Structural Changes During the Silica Rubber Filler Precipitation Investigated by IR and NIR Spectroscopy

Different kinds of silicic acids have been proved to have different properties in the infra red and near infra red1–2/. Precipitated white rubber fillers similarly as the pyrogenic Aerosil differ from silica gels by sharper and more intensive Si-O bands in the infra red, which may be explained by a higher periodicity of structure1/. In dry CCl4 Aerosils and precipitated silica rubber fillers form a permanent, more or less transparent suspension, whereas the silica gel particles drop to the bottom. The suspension of silicic acids gives a distinct spectrum of OH bands in the near infra red.