Paint formulations require rheology modifiers to adjust flow properties during manufacturing, storage as well as application. Although representing typically less than 1% of the formulation, the rheology modifier determines to a large extend main paint properties such as storage stability, ease of application, sag resistance, flow and leveling.Rheology modifiers are used in coating materials and paints to give the system wanted rheological characteristics. The rheology of a coating material relates to storage, processing as well as application conditions. A wide range of rheology modifiers is made available, most of these with very specific features and benefits. This article reviews specific properties of main classes, including cellulose and associative thickeners, as used in aqueous systems, up to polyamides and organoclays as used in solvent-borne paints and coatings. Furthermore, various measurement procedures are being proposed, as well as basic selection criteria for rheology modifiers in relation to various paint systems.
posted by Titus Sobisch, R&D - Applied/ Formulation/ Product development at L.U.M. GmbH
Dear Johan Bieleman,
thank you for this interesting overview.
Associative thickeners ...'contribute to almost Newtonian flow behavior'. Is there no option to obtain shear thickening properties? However, later it was stated 'Associative thickeners contribute to strong high shear thickening'. Please clarify.
Relating to the solvent born coatings it would be helpful to give additional information in which solvent systems the different additives work (best). Cannot imagine that all perform best in more polar and in rather apolar systems as well.
In relation to organoclays we observed that in connection with aromatic solvents swelling of the inner layers occurs, which should also contribute to the thickening effect.
I would like to add that multisample analytical centrifugation can be a useful efficient means to evaluate the effect of rheology modifiers, especially in relation to stability.
By the way the use of the term PVC is a little bit confusing for me as this first hand suggest a polymer not 'pigment volume concentration'.