Sepiolite
Sepiolite is a non-swelling, lightweight, porous clay. Unlike other clays, the individual particles of Sepiolite have a needle-like shape, as shown in the picture below. The high surface area as expressed in M2/gm. and porosity, as well as the unusual particle shape of this clay accounts for outstanding colloidal properties and reinforcing characteristics. This valuable material is applied in a wide range of industrial applications.
Chemically, Sepiolite is a hydrated magnesium silicate. Its structure can be described as chain-like, producing needle-like particles instead of plate-like particles of other common clays. There is little negative charge on the crystal lattice resulting in low cation exchange capacity.
Colloidal grades of Sepiolite must be dispersed into water or other liquid systems using high-shear mixers. Once dispersed in the liquid, it forms a structure of randomly intermeshed elongated particles, which are maintained by physical interference and hydrogen bonding that entraps the liquid, thereby stabilizing the emulsion. This structure in Sepiolite is stable even in systems containing surfactants. On the other hand, bentonite clay suspensions will flocculate and fail when certain surfactants and/or ionic solutions are introduced.
Picture: Sepiolite "ribbons" shown at 50,000 times magnification using SEM (Scanning Electron Microscope). The long Sepiolite reinforcing ribbons are clearly visible. The Sepiolite is non-swelling and does not rehydrate when the applied sealcoat is exposed to moisture.