Fumed silica having a BET surface area of 200±15 m2/g, a grindometer value of less than 30 μm and a median value by PCS of 65 to 85 nm is prepared by grinding a fumed silica having a surface area of 200±25 m2/g, and silicone rubber containing this silica.
1. Hydrophilic milled fumed silica prepared by a process having no propensity to reagglomerate, comprising grinding fumed silica having a BET surface area of 200±25 m 2 /g and recovering a hydrophilic milled fumed silica that exhibits lower grindometer values and smaller median values than the starting fumed silica, wherein the hydrophilic milled fumed silica contains no hydrophobic fractions and has the following physicochemical data:
BET surface area
200 ± 15 m 2 /g
Grindometer value
less than 30 μm
Median value by PCS
65 to 85 nm
D50
12 to 14 weight distribution
Particle size span
5.260 to 34.70 nm
Particle size mean
11.5 to 13.5 nm.
2. A composition comprising silicone rubber and the hydrophilic milled fumed silica according to claim 1 .
3. Silicone rubber composition comprising 0.5% to 60% by weight of the hydrophilic milled fumed silica according to claim 1 .
4. The silicone rubber composition according to claim 3 which is vulcanized.
5. An article of manufacture made from the vulcanize silicone rubber composition of claim 4 .
6. The hydrophilic milled fumed silica according to claim 1 which has no particles in the range greater than 40 μm.