Effect of molecular weight on the dielectric breakdown strength of ferroelectric poly(vinylidene fluoride-chlorotrifluoroethylene)s

The dielectric strengths of poly(vinylidene fluoride-chlorotrifluoroethylene) copolymers have been investigated as a function of molecular weights (MW) at different temperatures. We have shown that the electrical breakdown strength increases with increasing MW and decreasing temperature. Experimental measurements of the electrical breakdown field at 25 degrees C agree fairly well with an electromechanical breakdown model. The dielectric breakdown at lower temperatures near and below the glass transition is attributed to the existence of thermal breakdown process, which is supported by numerical calculations and experimental measurements. (C) 2007 American Institute of Physics.