Model filled rubber. I: Effect of particle morphology on suspension rheology

Monodispersed polystyrene (PS) particels, crosslinked with divinylbenzene (DVB), were prepared by emulsifier‐free emulsion polymerization. The colloidal‐suspension rheology of a low‐molecular‐weight liquid polysulfide, which is used in commercial sealants, filled with these PS particles varying in size and particle‐crosslink density, was studied. At low frequencies or shear rates, the dynamic moduli and viscosity increased as particle diameter decreased from 1.25 to 0.315 μm or particle crosslink density increased from 0 to 5 mole% DVB. We suggest that particle‐particle interactions are dominant and lead to the formation of clusters in the concentrated suspension. Rheological properties associated with network buildup in suspensions were most sensitively monitored by a kinetic‐recovery experiment. The strength of, as well as the tendency for, cluster network formation in the colloidal suspensions increases with decreasing particle size, and increasing particle‐crosslink density, or decreasing surface roughness.