Surface-modified silicas prepared pyrogenically

Surface-modified, pyrogenically prepared silica is prepared by subjecting the pyrogenically prepared silica, which is in the form of aggregates of primary particles having a BET surface area of 300±25 m2/g and the aggregates have an average area of 4800-6000 nm2, an average equivalent circle diameter (ECD) of 60-80 nm and an average circumference of 580-750 nm, to surface-modification in a known way. It can be used as a filler for controlling the rheology of liquid silicone rubber (LSR) systems.