Two-Stage Stabiliser Addition Protocol as a Means to Reduce the Size and Improve the Uniformity of Polymer Beads in Suspension Polymerisation

A 2-stage stabiliser addition protocol is suggested for reducing the size and improving the uniformity of polymer beads resulting from conventional suspension polymerisation. The stabiliser load was divided into an initial charge and a secondary addition. The use of a low concentration of stabilizer in the initial charge served to assist drop rupture while avoiding significant reduction in drop size and production of too many satellite droplets. The secondary addition time of stabiliser occurred just before the onset of the growth stage when drops were vulnerable to coalescence but were robust against break up due to their high viscosity. The secondary addition of stabiliser served to provide stability to monomer drops during the growth stage and as a result the drops underwent limited coalescence. This resulted in the formation of smaller and more uniform polymer beads in comparison to beads obtained by conventional suspension polymerisation at the same overall concentration of stabiliser.