Failure modes in piezoelectric poly(vinylidene fluoride)

This article describes a number of potential failure mechanisms for piezoelectric poly(vinylidene fluoride) (PVDF), including decay of piezoelectric properties, film shrinkage at elevated temperatures, electrode erosion due to water, curling and fibrillation of the highly oriented PVDF films, and abrasion or impact damage. Piezoelectric aging and shrinkage are found to be strongly correlated; neither process occurs below 60°C, and both show logarithmic time dependences above that temperature. Thus, shrinkage and piezoelectric aging likely both result from similar mechanisms associated with micro‐structural annealing effects at elevated temperatures. The degradation of piezoelectric response observed when PVDF films are exposed to moisture is found to be due primarily to water‐induced erosion of the vapor‐deposited aluminum electrodes rather than to enhanced piezoelectric decay. Observations of mechanical damage suggest that the susceptibility of PVDF films may be partially due to imperfections introduced during the manufacturing process. One conclusion of this study is that biaxial PVDF offers advantages over uniaxial film, including reduced shrinkage and piezoelectric decay, superior resistance to curling and fibrillation, and lower susceptibility to formation of pinholes and other localized defects.