Hydrophobic Fumed Silica

Hydrophobic fumed silica refers to fumed silica nanoparticles that have been surface-treated to exhibit hydrophobic properties. Fumed silica, also known as pyrogenic silica, is a fine powder composed of amorphous silicon dioxide (SiO2) particles that are produced by burning silicon tetrachloride in a flame of hydrogen and oxygen. These nanoparticles have a very high surface area and are highly porous.

The hydrophobic modification of fumed silica involves treating the surface of the nanoparticles with various organic compounds or silanes to make them water-repellent. This modification alters the surface chemistry of the silica particles, reducing their affinity for water. As a result, hydrophobic fumed silica tends to form aggregates or agglomerates in aqueous solutions, rather than dispersing evenly.

Applications

Rheology control in paints and coatings: Hydrophobic fumed silica is used as a rheology modifier in paints, coatings, and adhesives to control viscosity, thixotropy, and sag resistance. It helps improve the flow and leveling properties of these materials while enhancing their water resistance.

Silicone rubber and elastomers: Hydrophobic fumed silica is incorporated into silicone rubber formulations to improve reinforcement, tear strength, and abrasion resistance. It also helps prevent moisture ingress into the rubber, extending its lifespan in various applications.

Printing inks and toners: Hydrophobic fumed silica is used in printing inks and toners to improve pigment dispersion, reduce viscosity, and enhance rub resistance. It helps maintain print quality and durability, especially in water-based inkjet inks.

Personal care products: Hydrophobic fumed silica is employed in cosmetics and personal care products such as creams, lotions, and hair care formulations as a thickening agent, suspending agent, or anti-caking agent. Its hydrophobic nature allows it to impart desired texture and stability to these products.

Powder coatings and composites: Hydrophobic fumed silica is added to powder coatings and composite materials to enhance flow, leveling, and mechanical properties. It helps reduce clumping and improves the dispersion of pigments and fillers in these materials.