Comparative study of polyvinylidene fluoride nanofibrous membranes prepared by continuous near-field and conventional electrospinning processes

A comparative study utilising both continuous near-field electrospinning (CNFES) and conventional electrospinning processes of electrospun polyvinylidene fluoride (PVDF)-based membranes (EPMs) is presented in this Letter. The fibre morphology and average fibre diameter (AFD) of the EPMs are observed by scanning electron microscopy. Differential scanning calorimetry (DSC) is used to compare the possible modifications in crystal structure and thermal properties. Fourier transform infrared spectroscopy is used to study the crystalline isomers of PVDF EPMs. Results indicate that EPMs prepared by CNFES exhibit slightly lower relative intensities at the infrared absorption bands than the conventional electrospinning counterparts, owing to its smaller size of crystallite. Moreover, the CNFES electrospun fibres are revealed to have relatively higher crystallinity of 40.78%, as compared with conventional ones of 33.72%. However, DSC results indicate that both CNFES and conventional EPMs share similar thermographs in endothermic peaks extending from 156 to 174%C, despite the significant differences in AFD. Finally, the critical length of PVDF nanofibres is characterised experimentally and theoretical prediction of r∝z^-0.5 is in well agreement with the experimental observations of r∝z^-0.51.