RHEOLOGY CONTROL OF ORGANIC COATINGS WITH NEW HYDROPHOBIC SILICAS

The rheological effects of hydrophobic pyrogenic silicas were examined using binder systems designed, in particular, for automobile top coat s. Rheological measurements to characterize the flow behaviour. especi ally with regard to sagging, in the relevant shear rate and shear stre ss were carried out in addition to practical tests. By means of a shea r strain jump experiment the rheological conditions during and directl y after paint application were simulated using a rheometer. Based on t he results obtained and additional measurement of viscoelastic paramet ers a new approach to understanding the mechanism of rheology control with pyrogenic silicas in coating systems was developed.