Effects of Hydrophobic Silica on the Performance of Silicone-Based Antifoams

The efficiency of an antifoam consists of polydimethylsiloxane oil, hydrophobe silica particles, and either Sodium Dodecyl Sulfate (SDS) as an anionic surfactant, or Octyl phenyl deca ethylene oxide (Triton X-100) as nonionic surfactant for use in aqueous system is investigated. The performance of different combinations of oil, silica particles, and surfactant in control of foam height was determined using Bickerman Shaking test. The effect of surfactant in reducing the surface tension was determined using Wilhelmy test. The sizes of dispersed oil droplets and silica particles were determined using both optical and electronic microscopy. It was found that increasing the silica content of the antifoam mixture and using sharp-edged particles increase the performance of antifoam and decrease the foam disappearance time. This Observation was the same for both cases of using anionic and nonionic surfactants. It was also found that, as the inert gas purging rate increases, the time of deactivation decreases to less than a minute; a favorable performance for good quality antifoam.