Smectite

A highly plastic clay mineral related to montmorillonite (bentonite), more correctly, the name of the group on minerals that includes montmorillonite and other similar minerals. CAS# 1327-43-1 is magnesium aluminosilicate, a family of minerals. CAS# 12199-37-0 is smectite, a specific kind of magnesium aluminosilicate.

The following was obtained from Southern Clay Minerals:
Smectite is a platy clay mineral. Three properties make smectite unique:

Shape - Smectite is a very lamellar material. Individual platelets resemble a business card in terms of morphology.

Size - Naturally occurring smectite ranges in size from 0.25 microns up to 0.75 microns across its broadest dimension.

Charge - Smectite platelets have a negative ionic charge within the body of the platelet and a positive charge on the edge of the platelet.

Due to its particular combination of properties, smectite can provide a host of benefits in water-based coatings. Due to its ability to structure in aqueous media, it is a thickener in low to mid shear ranges. Oftentimes it can be used to reduce or replace (in combination with other thickeners) cellulosic thickeners. It also prevents settling and syneresis (phase separation). Smectite will act as a pigment spacer (U.S. Patent 5,700,319) to improve hiding in titanium dioxide pigmented systems. Smectite improves sag resistance while not affecting flow and levelling to the extent other mineral thickeners might. This is due to smectite's true thixotropy which affords a delay in the recovery of viscosity when shear is released as opposed to the pseudoplastic tendencies of other minerals which cause an immediate recovery of viscosity.

Related Information

Links

Materials	B Clay
Materials	Laponite RD
Materials	Veegum A clay of incredibly small particle size. It has the highest plasticity of any known clay and acts as a suspending and gelling agent in slurries.
URLs	http://en.wikipedia.org/wiki/Smectite Smectite on WikiPedia
URLs	http://www.permont.com/ Southern Clay Products Smectite Minerals website
URLs	http://www.minersoc.org/pages/gallery/claypix/smectite/YM01.html One of many smectite micrographs at minersoc.org
Typecodes	Clay Minerals The property of plasticity is evident in a wide array of materials of different mineralogy. In addition, many minerals are considered parent minerals to clays, they weather down to become these clays.
Minerals	Montmorillonite, Bentonite A clay mineral of extremely small particle size and high plasticity. Raw bentonite is generally a pa
Minerals	Hectorite An uncommon fine grained highly plastic clay mineral related to bentonite. Named after Hector, CA. F
Glossary	Porcelain How do you make porcelain? There is a surprisingly simple logic to formulating them and to adjusting their working, drying, glazing and firing properties for different purposes.
Glossary	Clay What is clay? How is it different than dirt? For ceramics, the answer lies on the microscopic level with the particle shape, size and how the surfaces interact with water.

By Tony Hansen
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