Pigment-Binder Interaction

The oil absorption gives the mass or volume of linseed oil required to form a coherent putty-Uke mass with 100 g pigment under specified conditions. The mixture should just not smear on a glass plate. For standards, see Table 1.1 ( Oil absorption ). Materials and apparatus rough glass plate, spatula with steel blade, raw linseed oil. 

Binder Absorption, Smear Point, and Yield Point 

Binder Absorption, Smear Point, and Yield Point [1.78]. Smear point and yield point are used to determine the binder needed to formulate a suitable millbase for grinding by dissolvers, roll mills, ball mills, attritors, sand mills, and pearl mills. The amount of binder is given in volume or mass units. Apparatus rough glass plate, spatula with steel blade. 

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Pigments can also influence other coating properties (e.g., film gloss) as a result of complex interactions between the pigment, binder, and solvent, and the method of application. 

A highly concentrated dispersion of carbon black is first prepared with a portion of the binder and solvent. The viscosity of this concentrate is a function of the particle size, structure, and surface chemistry of the black, the type of binder and its interaction with the pigment black, and the proportions of black, binder, and solvent. The final paint is made from the concentrate by adding more binder and solvent, its carbon black concentration is 3-8% referred to the solids content. Wetting agents are sometimes added to improve dispersibility and prevent flocculation. A number of concentrates for paint manufacture e.g., carbon black-nitrocellulose chips or carbon black -alkyd resin pastes, can be obtained from paint producers. 

Special effect pigments suitable for outdoor applications must meet the highest standards for color fastness and weather resistance. These pigments are coated additionally with thin layers of transparent and colorless oxidic compounds. These layers increase the light resistance by reducing the photoactivity of the titanium dioxide surface. In addition, the interaction between pigment and binder is optimized. 

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