To coat automobile exteriors, making their appearance more attractive.
* While a particular model/version may be used as an example in this method, any current or past model/version from the same series may also be used. Please consult a sales associate to discuss the most current instrumentation and software available.
These are methods of testing paints at high shear rates. Paint is often tested at these high shear rates (10,000 -12,000 s-1), to simulate the shear rates that paints undergo while it is being sprayed. The test methods that we used were based upon the standard test methods set forth by ASTM D 4287 (common standard in North America) which is run at 12,000 s-1, and the standard test methods set forth by ISO 2884 and BS 3900 (common standards in Europe), which are run at 10,000 s-1.
We used a High Torque CAP 2000+L viscometer, with Capcalc v3.0 software for automated instrument control and data acquisition. We used Cone°1 to achieve on-scale results, with 67 ?L of fluid. The cone and plate were cleaned before dispensing each paint portion. A fresh portion of sample was used for each trial. Three trials were done for each speed. We equilibrated the sample and cone for 30 seconds prior to testing. The solvent trap was used to help prevent evaporation. Representative data from the analyses are shown in Figures 1, 2, and 3 below:
Figure 1: Black Auto-Refinishing Paint, at 25°C.
Figure 2: Black Auto-Refinishing Paint, at 25°C.
The tolerance for the High Torque CAP 2000+L Viscometer running at 750 RPM with cone°1 is +/-5 cP, and the tolerance for the High Torque CAP 2000+L Viscometer running at 900 RPM with cone°1 is +/-4.16 cP. Figures 1 and 2 show that results obtained with the High Torque CAP 2000+L Viscometer were repeatable within the tolerance of the viscometers.
Figure 3: Paint Standard Test Method Comparison.
Figure 1 shows the data obtained by the standard test method described by ISO 2884. This standard test method is more commonly used in Europe. Figure 2 shows the data obtained by the standard test method described by ASTM D 4287. This is a standard test method more commonly used in North America. Figure 3 plots Run 1 of Figures 1 and 2. Figure 3 shows that the viscosity obtained by the various tests produces similar data. For further detail about the testing methods used refer to ASTM D 4287and ISO 2884.
The slight increase in viscosity over time may be attributed to solvent evaporation from the paint sample.
Acknowledgement: We thank Clifford M. Schoff, Ph.D., for his helpful technical discussions concerning this work.