The influence of stabilizing agents on the interaction between styrene/butadiene latex and calcium carbonate: a calorimetric and a dynamic electrokinetic study

The role of stabilizing agents in the interaction between styrene/butadiene latex and calcium carbonate particles has been studied using isothermal titration calorimetry (ITC) and an electrokinetic sonic amplitude (ESA) technique. It is demonstrated that the polyacrylate sodium salt (dispersing agent, referred to as NaPA) used as stabilizing agent for the calcium carbonate suspensions principally affects the interfacial properties of the calcite surface. An electrostatic barrier is created and this decreases the attractive interactions between the latex and the negatively charged mineral surface. The total enthalpy change observed when an emulsion of styrene/butadiene particles substantially free from surfactant was added to the dispersed calcium carbonate could be described via a relatively complex path. The process included (i) an exothermic response from the association of the latex particles (adsorption process) with the dispersed calcium carbonate surface and (ii) an endothermic bulk phase effect due to the adsorption on the latex particles of dissolved species originating from the calcium carbonate. Stabilization of the latex particles with sodium dodecyl benzene sulfonate (SDBS) or a non-ionic fatty alcohol ethoxylate surfactant did not significantly change the enthalpy of interaction. It was further demonstrated that SDBS had a very weak affinity for the dispersed calcium carbonate particles and that dissolution of species, such as calcium ions, from the calcium carbonate surface, allows further adsorption of SDBS onto the latex particles.