Mecanismo físico-químico de aderência na interface argamassa modificada com polímeros/cerâmica de revestimento

Abstract

Ceramic tiles have been used for centuries for the exterior facades of buildings. The installation of tiles on exterior walls imparts both durability and aesthetic appeal to the facade and hence it has been a choice for buildings owners. However, failure of ceramic tile systems, with detachment of ceramic pieces from building facades, has caused a significant decrease of new buildings with tiled facades owing to the insufficient assurances provided by tiling performance. Also ceramictiles choice is being replaced by alternative materials and solutions which are capable of offering comparable visual appeal and equivalent functional performance. In this sense, the object of this work was evaluate the nature of interactions between ceramic tiles and polymer modified mortars in order to improve adhesion between tiles and polymer. The work was developed using EVA (poly(ethylene-co-vinyl acetate) and PVA (poly(vinyl alcohol)) as cement modifiers because redispersible powders based on EVA are the standard polymer base of the market. PVA is a water soluble polymer with the same chemical groups of interest and it is used as EVA emulsion stabilizer. This work includes materials characterization, evaluation of polymers stability in alkaline medium and polymers influence on fresh and hardenedmortar properties. Finally, adherence resistance measurements were carried out and a nano and micro approach of interface formation was identified. Based on chemical features of these polymers and ceramic tiles, only the weak van der Waals forces and hydrogen bonds may beexpected to be developed between tiles and polymer. Then the use organosilanes as primers was proposed in order to enhance better adhesion between tiles and mortar. Amino, mercapto, vinyl, methacrylic, and isocyanate groups were chosen as reactive groups of silanes for evaluating their compatibility with polymer and cement. In order to assess the effect on adhesion properties, unmodified and modified glass tiles were installed onto a cement based substrate using mortars with and without polymer (PVA and EVA) and pull-off tests were conducted. The adherence results were quite variable with some functional groups were able to improve adherence with unmodified mortars in more than 500%. The measured values reflected the overall balance of silane, cement and polymer features including reactive organofunctional group, organic spacer group, hydrophobic/hydrophilic features, kind of interactions developed between silane and polymer and silane and cement, including covalent bonds.