Rheobyk 425 (formerly BYK 425)

Rheobyk 425 (formerly BYK 425) is a VOC-free, liquid rheology additive for aqueous dispersion-based systems which improves anti-sagging and adjusts in-can viscosity. The resulting increase in viscosity simultaneously improves the storage stability with reduced settling.

The additive is suitable for increasing the grinding viscosity of aqueous pigment pastes.

The rheological effectiveness of Rheobyk 425 is primarily based on the associative interaction with the dispersion particles of the aqueous binder and enables a highly pronounced pseudoplastic flow behaviour.

The urea modification of the additive also causes an increase in the rheological effect via hydrogen bonds.

Rheobyk 425 is VOC- and APEO-free, does not impair gloss, and its rheological effect is not dependent on the pH value.

It is suitable for all kinds of aqueous coatings, printing inks, and adhesives. When grinding pigment pastes, the additive can also increase the millbase viscosity and therefore improve the dispersion conditions.

For formulations with a considerably lower application viscosity (eg coatings for conventional spraying), it is recommended to use Rheobyk 425 together with Rheobyk 420 (or Rheobyk D 420 or Rheobyk 7420 ES), as the anti-settling properties are much more pronounced.