The relative dielectric constant r

The relative dielectric constant r and dielectric loss tangent of PVDF and P(vdf-trfe) 75/25 mol% are shown in figure 4. As can be seen from FIG. 4 (a) and (c), the dielectric constant r of all membranes decreases with the frequency from 100 Hz to 10 MHz, which is related to the decrease of dipole response at high frequencies [21]. In addition, when the temperature is below 100℃, the tangent of PVDF and P(vdf-trfe) 75/25 mol% membrane increases with the increase of frequency, as shown in figure 4 (b) and (d). When the temperature is higher than 110℃, due to the increase of relaxation of dipoles at high temperature and the increase of conduction loss caused by impurity ions and defects, the loss tan is opposite to the change trend of temperature and increases with the frequency. Therefore, the stretch PVDF and P(vdf-trfe) 75/25 mol% membrane has a tan greater than the high frequency measured results at low frequencies [22]. The dielectric temperature spectrum can also be used to analyze the performance of ferroelectric phase transition of the polymer. See figure 4(a). The dielectric peak of r of stretched PVDF occurs in the temperature range of 60~80℃, and the peak temperature increases gradually from 100 Hz to 10 MHz with the frequency, which corresponds to the ferroelectric-paramedical phase transition [23]. However, as shown in figure 4(c), the dielectric constant r of the P(vdf-trfe) membrane at 120 ° c has a higher strength and a narrower shape than that of the stretched PVDF, which also corresponds to the ferroelectric-paramectric phase transition (f-p phase transition) and reaches 200 at the constant r at 100 Hz. In addition, when the r and tan of the stretched PVDF and P(vdf-trfe) membranes were higher than 150 ° c, other peaks appeared. This peak was the sample melt peak Tm, which was consistent with the results measured by DSC diagram.