During the application of FBE (Fusion Bonded Epoxy) coatings, the powder must melt, flow and cure completely before quenching. The minimum melt viscosity that the material achieves during application is important in determining the ability of the material to form a contiguous layer and to form adhesive bonds with the substrate. If the minimum melt viscosity is too high, the coating material will not form a contiguous layer. On the other hand, if it is too low, the coating layer may not be uniform. One way to determine the required minimum melt viscosity is to mathematically model a well characterized high performance FBE formulation made with an epoxy resin having a similar backbone structure and functional groups as that used in the formulation(s) under evaluation. Using rheology and kinetic models, the rate of reaction and flow behavior of four different FBE formulations, specifically designed for an application temperature of 180 deg C, have been evaluated. The predicted performance of these formulations was compared against the predicted performance of a standard FBE formulation, which is known to produce a good coating at an application temperature of 240 deg C. The LAT-3 formulation had a predicted minimum melt viscosity close to the control formulation. The LAT-3 formulation also had the best flexibility, as predicted, of all the LAT formulations evaluated. A temperature sensitivity study was conducted, using the bar bending test, to determine the application temperature range. The analysis showed that the LAT-3 formulation would provide a high performance FBE coating within the application temperature range of 163-204 deg C. The temperature sensitivity study also showed that the flexibility of the coatings decreased slightly as the minimum melt viscosity increased. This increase in minimum melt viscosity is due to the decrease in the application temperature. Reducing the application temperature below 163 deg C resulted in incomplete cure which was detrimental to the flexibility of the coating. In conclusion, this study demonstrates that rheology and kinetic modeling can be used to evaluate the ability of FBE to form a uniform film that cures within the processing time commonly used in the pipe coating industry. Furthermore, the minimum melt viscosity is an important parameter in determining the ability of FBE to form a contiguous and high performance coating
Rheokinetic modeling of fusion bonded epoxy powder coatings at standard and low application temperature
Rheokinetische Modellierung der Epoxidharzpulverbeschichtungen bei Standard- und geringer Anwendungstemperatur
2009
11 Seiten, 5 Bilder, 2 Tabellen, 11 Quellen
Conference paper
English
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