| Résumé : |
Thickening additives have a major infulence on the storage stability and processing properties of liquids systems. They have always been an important component in the formulation of sovant-based coatings. Back at the coating formulation stage, they help to optimise energy introduced in the milling phase, thus enhancing dispersibility. At the same time, they improve storage stability by reducing the sedimentation tendency and syneresis. In the industrial application of such systems, they imrove leveling and reduce yhe sagging tendency of the coatings.
With the increasing demand for low-VOC or VOC-free water-borne coating systems, there has been a call for a new class of thickeners - known as modern rheological aditives. These additives allow specific modification of the viscosity of the system at various shear rates. As a result, such key coating properties as vertical flow, leveling, gloss, film thickness, covering power, spattering tendency, brush and roll resistance, sedimentation tendency and pigment stabalization - to mention only some of the most important - are significantly affected.In most cases, only small quantities of between of 0.1 and 4%, calculated on the formulation, are enough to obtain ideal flow properties for a particular application. In addition, such additives also make recommendations on the choice of suitable systems with the aid of a few selected examples. |
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Role and function of rheological additives in modern emulsion paints and industrial coatings in PAINTINDIA, N° spécial (02/2002)
