Competencies - Interface Control

Interface Control

Optimal dispersion and stabilization of pigment particles is a significant factor in determining the end properties of lacquers, paints, or printing inks. The pigments and fillers of the formulation must be ground to small-sized particles, wetted, and uniformly distributed as stably as possible. Only then can color intensity, gloss, hiding power, lightfastness, and weathering resistance be maximized. Pigment dispersion and stabilization, which require time and energy, are hardly possible without suitable wetting and dispersing additives.

TEGO® Dispers are high-performance wetting and dispersing additives for solvent- and water-borne formulations. Strongly reduced millbase viscosity permits high pigment loading during the grinding process. These additives are suitable for numerous organic or inorganic formulations as well as carbon blacks and matting agents.

Panta Rhei (Greek, meaning everything flows) certainly applies to paints and coatings. From manufacturing through storage and processing to drying or curing after application, many different demands are made on a coating or printing ink, depending on its flow properties. Characteristics which are affected include:

  • settling/sedimentation (important for storage stability) 

  • brushing resistance 

  • spattering 

  • sprayability 

  • sagging 

  • flow

Rheological additives can be roughly separated into inorganic and organic thickeners or thickeners for solvent-borne or water-borne coatings. Examples of modified inorganic thickeners for solvent-borne and water-borne systems include:

  • bentonite 

  • synthetic lattice-layer silicate 

  • pyrogenic silica (sometimes organically modified)

Examples of organic thickeners for solvent-borne or water-borne systems include:

  • polyureas 

  • cellulose derivatives 

  • polyamides

Examples of organic thickeners for water-borne coatings include:

  • associative thickeners 

  • non-associative thickeners

Evonik's TEGO® ViscoPlus product line offers a variety of polyurethane thickeners for use in water-borne systems, to control their rheological characteristics as well as to improve flow and leveling.

Competencies - Interface Control_2

AEROSIL® fumed silica is mainly used to control rheological characteristics, as a thixotroping agent, as an anti-settling agent, and to help in the prevention of rust and corrosion. Several hydrophilic or hydrophobic AEROSIL® fumed silica grades are available for a variety of applications.

AEROXIDE® Alu C, AEROXIDE® Alu 130, and the hydrophobic-grade AEROXIDE® Alu C 805 are well known to significantly improve the flowability, storage stability, and moisture uptake of powder coatings. AEROXIDE® Alu C is also able to positively influence the chargeability of Tribo powders.

A coating has a large interfacial area. Slip and flow additives are active at interfaces where, depending on their structure, they improve substrate wetting, promote flow, and add slip. Thus slip and flow additives significantly reduce any susceptibility to defects, resulting in a high-quality appearance and markedly improved scratch resistance, especially in freshly applied coatings.

The use of surfactants:

• improves substrate wetting

• improves flow

• generates a uniformly textured surface

• prevents floating of pigments and matting agents

• reduces sliding resistance

• improves scratch resistance

TEGO® Glide and Flow are highly effective flow additives that offer a high degree of compatibility with various coatings. Moreover, they are able to improve surface slip and anti-blocking characteristics at a very low level. Some are even crosslinkable and help to improve substrate wetting (TEGO® Rad, TEGO® Wet).