The anticaking effect: Evonik silica improve storage stability for powders and prevent clumping
SIPERNAT® specialty silica and AEROSIL® fumed silica from Evonik prevent powders from clumping during storage and shipping, and ensure that they flow well. Known as the “anticaking” effect, this phenomenon is closely related to the “free-flow effect”, except that the free-flow effect is a function of flowability at a given moment, whereas the anticaking effect is related to long-term stability.
SIPERNAT® 22 S avoids formation of hard lumps in milk powder.
A food emulsifier without (left) and with (right) added SIPERNAT® 350.
The addition of SIPERNAT® allows animal feeds to flow freely.
A plastic granulate that has caked (right) and a plastic granulate to which SIPERNAT® 22 S has been added (left).
As described in the section entitled “Free-flow effect", the flowability of a powder is a critical factor in determining whether the material is easy to dispense and handle. In order to guarantee those characteristics—even after storing a product and shipping it to the customer—the ability to avoid caking over relatively long periods of time is crucial. Evonik meets this need with a wide-ranging portfolio of SIPERNAT® specialty silica and AEROSIL® fumed silica, which are extremely effective when added in even tiny amounts. These products significantly improve long-term stability, even in substances that readily form clumps, such as waxes or thermoplastic polymers.
Powders may form clumps due to deformation of malleable powder particles during storage, for instance, or, in the case of hygroscopic powders, because particles absorb and release moisture, triggering a recrystallization process. The anticaking effect is similar to that observed in flow enhancers: AEROSIL® or SIPERNAT® particles form an envelope surrounding the particles of the powder being treated—known as the “host” powder. This process prevents the powder particles from growing together. Achieving the long-lasting impact of the anticaking effect, however, requires somewhat higher amounts of additive than needed to bring about a free-flow effect alone.
SIPERNAT® and AEROSIL® products can be worked into the host powder through the use of appropriate mixing devices (such as a plowshare mixer, paddle mixer, or ribbon blender). For plastic powders or granulates that readily undergo deformation, it is especially important to ensure a gentle blending process so that the silica are not pressed into the surface of the powder particles.
SIPERNAT® and AEROSIL® products are used as anticaking agents in applications such as food and animal feeds, polymer granulates, laundry detergents, industrial chemicals, and much more.