Dispersing agent requirement

Testing procedure. Water is added to a blender, followed by ammonium hydroxide to adjust pH to the required level. Carbon black is added in 30 s with low speed mixing. Dispersing agent is added in portions from a burette under high speed dispersion. The endpoint is determined as 5 min of uninterrupted fluidity under high speed mixing. The total time of determination should not exceed 10 min. Standard methods. The method is described in Cabot Corporation Technical Report S-131. 

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Figure 13.4. Dispersion agent requirement vs. pH in water dispersions of carbon black. [Adapted, by permission, from Foster J K. Sims, E S, Polym. Paint Col. J., 184, 1994, 312.]...

The usual problems encountered with any sedimentation procedure are present. It is necessary to use a dispersing liq compatible with the material being tested. Also, dispersing agents and technique must insure complete dispersion and prevent agglomeration. These factors may vary with materials, and therefore will require special attention when new materials are to be analyzed... 

Evaporators require the continuous low level (1-3 ppm) application of a suitable antisealant chemical treatment. Traditionally, polyphosphate has been used (sometimes in conjunction with an antifoam and/or a dispersant agent), but it generally performs poorly because of a lack of thermal stability. Treatments based on polymaleic acid (PMA) and other modem organic polymers tend to perform much better. 

TABLE 1 Lime Soap Dispersant Requirement (LSDR) of Various Types of Lime Soap-Dispersing Agents (LSDAs)... 

When Fast Colour Salts are used hydrochloric acid and sodium nitrite are obviously not required, although some Fast Colour Salts do need an addition of acetic or formic acid. The nonionic dispersing agent is still necessary but as most Fast Colour Salts contain an alkali-... 

Spray drying requires formulahon of a relatively stable, usually aqueous dispersion of zeolite and colloidal binder particles, which are then fed to the spray drier [88, 89], Organic dispersing agents may be added to the spray drier feed slurry to stabilize the dispersion while the slurry is fed to the drier. 

Slurry explosives are based upon a system consisting of oxidizing agents and nonexplosive fuel materials. The explosive energy derived from these unique explosives is the result of extremely rapid reduction-oxidation reactions between the fuels and oxidizers upon initiation by a high explosive booster. A slurry explosive can be visualized as a colloidal system which comprises basically two phases, a dispersion phase and a dispersed phase. Tire fundamental concept which led to the discovery of slurry explosives was that an aqueous oxidizer solution (eg ammonium nitrate) could be used as the dispersion medium of a colloidal system to disperse the required fuel (aluminum) and thereby achieve a multiplicity of beneficial results... 

When polymers are used as constituents of coatings, paints, and lacquers, they require solvents as dispersing agents. Whether true solutions are formed or emulsions, the solvents used have to conform to environmental specifications, but should be sufficiently volatile so as to permit rapid drying of the applied polymer and pigment, if present. One should examine chapter 6 and the appendix for green examples of coatings solvents. 

Suspensions are manufactured either by a precipitation or by dispersed methods requiring use of suspending agents whose characteristic can significantly change because of the presence of other components such as electrolytes. 

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