The Role of Polymer Compatibility in Ceramic Processing
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Abstract
The proper use of multiple polymeric additives in ceramic processing is discussed. First, the use of a polyelectrolyte as a dispersant is studied by looking at the adsorption of various molecular weight PAAs on clay and the effect on suspension rheology. The adsorption of PAA on clay particles is not influenced by molecular weight, but there exists an optimal chain length for minimum viscosity. Secondly, the interactions between polymeric additives in suspensions and during drying are investigated. The phase behavior of polymer systems is studied by Flory-Huggins theory and the interactions in polymer solutions are examined using light scattering and optical microscopy. The results are used to explain the PVA migration behavior. PVA can be stained and its location within the spray dried granule can be observed, verifying the effect of other polymers on binder migration. It is shown that phase separation of polymer systems is the primary reason for the PVA migration. The chain length and functional groups of polymers determine the phase behavior of polymers and in turn the degree of binder migration.