Structure and surface coverage of water-based stearate coatings on calcium carbonate nanoparticles

In a preceding paper, it was found that, during coating with solutions of a stearin salt in water, whatever the concentration used, a considerable part of the PCC surface remains free, indicating the development of an incomplete monolayer. This was explained by assuming a micelle adsorption mechanism as the dominating process in water, resulting in a multilayer structure composed of an inner incomplete chemisorbed monolayer and one or more physically adsorbed layers. This model predicted a physisorbed layer in which polar groups are oriented outwards of the particles, resulting in a hydrophilic surface, contrary to experimental evidence. In this paper, we propose that during the drying stage, the physisorbed calcium stearate layers undergo a complex rearrangement leading to a hydrophobic coating with the aliphatic tails oriented outwards of the particles. The results of XRD measurements proved that the physisorbed stearate layer is crystalline, while DSC model experiments indicated that the layer goes through phase transitions during heat treatment. The proposed model matched with IGC measurements, showing a clear dependence of the specific component of surface energy on the amount of absorbed stearin. The agreement with values obtained for solvent and dry-coated particles supports the proposed rearrangement of alkanoate molecules in the coating. This stearate is perfect for applications dosed by pneumatic transport systems. The dust-free product prevents the stearate from ending up in the system’s filters and remains in the chippings, pellets, ingredients, etc. Another advantage is that more accurate dosages and more efficient use of the product can be obtained. In addition to the material obtained by tumbling Big Bags by hand or in open spaces, this is much cleaner as it contains no dust. If you are looking for high quality, high purity, and cost-effective Water-based calcium stearate, or if you require the latest price of Water-based calcium stearate, please feel free to email contact mis-asia.

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