Published online by Cambridge University Press: 01 January 2024
The viscosimetric constants of aqueous suspensions of certain homoionic forms of mont-morillonite and attapulgite were measured following adsorption of different kinds and quantities of organic polymers. Dissymmetry and interaction of the clay—organic complexes were then calculated from the Schulz-Blaschke equation and their structures deduced.
A positive, linear relationship was found between the dissymmetry of H- and Al-montmorillonite, respectively, and the amount of vinyl acetate maleic anhydride (VAMA) adsorbed-H-montmorillonite displayed the greater dissymmetry and it is inferred that H-montmoril. lonite complexes consist of an edge-to-edge linkage of clay particles through lattice-aluminumcarboxyl bonds. Al-montmorillonite permits three kinds of linkage: edge-to-edge (as with H-montmorillonite), external flat surface-to-surface (producing a “stacked” structure), and surface-to-edge, the last two involving exchangeable aluminum-carboxyl bonds. Edge-to-edge linkages probably predominate.
Ca-montmorillonite is unaffected by less than 8 parts of VAMA per thousand of clay. Edge-to-edge linked clay particles appear at this ratio and interaction diminishes. Delayed structural organization can be explained by low polymer adsorption at high initial pH. Maximum dissymmetry of H-montmorillonite-VAMA complexes occurred after titration with NaOH to pH between 6 and 8, above which mutual repulsion between highly dissociated polymer and clay may restrict linkage.
H-attapulgite—VAMA complexes are dissymmetrical for low VAMA adsorption but increased adsorption reduces dissymmetry and bundles of edge-to-edge linked particles are formed.
Probable structures of montmorillonite complexes with other polymers are also discussed.