Fumed silica Functional coatings

INFRARED AND RAMAN SPECTROSCOPY ° ° 21-138 Applications The following use was made of infrared and Raman spectroscopy identification of surface groups on treated and untreated fumed silica, tion of silica functional groups and coatings by Raman spectroscopy. 

Hydrophobic Silicas. Because foaming is a surface phenomenon, any antifoam used must concentrate at the surface (or gas—liquid interface). Hydrophobic silicas, which are silicas that have been treated with a compound that causes them to float on the top of water, have been used to fulfill this function for almost 30 years. U.S. Patent 3 408 306 (5) discloses the use of a hydrophobic silica dispersed in a hydrocarbon oil. Hydrophobic silica for this composition, which is still in use today, is made either by continuous ( dry roast ) or batch process. In either process, precipitated silicas rather than silica gels or fumed silicas are typically used to make antifoams. During a continuous process, silicone oils, usually poly(dimethylsiloxane), are sprayed onto a bed of hydrophilic silica. The bed is heated to temperatures ranging up to 300 °C, and reaction times are up to 20 h. At these temperatures and reaction times, bond formation between the silica particle and silicone oil may occur in addition to simple coating of the particle. 

Applications The following use was made of infrared and Raman specfroseopy identification of surface groups on treated and untreated fumed silica, identification of silica functional groups and coatings by Raman spectroscopy, silane deposition on various fillers, surface grafting of barium sulfate by acryloamide grafting of wood fiber, specbal absorption of filler,crystallization of polymer in the presence of filler, absorption of polyacrylate on alumina, deformation of fibers in composites by Raman... 

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