Space charge distribution and mechanical properties in plasticized PVC actuators

In our last paper, we have reported that due to the polarization properties of the plasticized polyvinyl chloride (PVC gels), the low energy ion irradiation made an internal negative charge accumulate on the gel surface near the anode. It then resulted in the creep deformation of PVC gel along the anode. In this paper, the small force generated by an applied electric field was measured by an innovative force device designed with high load precision. The pulsed elect-acoustic (PEA) method was used to investigate the space charge distribution of PVC gels with various contents of plasticizer BDA under an electric field. As a result, the stress occurring in PVC gels by an electric field could be measured with a high precision and a linear relationship between stress and strain was obtained. It was found that the stress and strain generated in PVC gels depended deeply on the applied DC voltage. Young's modulus of three PVC gel materials depended on the ratio of DBA to PVC content and would not be affected by the magnitude of applied electric field within 2 kV DC voltages. In the measurement of space charge distribution, it was found that the pure PVC film was of the almost same space charge distribution when DC voltages changed. For the plasticized PVC, the negative accumulation charges were observed with the increment of DC voltages. Besides the DC voltage, the content of plasticizer DBA had a great influence on the curves of negative accumulation charges. The charge density peak and negative charge band were proposed as the effective parameters to represent the characterization of negative accumulation charge curves, which were mainly contributed by material structure and material properties in PVC gels. It was shown when DBA content in PVC gels was in 25 to 50 weight percentage, the negative accumulation density became a high value. This may be the reason why a PVC gel has actuation behavior. Based on the polarization of PVC gels, the negative accumulation charge and the mechanical response under an applied electric field, a deformation model was proposed for better understanding actuation mechanism of PVC gels.