Rheometric properties of micron-sized CaCO3 suspensions stabilised by a physical polyol/silica gel for polyurethane foams
Résumé
This article considers the rheometric properties of mixtures containing a micron-sized mineral filler of calcium carbonate (CaCO3) in a polymer matrix gelled by adding colloidal silica (CS). These mixtures, consisting of a polymer matrix (polyols, catalysts, surfactant) are used to produce polyurethane foams. The suspending phase (polymer matrix/CS) has a yield stress that has been linked to fractal aggregation of the colloidal filler. Suspensions without any colloidal silica (polymer matrix/CaCO3), show aggregation of CaCO3 which is most probably due to the adsorption of catalysts present in the polymer matrix. Beyond a critical CaCO3 volume fraction, a yield stress is detected indicating a 3D connected structure. In the case of suspensions containing colloidal silica (polymer matrix/CaCO3/CS), the yield stress is due to a combination of the fracta network formed by the colloidal silica and aggregation of the micronsized particles of CaCO3.