Fumed silica is one of the many modern super-substances. It’s a versatile chemical designed in the twentieth century and developed for applications across many industries.
In this article, we’ll take a closer look at this dynamic, useful chemical: when it was first used, how it’s manufactured, and what makes it unique. At the end of the article, ChemCeed also provides a list of common practical uses for fumed silica.
A Brief History of Fumed Silica
As far back as the Roman Empire, silica has been an important chemical in industry. The Romans– and nearly all societies since them– used silica to make concrete and glass. While silica is plentiful in nature, the artificial synthesis of fumed silica is relatively new. This particularly fine-particle iteration of silica was first synthesized by German chemist Harry Kloepfer in 1942.
This new fumed form of silica proved to be even more versatile in its applications than silica itself. In the 80 years since Kloepfer’s breakthrough, fumed silica has been synthesized and marketed in every nation in the world, across countless industries.
How Fumed Silica is Made
Chemists synthesize fumed silica via pyrolysis, the use of high temperature flame to break down matter. In this process, flame is applied to an easily vaporizable substance containing silica, such as silicon tetrachloride (a silica-heavy liquid), quartz sand, or coal.
This causes the silica to vaporize into the air. From there, the oxygen in the chamber condenses onto the vaporized silica particles. After the flame has cooled, the resulting oxidized silica particles are gathered and sold as fumed silica.
What makes fumed silica unique?
Fumed silica has a number of unique properties that make it useful in a wide variety of industries. Let’s look at some of the most important–and appealing–properties of this remarkable substance.
Fumed silica is…
- Hydrophilic. In other words, it absorbs moisture readily. (Unless it’s specially treated to be hydrophobic, or moisture resistant.)
- Thixotropic when wet. In other words, once fumed absorbs moisture, it is viscous and relatively free-flowing, but thickens quickly under pressure. Moisturized fumed silica also thickens simply by drying out.
- Bulky but fluffy. In other words, fumed silica particles have a high surface area, relative to their mass. Fumed silica particles are, in a sense, similar to tiny cotton balls: lightweight, but with a surface area that allows them to fill up a lot of space.
- High purity: Fumed silica is silica and oxygen… and nothing else, unless artificially treated or manipulated. This makes its behavior very predictable, both in laboratory and manufacturing contexts.
What is the difference between fumed silica, precipitated silica, and silica gel?
Silica gel and precipitated silica are similar to fumed silica, yet distinctly different from it. Below is a brief explanation of the differences between fumed silica and two other commonly used industrial silica substances.
Fumed silica vs. precipitated silica
- Precipitated silica is a microparticle, while fumed silica is a much smaller nanoparticle.
- Precipitated silica is less pure than fumed silica. (Precipitated silica has ~93% purity, compared to fumed silica’s greater-than-99% purity.)
Fumed silica vs. silica gel
- Silica gel is liquid, while fumed silica is dry but hydrophilic.
- Silica gel particles are bonded together in a lattice network, while fumed silica is a fine nanopowder made of easily separable individual nanoparticles.
- In spite of these differences, it’s worth noting that both fumed silica and silica gel are very high purity.
Common Uses of Fumed Silica
- Paints, adhesives, and other fluids that need to dry and set:
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- Because it’s hydrophilic yet thixotropic (as discussed earlier in the list of unique properties), fumed silica helps paints and adhesives both flow and thicken/bond as they need to.
- Concrete, rubber, plastic, and other materials that need to be reinforced and strengthened
- Fumed silica’s ability to bond under pressure, as well as its fine nanoparticle size, make it a very effective additive to solid parts in machinery and construction.
- Food production and packaging.
- Here is another instance where fumed silica’s hydrophilic nature comes in handy. Fumed silica is placed in dry food packaging or added to powdered foods to reduce moisture and prevent caking. Fumed silica accomplishes that by readily drawing moisture into itself and away from the food.
- Fumed silica’s absorptive nature also allows it to thicken wet foods/beverages, such as milkshakes.
- In agriculture, this chemical also helps keep seeds dry, and prevents fertilizer and other powdery agricultural supplies from caking.
- Health, beauty, and personal care:
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- The light but not transparent color of fumed silica, combined with its nano-sized fine texture make this chemical useful in diffusing light. As a result, it’s used in sunblock and other cosmetic products designed to shelter skin from the sun.
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- The fine nanoparticles of fumed silica also serve as a mild abrasive, making it a common additive in toothpaste.
- Material fabrication
- The mild but very fine abrasive properties of fumed silica also make it an excellent polishing and smoothing agent for metals and other materials, so that parts in machines and electronic devices can be made smooth.
For more information on the fumed silica offered by ChemCeed, please visit our Fumed Silica Product Page