Polymeric flocculation of ceramic slurry obtained by the Direct Coagulation Casting

Katarzyna Jach ,  Mikołaj Szafran 

Warsaw University of Technology, Faculty of Chemistry, Noakowskiego 3, Warszawa 00-664, Poland

Abstract

The role of enzymes in Direct Coagulation Casting forming method consists in the decomposition of an appropriately selected substance, which results in slow release over the whole volume of a substance changing the pH of the system modifying the double electric layer. In the case of applying a powder of a suitable composition, profiles of high density and relatively high mechanical strength in the green state enabling the removal of a green product from the form without destruction can be obtained by this method.
The assurance of a respective mechanical strength of a green samples is a technological problem when forming products of a complicated shape. This requires the introduction of a certain amount of a polymeric binder, often of high molecular weight. Such binders cause a considerable increase in the viscosity of ceramic casting slips, which in turn precludes the exact filling of the form.
This problem can be partly minimized by introducing a binder simultaneously playing the role of a flocculant of the ceramic casting slip. If the flocculation is carried out with the participation of enzymes, then at a relatively small rate of such a reaction appropriate fitting of the ceramic powder particles is possible, which should lead to an improvement in the uniformity of thickening in the ceramic product formed.
The slow decomposition of a respective starting material by an enzyme should cause a change in the character of interactions between particular bundles of the polymer chains and change their conformation to a dense net of entanglements. This should result also in the transfer of the ceramic casting slip from the state of small viscosity to that of a stiff material, additionally strengthened by a bond between the individual particles of the ceramic powder and the binder.

Presentation: poster at E-MRS Fall Meeting 2003, Symposium B, by Katarzyna Jach
See On-line Journal of E-MRS Fall Meeting 2003

Submitted: 2003-05-27 18:00
Revised:   2009-06-08 12:55
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