Network Formation in Various Dispersing Medium of Hydrophobic Colloidal Silicon Dioxide
Colloidal silicon dioxide is a fine amorphous powder consisting of particles about 7-40 nm in size. This study utilized hydrophobic colloidal silicon dioxide, aerosil R 972, as gelling agent in non-aqueous systems. Aerosil R 972 could convert light mineral oil and Luvitol EHO® into gel at concentrations of 7 and 10% by weight, respectively. The appearance of the systems prepared from polyethylene glycol 400, 600 and light mineral oil was clear, but the others were turbid. There was no phase separation or color changes of the systems after temperature change of 6 cycles. The obtained gel exhibited very little change of pH and viscosity after stability testing. After aerosil R 972 was incorporated into the mixed media with different dielectric constant, all systems showed the decrease of a viscosity, especially, the formulations having low dielectric constant. The addition of aerosil R 972 into dispersing medium with higher dielectric constant provided higher viscosity of the system because of the mismatch of the polarity between particles and dispersing media. In case of the incorporation of aerosil R 972 into mixed media, the rank order of viscosity was PEG 400–glycerin> PEG 400–PG > PEG 400–water. All of PEG 400–glycerin mixtures were obviously converted into gel, while only PEG was not converted with aerosil R 972 addition.
P. Toprasri and T. Phaechamud, "Network Formation in Various Dispersing Medium of Hydrophobic Colloidal Silicon Dioxide", Applied Mechanics and Materials, Vols. 229-231, pp. 188-191, 2012