Processing technical ceramics with maltodextrins: Crosslinking by acetalation
1999
Schilling, C.H. | Tomasik, P. | Cheol Kim, J.
Technical ceramics are made by a sequential process of: (i) mixing ceramic powder with an organic carrier liquid (e.g., organic solvents, polyethylene wax) to form a plastic slurry, (ii) molding the plastic slurry into a three-dimensional shape, (iii) thermal treatment to evaporate or pyrolyze the organic carrier, and (iv) kiln firing. In this paper, the use of aqueous polysaccharide solutions is examined as environmentally-friendly, economically-viable substitutes for organic carrier liquids in ceramic molding. The central focus of the present study is to examine optimum conditions for crosslinking model slurries of maltodextrin and colloidal aluminum oxide by acetalation of maltodextrin. Crosslinking is needed to prevent the common problem of cracks that form in ceramic shapes during thermal treatment (stage iii above). Experiments involving rheology and differential thermal analysis revealed that glyoxal and glutaraldehyde are effective crosslinkers, whereas formaldehyde and pyruvic acid did not exhibit measureable changes in slurry rheology over a wide range of concentrations. Glutaraldehyde reacted faster than glyoxal, however, glyoxal produced the strongest gels. Basic conditions catalyzed acetalation. The sequence of blending the slurry components had no significant effect on slurry rheology.
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