Sodium polyacrylate dispersants like Allied Colloids 311 and Darvan #7 are used as a superior alternative to sodium silicate. Advantages are:
-a lower minimum viscosity can be achieved and maintained longer
-faster casting rate at minimum viscosity
-flatter over-deflocculation curve
-higher green strength allowing removal from mold at higher water content
-.05 to .2% required which is less than sodium silicate
-best absorption and penetration into plaster
-little or no efflorescence on molds (build up of fuzzy salt deposits) because the sodium ion is tied up in the organic deflocculant and will not exchange places with the calcium ion in the plaster as with soda ash and sodium silicate.
-less silica remains in the pore structure of the plaster.
This material is also used as a binder in ceramic bodies.
Out Bound Links
An overview of the major types of organic and inorganic binders used in various different ceramic industries.