So you need an ingredient that can stabilize a water-in-oil emulsion, prevent caking, thicken oil, or perform myriad other roles in your formulation? You may want to take a look at fumed silica (EU: fumed silica). This useful ingredient technology is one that every formulator should have at the ready.
Fumed silica is made from flame pyrolysis of silicon tetrachloride or from quartz and is vaporized in a 3000°C electric arc. The particles are non-porous and have a surface area of 50–600 m2/g, primary particle size of 5–50 nm, and density of 160–190 kg/m3. It consists of amorphous silica fused into branched, chainlike, three-dimensional secondary particles, which then agglomerate into tertiary particles. The resulting powder has an extremely low bulk density and high surface area. Major global producers are Evonik (Aerosil), Cabot Corporation (Cab-O-Sil), Wacker Chemie (HDK), and OCI (Konasil). (EU: Evonik | Wacker Chemie)
- Can be used to convert a liquid to a powder, typical loading is 67% oil and 33% powder.
- Can create a powder containing up to 95% water using hydrophobic fumed silica.
- Flow aid to prevent caking.
- Thicken oil, clear if refractive index is matched.
- Increase the viscosity of water in oil emulsions.
- Stabilize water in oil emulsions.
- Form surfactant free Pickering emulsions.
- Increase the wash resistance and boost the SPF of sunscreen formulations (using hydrophobic fumed silica).
- Suspend and prevent agglomeration of powdered antiperspirant actives in sprays and roll-ons.
- Helps prevent skin whitening in A/P sprays vs. using clays as active suspending aids.
- Can be used as thickening and stabilizing agents in bleaching creams.
- A combination of fumed silica and quaternary ammonium compounds in hair rinses improves combability and volume of hair. (EU: quaternary ammonium compounds)
- Is an effective processing aid for grinding, screening or sieving powders.
- Improves the distribution of pigments and prevents settling in nail enamel formulations.
- Significantly improves lipstick payoff color uniformity, stability, and wear time. (see image above right)
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