Calcium carbonate CaCO coatings

The egg shell is 94% calcium carbonate [471-34-17, CaCO, 1% calcium phosphate [7758-23-8] and a small amount of magnesium carbonate [546-93-0]. A water-insoluble keratin-type protein is found within the shell and in the outer cuticle coating. The pores of the shell allow carbon dioxide and water to escape during storage. The shell is separated from the egg contents by two protein membranes. The air cell formed by separation of these membranes increases in size because of water loss. The air cell originally forms because of the contraction of the Hquid within the egg shell when the temperature changes from the body temperature of the hen at 41.6°C to a storage temperature of the egg at 7.2°C. 

Prominent markets today for fine CaCOs are as fillers in paper, paint, PVC, rubber, putty, cosmetics, and toothpaste and as an antacid and a calcium supplement in foods. Surface-coated grades are also produced and are more easily dispersed in organic materials. CaCOs is also used to coat paper, and its use as a filler has increased rapidly with the increase in alkaline papermaking. Many small precipitation plants now operate at papermill sites. Controlled precipitation of calcium carbonate allows control of crystal geometry and particle size distribution. This allows custom production with attractive properties for various markets. With the recent expansion in precipitated calcium carbonate capacity, there are fewer possibilities for disposal of the relatively low-quality material from a brine plant. 

Surface treatment of CaCOj can change its nucleating activity in iPP. In Reference [134] iPP composites with nano-CaCOs were modified with iPP grafted with acrylic acid (PP-g-AA). of iPP in the composites increased with increasing nano-CaCOs content, and it was further increased by the addition of PP-g-AA. Recently, composites of iPP with 1 wt% and 3 wt% of nanosized calcium carbonate, both calcite and aragonite, coated either with PP-g-MA or fatty acids were... 

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