Polymer dispersions and their interaction with mortar constituents and ceramic tile surfaces studied by zeta-potential measurements and atomic force microscopy

The interaction between mineral surfaces and organic polymer dispersions with different monomer base and protective colloids as present in tile adhesive mortar systems was investigated by measuring the ζ-potential and by direct observation by atomic force microscopy (AFM). The charge situation of pure mineral powders and pure polymer dispersions as well as their interaction in presence of different cementitious aqueous solutions was studied. The binding of Ca++ ions leads to positive ζ-potentials for quartz or ceramic in calcium containing aqueous solutions and acts as a transmitter of attractive forces. However, the adsorption of sulfate ions may disturb such attraction. The interaction between polymer dispersions and ceramic (polished and original tile) or mica surfaces influenced by the presence of artificial cementitious pore solutions was observed by AFM. A flat index (height/diameter of latex particles in contact with these surfaces) was defined to quantify the polymer–mineral interface affinity. The different flat indices for different polymer–substrate combinations are mainly related to two parameters, the glass transition temperature of the copolymer and the stabilization system (steric versus cationic). Furthermore tapping phase imaging revealed significant heterogeneities in the inner structure of the polymer particles and inhomogeneous distribution at their surface probably related to local variations of the protective colloid, especially polyvinyl alcohol.