Understanding Polymer Deformation from Electric Voltages May Lead to More Durable Materials

Researchers at Duke University (Durham, NC) have discovered a method by which they can observe the real-time degradation of soft polymers caused by repeated exposure to electrical currents. This capability, according to the researchers, could aid in the development of more-durable polymers for applications in which they come into contact with electrical currents.

Common in polymers used for insulation in wires, cables, and capacitors, for example, this polymer breakdown was observed thanks to a novel setup created by the researchers. First, the researchers attached a soft polymer to a rigid polymer layer that acted as a protective substrate. Next, the team applied various electrical voltages to the combined polymer structure. The added substrate layer allowed for observation of the degradation process under a microscope without incurring a breakdown of the material, according to the scientists.

"As bread dough rises in a bowl, the top surface of the dough may fold in upon itself to form creases due to compressive stresses developing in the dough," explains Xuanhe Zhao, assistant professor of mechanical engineering and materials science at Duke's Pratt School of Engineering. "Surprisingly, this phenomenon may be related to failures of electrical polymers that are widely used in energy-related applications."

Zhao adds, "When the voltage reached a critical point, the compressive stress induced a pattern of creases, or folds, on the polymer. If the voltage is increased further, the creases evolved into craters or divots in the polymer as the electrical stress pulls the creases open. Polymers usually break down electrically immediately after the creasing, which can cause failures of insulating cables and organic capacitors."

This understanding of the degradation process, as well as the development of the more durable substrate structure, could someday enable the development of better polymers for insulation and electrical applications, including energy harvesting.

View a video of the deformation process below: