by weight) with an primary particle size of about 12 nm. It is used in several industrial applications: paints and coatings, unsaturated polyester resins, laminated resins, and gel coaters, adhesives and sealants, printing inks as an anti-settling, and anti-sagging agent, or rheology modifier.

Experiments were run to investigate the effect of process conditions and the rotor speed was varied in the range of 3000 to 9000 rpm and flow rate in the range of 0.3 to 1.5 l s-1. Particle concentrations of 1, 5, 15 and 20 % by weight were studied.

The presentation will focus on the analysis of data obtained in terms of particle size distributions and mean diameters and will elaborate on the way in which coarse and fine (micron and sub-micron) particles are generated over a period of time. The effect of energy input and changing solids concentration will be shown. Some model predictions will also be included. These results are also used to validate the CFD simulations (Baldyga et al), which are presented in another session (06005).