COLLOIDAL STABILIZATION OF BATIO3 WITH POLY(VINYL ALCOHOL) IN WATER

Several poly(vinyl alcohol) (PVA) based copolymers have been tested wi th respect to their ability to provide sterically stabilized BaTiO3 di spersions. Regular PVA types, regardless of the degree of hydrolysis a nd the vinyl acetate block character, cannot stabilize BaTiO3. Block c opolymers of PVA with a carboxylic acid-containing block proved to be successful. Random copolymers based on PVA with a few per cent of carb oxylic acid-containing monomers have also been studied. Some of these products can stabilize BaTiO3 while others cannot. Depletion flocculat ion is not found with the block copolymers but does occur with dispers ions stabilized with a random copolymer. The stabilizing mechanism is purely steric in the case of the block copolymers, and a combination o f steric and electrostatic repulsion with the stabilizing random copol ymer.