Influence of Spinning Voltage and Solution Concentration on Insulating Oil Regeneration by PVDF Nanofibers

Abstract

Traditional insulating-oil-regeneration methods have been found inefficient and unable to clear fine particles and acid degradation products. This work aims to improve the oil-regeneration performance of Poly(vinylidene fluoride) (PVDF) nanofibers by variable electrospinning voltages and PVDF solution concentrations. The PVDF/dimethylformamide (DMF) solutions of varying concentrations were utilized for electrospinning at different electric voltages. Results from Fourier-Transform Infrared (FTIR) spectrum and Scanning Electron Microscopy (SEM) show that with the increase of PVDF concentration, the crystalline a phase in the nanofibers was seen gradually decreased, while the β phase got increased. The increased voltage from 16 to 20 kV led to decreased nanofiber diameter and narrowed diameter distribution. However, a high voltage above 20 kV has led to the opposite tendency. After filtration by the nanofibers prepared at 20 kV and 14% concentration, the AC breakdown voltage of the aged oil shown 52.5% enhanced, and the relative permittivity ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> as well the loss factor tanδ of the aged oil decreased distinctly to the level which is comparable to new insulating oil. The electrospun PVDF nanofibers have shown good performance on the regeneration of aged insulating oils. The electric voltage and the solution concentration during electrospinning are critical to optimizing the regeneration performance of the nanofibers.