Piezoelectric properties of poly(vinylidene fluoride) and carbon nanotube blends: beta-phase development

In order to get poly(vinylidene fluoride) (PVDF) films containing high beta-phase content, multiwalled carbon nanotubes (MWCNTs) were blended with PVDF. For drawn samples, the content of piezoelectric beta-form crystal was increased with MWCNT addition due to the rapid crystallization rate offered by the nucleating action of MWCNT, but soon reached a plateau. Poling on the drawn samples helps additional beta-phase formation when the added MWCNT content was less than 0.2 wt%; at this MWCNT amount, almost pure beta-phase crystal was obtained. More MWCNT addition induced depolarization to reduce the beta-phase content. Undrawn samples show monotonous increase of beta-phase content with MWCNT amount when subjected to poling.