QUESTION:

How to fix a static electricity problem?

An overhead projection (OHP) foil created too many paper jams in a copier, therefore the surface layer composition had to be improved. The root cause was identified as a static electricity problem. Static electric charge arose from the friction of the OHP foil with the components in the copier. This is called tribo-electricity.

However, quantitative determination of tribo-electric properties is known to be difficult as a result of poor reproducibility of this kind of measurements that largely depend on environmental conditions. Our HT lab was asked to develop a robust method to determine relative improvement of tribo-electric properties of test coatings for product optimization.

APPROACH:

HT lab to the rescue

Rather than trying to control all environmental variables in the tribo-electric experiment (which are hardly controllable), the approach was to run all tribo-experiments in the HT lab at the same time and in parallel. This way, differences in the environmental variables cancel out and relative changes are detected without doubt.

Sets of candidate coating solutions were collected and drop-coated as array on a carrier foil. The carrier foil was mounted on a measurement cylinder. Then, by continuous rotation of the carrier foil against a charging cylinder, the set-up was brought into a quasi-continuous experimental state and the resulting surface charge could reproducibly be measured over the complete array of drop coatings. Control of the apparatus and display of the measurement results were realized in LabView.