Organic pigments

25 ноября, 2015

Pokraskin

Organic pigments are a vast class offering a large number of pigments with varying hues and chroma. Organic pigments gained importance in the coating industry due to restrictions on some inorganic pigments containing heavy metals as well as due to their high color purity and tinctorial strength compared to most inorganic pigments. Some important pigmentary properties of organic and inorganic pigments are compared in Table 3.6.

Organic pigments are synthesized from different petrochemical intermediates; therefore, thousands of molecules are possible due to wide latitude in selection of petrochemicals, but only a few hundred are commercially produced that have balanced price and performance. Discussing all the pigments individually is outside the scope of this book; therefore, selected important organic pigment families are briefly discussed here.

Table 3.6: Important properties of extenders

Property	Organic pigment	Inorganic pigment
Color	Bright	Dull (mostly)
Light and weather fastness	Varies	Usually excellent
Tinting strength	High	Varies
Opacity	Usually lower	Usually higher
Solvent fastness	Extremely varies	Excellent
Particle size	Usually smaller	Usually larger than organic
Ease of dispersion	Varies	Much easier than organic
Thermal stability	Varies	Usually higher than organic
Surface type	Hydrophobic	Generally hydrophilic