Authors Wulf, M. ; Uhlmann, P. ; Michel, S. ; Grundke, K.
Title How levelling additives affect the film formation of powder coatings
Date 03.08.2000
Number 9243
Abstract Adhesion quality and optical appearance of powder coatings are determined by film formation. Melt surface tension of the coating is one parameter that plays a decisive role in this process. In order to control and to adjust melt surface tension, levelling additives have to be added to a powder coating formulation, otherwise surface defects like craters or wavy surfaces (orange peel effect) will result. Most of the current knowledge regarding the effect and surface activity of these additives in powder coatings is based on trial and error. However, a more fundamental and quantitative understanding is desirable for developing new, superior additives for improved powder coating formulations. In the current study, the influence of additive properties like molecular weight and chemical structures (polyacrylates and polyestermodified polysiloxanes) on surface tension of typical powder coating binders is studied systematically by means of a new technique based on Axisymmetric Drop Shape Analysis (ADSA) in a temperature range from 140°C to 185°C. It is shown that all additives considerably decrease the surface tension of the binder. In addition, notable differences in the effect of the two groups of additives (acrylates and polysiloxanes) were found. The consequences pertaining to film formation of powder coatings are discussed. Furthermore, results of AFM phase imaging measurements are presented. This technique provides qualitative information about the lateral distribution of the additives at the binder surface.
Publisher Modern Paint & Coatings
Citation Modern Paint & Coatings 90 (2000) 16-20
Tags PG_SurfaceTension

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