Supporting the electromechanical nature of ultra-fast charge pulses in insulating polymer conduction

The generation and transport of ultra-fast charge pulses is a new conduction mechanism in insulating polymers, which is related to the electromechanical property of polymers. An investigation of fast space charge dynamics in pure and nanofilled epoxy resin at different temperatures is presented in this paper. Experimental observations show the appearance of ultra-fast charge pulses, which cause heterocharge accumulation at electrodes. Mobility and repetition rate of both positive and negative fast pulses decrease with increasing nanoparticle concentration. Their temperature dependence was also determined. The influence of nanoparticles on dynamic-mechanical properties is studied to investigate the relation between charge dynamics and the chain relaxations. The values of activation energy for pulse mobility, repetition rate and loss modulus support the speculation that in epoxy based nanocomposite the mechanism of the ultra-fast charge pulse injection is associated with the β mechanical relaxation. Transport of positive pulses seems to be governed by the same mechanical relaxation as injection, while the transport of negative pulses is probably driven by a different process. An explanation for the variation of fast charge pulse characteristics is given in terms of the different morphological effects of nanoparticles on epoxy resin.