Polymer/calcium carbonate CaCO

Of the various mineral fillers used, calcium carbonate (CaCO ) is one of the most common, due mainly to its availability in readily usable form and low cost [76]. However, the incompatibility of its high energetic hydrophilic surface with the low-energy surface of hydrophobic polymers, e.g., polyethylene (PE) and polypropylene (PP), is a particular problem. For this and other reasons, the surface of calcite is often rendered organophilic by a variety of surface modifiers such as silanes, titanates, phosphates, and stearic acid. 

Zhou and co-workers [27] studied the effect of surface treatment of calcium carbonate with sulfonated PEEK on the mechanical properties of the polymer. Tests used included tensile tests, flexural tests, notched Izod impact tests, TGA, DSC and SEM. The modulus and yield stress of the composites increased with CaCOs particle loading. This increase was attributed to the bonding between the particles and the PEEK matrix, was proved by the SEM of the tensile fracture surface of the composites. The treated fillers were found to give a better combination of properties, which indicated that the sulfonated PEEK played a constructive role in the calcium carbonate/PEEK composites. 

In a further study, DiMasi and colleagues investigated the kinetics of amorphous CaCOs formation at a fatty acid monolayer interface using synchrotron X-ray reflectivity measurements [173]. In-situ experiments found three different parameters that control CaCOs mineralization in the presence of arachidic acid monolayers, PAA, and Mg + ions. Firstly, the crystal growth rate depends on the concentration of counterions and not on the polymer concentration in solution. Secondly, the soluble polymer only affects the lifetime of the amorphous calcium carbonate. And finally, the sole effect of Mg + is to delay the mineral film formation. These data thus suggest that competitive adsorption (e.g. Mg + vs. Ca +) is another parameter to consider in controlled mineralization processes. 

Scheme 1 a Aggregation mode of interlayer micelle-occluded nanocrystals, b Graphic presentation of the formation mechanism of CaCOs mesorings. Gray, calcium carbonate red, hydrophobic block blue, soluble neutral block yellow, charged block. The red arrow indicates the decreasing gradient of occluded polymer within the disklike structure. (Reproduced from [156], 2006, American Chemical Society)... 

PCC (Precipitated Calcium Carbonate) is by definition a very fine, high purity processed calcium carbonate with controlled morphology, particle size and particle size distribution. PCC is often used in the production of paper [1], but can also be used in different fields of applications, mainly as fillers (in paints, polymers...). There is therefore a need for Lhoist to further improve its expertise in the field of synthetic carbonates and to develop innovative synthetic carbonates with new properties and especially new morphologies. For this purpose, an area in which Lhoist does not have much experience has been explored, that is the production of synthetic carbonates starting from a natural dolomite (CaC03.MgC03) instead of limestone (CaCOs). 

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