The role of sag control agents in optimizing the sag/leveling balance and a new powerful tool to study this

In order to obtain glossy coatings with a high quality appearance it is necessary that surface irregularities created during paint application or during drying/curing of the paint level-out sufficiently while sagging problems are avoided. We have recently developed the so-called falling wave method that can be used to determine the sag and leveling behavior of wet paints during drying and curing in a quantitative manner. This method is very useful in identifying the cause and nature of poor coating appearance and facilitates development of paints with good sag and leveling behavior.In this paper, it is shown that thixotropy of the paint can be very useful in increasing sag resistance, improving coating appearance and widening the application window. Thixotropy can be introduced in paints by addition of, e.g. sag control agents. Various experimental examples of the beneficial use of sag control agents on the sag/leveling behavior of paints are given.