Piezoelectric characteristics of electrospun PVDF as a function of phase-separation temperature and metal salt content

In this paper, the crystallinity changes in polyvinylidene fluoride (PVDF) as function of varying phase-separation temperatures (0 to 90 A degrees C) and chloride salts (BaCl2, CaCl2, CA degrees Cl-2, NaCl, SnCl2, N(2)H6Cl(2)) were investigated. FTIR quantitative analysis showed higher beta-crystalline and lower alpha-crystalline content for 70 A degrees C phase-separated PVDF and 70 A degrees C phase-separated PVDF-CaCl2 (15 wt%) samples. XRD and DSC studies also confirmed the influence of 70 A degrees C phase-separation temperature and CaCl2 salt in improving the beta-crystallinity in PVDF compared to the neat PVDF sample. Since higher beta-crystalline content is favoured for use in piezoelectric applications, these two sample preparation conditions were optimized for use in piezoelectric studies. Electrospun nanowebs of the selected samples were measured for their piezoelectric output signals under applied pressure of 1 kgf and released periodically at 0.5 Hz. From the peak-to-peak output voltage, 70 A degrees C phase-separated PVDF-CaCl2 sample exhibited significantly higher output voltage (+0.89 V) compared to neat PVDF (+0.48 V) and 70 A degrees C phase-separated PVDF (+0.53 V) samples. These results conclude that the combinative effect of phase-separation temperature and metal salt addition plays a vital role in improving the piezoelectric characteristics of PVDF, which signifies the importance of this study.