Calcium carbonate
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Calcium carbonate
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Color Index
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Pigment White 18
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Formula
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CaC03
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Structure
Calcium carbonate can be natural or synthetic. In its natural form, it is obtained
from chalk or limestone (purity = 98%). It can also be synthesized by calcination
of limestone. This synthetic form is called "precipitated calcium carbonate".
Concerning their structure, Limestone and Precipitated Calcium Carbonate have cubic
structures while Chalk can also have an amorphous structure.
Properties
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Properties of calcium carbonate
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Property
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Chalk
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Limestone
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PCC
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Density
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2.7
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2.7
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2.7
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Refractive index
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1.59
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1.59
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1.59
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Oil absorption
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15-20
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14-20
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high
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Acids resistance
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bad
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effervescence
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very bad
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Hardness
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2
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2
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3
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pH
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9-11
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Oil absorption
Because of their low oil absorption, they can be used at high levels. They impart
some structure to the wet paint by improving the stability to sedimentation of other
heavier pigments and imparting sag resistance in paint films.
Uses
Calcium carbonate is used in water- and solvent-based paints, for interior
and exterior decoration, and in many other coatings.
Price
These extender pigments are cheap.
