Fraunhofer IPA: paint savings on the example of a sledgehammer

How long does the paint stay flowing? How well does it level the bumps? Under what conditions does the desired mirror smooth surface form? “Previously, painters had to use costly and time-consuming trial and error to find out when a coat of paint was working best,” explains Dr. Fabiano Seer. In the Paint Visco project, he has now developed a simulation program with which the properties of paints can be virtually determined.

The development of the computer model was a challenge for the Fraunhofer IPA researcher and his team due to the viscoelasticity of the paints. Viscoelasticity, on the other hand, is key to predicting flow, that is, a paint’s ability to level out irregularities: these can be surface brush marks, but also pores, wavy structures and edges under the paint layer.

New measurement technology

Rotational rheometers determine the fluidity of paints by rotating or rocking a thin sample of liquid paint with a disk attached and then measuring the force required for deformation. “Previous devices, however, prevent evaporation of solvents, so the results have only limited significance for the coatings industry. Furthermore, such measurements always show only an arbitrarily selected small section of the material behavior, as the measurements are often performed with only a single frequency of vibration, ”Seeler reports. However, much more comprehensive information about the behavior of the material is required for the mathematical predictions of the course, for example the behavior of a paint sample at numerous frequencies.

Together with his team, he developed a new measurement technique. Nature was the inspiration: “We copied the measurement principle from bats,” recalls the researcher. The Paint-Visco-Rheometer works like a bat, with the frequencies merging fluently into each other. However, it is not the ultrasonic calls that are varied, but rather the frequencies with which the paint sample is deformed. By repeating the sequence of frequencies, it is possible to record the change in the properties of the viscoelastic varnish during hardening. With this special reporting module, all the necessary data for prognosis can be determined in a very short time, Seeler points out.

With the new measurement technology, the researchers at the Fraunhofer IPA can now also take into account the evaporation of the solvent, which is so important for the industry: in their rheometer, the paint layer is no longer deformed by a closed disc, but by a structure composed of several rings. The openings between the rings allow the solvent to evaporate.

For more information, see on the Fraunhofer IPA website.