THURSDAY, 17 MARCH 2011
Plastic polymers are widely used in electrical systems, from insulating wires and cables to organic solar cells. While generally stable, it is well known that these polymers can deform and fail if the voltage applied is too high.
In a study published in Physical Review Letters, polymers were spun into films supported on rigid substrates and their deformation was observed as a function of the applied electric field . The rigid substrates allowed the deformation process to be observed without breakdown occurring. For small voltages the polymer film remained flat and undisturbed. However, once a critical field was reached a regular pattern of creases formed due to the polymer folding. According to Xuanhe Zhao, one of the researchers behind this work, this creasing is analogous to bread rising. "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" . Increasing the field still further resulted in an increase in the size and number of the creases and eventually in craters evolving, due to electrical stresses pulling the creases open.
Understanding the breakdown process of the polymers will potentially allow for better insulating cables and polymer electronic devices to be designed, improving their performance and lifetime.
Written by Katherine Thomas