Mechanism of elementary events in the kinetics of electric failure of polymers

The kinetics of electric failure (breakdown) of PET and PP films 10–20 μm in thickness in a dc electric field at 77–340 K was studied. Two temperature intervals ∼340–200 K and ∼200–77 K were revealed. The durability and the breakdown field strength strongly depend on temperature at ∼340–200 K but not at ∼200–77 K. The mechanisms of elementary events that determine the process prerequisite to the breakdown of polymers are discussed; these are the thermofluctuation mechanism (electron hopping from trap to trap over the barrier) at elevated temperatures and the tunneling transit of electrons at low temperatures. The barrier heights (trap depths) of 1–1.5 eV and the elementary transit length of ∼1 nm were determined. The hopping transport of electrons in a field leads to the formation of critical space charges, which cause the breakdown of the polymer film.