Electrospun poly(vinylidene fluoride) membranes functioning as static charge storage device with controlled crystalline phase by inclusions of nanoscale graphite platelets

Abstract

Caused by the nature of polymorphism of poly(vinylidene fluoride) (PVDF), crystalline transformation could significantly influence the properties of PVDF. In this work, electrospun PVDF membranes were studied for their tensile properties and static charge storing capacity with controlled crystalline phase. The crystallinity was found to be influenced by inclusions of nanoscale graphite platelet (NGP). Bead-free nanofibers with uniform structure were determined by scanning electron microscopy (SEM). Structural and intermolecular characterizations were performed by SEM and Fourier transform infrared spectroscopy. Analyses of thermal properties were carried out by using differential scanning calorimetry and thermogravimetric analysis. Experimental results showed that NGP inclusions significantly changed the crystallinity of the PVDF nanofibers by inducing a transition of α-crystalline phase to β-crystals and, therefore, increased the thermal stability of the electrospun membranes. Tensile properties of PVDF membranes with and without NGP inclusions were evaluated by a universal testing system. Due to the increased fraction of β-crystals, the tensile strength, failure strain and Young’s modulus of the composite membrane (NGP0.75) were improved by 31.2, 20.5, 132.4%, respectively, in contrast to virgin PVDF. This result indicated the significant development of small fractions of NGP on the tensile properties of the PVDF nanofibers; moreover, the static charge storage ability of electrospun membranes with and without NGP inclusions was evaluated and showed an enhancement caused by the increased β-crystals fractions.