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pps proceeding
Symposium: Rheology & Advanced Characterization
Oral Presentation
 
 

Polymer based coating analyses with diffusive wave spectroscopy

Ramsch Roland (1)*, Brambilla Giovanni (1), Fleury Mathias (1), Bru Pascal (1), Meunier Gérard (1)

(1) Formulaction - Haute-Garonne - France

This work presents the use of Diffusing Wave Spectroscopy (DWS) for film analyses such as aeronautical coatings. The method is based on the study of backscattered light, which gives information about the mobility of particles (contained in the product like droplets or fibres). The higher the mobility, the more fluid is the sample. By a simple data analysis, the technique allows to obtain typical drying kinetics of the coating as shown on the figure. Two new applications will be shown. Firstly, the impact of aeronautical coatings will be discussed. The number of layers spread on the aircraft have multiplied in recent years. Every layer has its specific function, and most often they are provided by different producers. Precoatings can significantly influence the drying behavior of the subsequent layer. In some cases the precoating retards the drying of the next layer, which leads to longer drying times. In this work, we will show how the DWS instrument Horus® can answer to this important issue, as it can measure the drying on the specific substrate, which is used for the application. The drying behavior of a polyurethane resin is analyzed on aluminum and on a pretreated aluminum substrate used in aeronautical industry. Secondly, a new approach of correlating characteristic drying times (open time) with the Persoz hardness. It was shown that the measured open time (around 10-60 min) of polyurethane/binder paints (2K) with different ratios of resin to binder correlate linearly with the corresponding Persoz hardness (measured at 180 hours). Form a calibration line of (5 to 6 ratios) one could extrapolate the Persoz hardness by this technique with only 1 hour of measurement.