Читать книгу Additives for Water-borne Coatings - Wernfried Heilen - Страница 42

Wetting and dispersing additives fulfil different functions within a coating formulation. They help pigment wetting and stabilise the dispersed pigment particles. They reduce the grinding time and decrease the viscosity. The dosage of additive has different influences on properties of the grind such as:

 viscosity

 colour strength

 compatibility

 storage stability.

The surface tension has a major influence on pigment wetting. In water-borne formulations two stabilising mechanisms are used:

 steric stabilisation

 electrostatic stabilisation.

The structure of wetting and dispersing additives is determined by the pigment wetting required, the anchoring to the pigment surface and the pigment stabilisation. The structures are mostly surfactant-like.

Depending on requirements different chemical structures are available. The simplest are based on fatty acids. Higher demands can be fulfilled by acrylic- and maleic-anhydride copolymers.