Organic Particles and Pigments

Suitability of Miciofluidic Devices for the Preparation of Organic Particles and Pigments... 

Pigments Aftertreatments. The surfaces of pigment particles can have different properties and composition than the particle centers. This disparity can be caused by the absorption of ions during wet milling, eg, the —OH groups, on the surface. In some cases, surfaces are modified intentionaHy to improve the pigments appHcation properties, interaction with the organic matrix, and weather resistance. 

Sedimentation analysis is suitable for a wide variety of materials and is used for both quaHty control and research work, such as agglomeration studies (56), and gives well-defined, relatively high resolution results. The technique has been employed in the evaluation of soils, sediments, pigments, fillers, phosphors, clays (qv), minerals, photographic haHdes, and organic particles (57,58). 

Because of the requirements of insolubility in water, in organic solvents and in the medium that it is being used to colour, the application processes for using pigments are quite different from those for dyes. Coloration with pigments is essentially a process of dispersion of solid particles of the pigment in a semi-solid medium. 

P.R.190 has a relatively small impact on the market. It is a specialty product for industrial paints, especially for automotive finishes, but offers no advantage over other members of its class. Its shade is dull and referred to as scarlet. In white reductions, the commercial type is very bluish and equally dull. The particle sizes of this product are too coarse for it to be used in metallic finishes. P.R.190 is very durable and very fast to organic solvents and to migration. The pigment is heat stable up to processing temperatures of 200°C. Despite its good heat stability, the pigment possesses only limited commercial value as a colorant for plastics. 

---