Macromolecular Thickeners and Binders

In this section properties of macromolecular thickeners and binders are discussed. Usually, binder polymers also have thickening properties and in ceramics both functions are often denoted by the term binder [21]. 

Reasons for the presence of macromolecular additives in coating suspension formulations can be  

It is beyond the scope of this chapter to give a full account of these reasons. Only the most important aspects will be highlighted. The discussion is further limited to the aqueous systems as usually used in the dip-coating of support coatings. The interested reader is referred to Refs. [28,75-80] for more information. 

Ringenbach et al. [81] investigated the adsorption mechanism of polycar-boxylic acid on alumina. The complex formation between polyanion and dissolved aluminium cations appears to play an important role in determining the properties of the adsorbed layer. This may explain the decrease in stability of polyelectrolyte suspensions with time. 

In the presence of a binder polymer such as PVA the electrostatic repulsion between the particles decreases to some extent [12]. However, no effect of PVA on the wet packing density was observed at maximum polyelectrolyte adsorption. On the contrary de Laat and Berks [82] observed that polyelectrolyte stabilised BaTiOs suspensions flocculated upon addition of PVA. 

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