Wetting of Pigment Particle Surfaces

The interactions between the surface of the pigment particles and their surrounding medium are of prime consideration in the wetting process and are optimized in the development and production of easily dispersible pigments. 

The energetics of the wetting of particles have been discussed extensively [61-63]. The specific thermodynamics of interfaces have been studied for a number of 

According to the above equation, the time t that is required to wet a powder is proportional to the viscosity of the surrounding medium, the depth of the pores, and the transported volume. The wetting time, on the other hand, is inversely proportional to the wetting tension — the driving force that promotes wetting — and to the cube of the radius of the pores in the agglomerates. 

Wetting out a pigment for several days by simply storing the manually prepared pigmented PVC paste (DOP content 39%) makes for almost optimum dispersion, which requires very little shear (see Fig. 88, p. 162). The wetting of the surface of the pigment particles by the plasticizer molecules thus determines the outcome of the dispersion process. 

Increasing the temperature frequently leads to better wetting, while the reverse is true for the mechanical breakdown of agglomerates. Similar observations have been made regarding the effect of wetting and dispersion agents [73]. 

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