Abstract
Response surface methodology (RSM),based on five-level, four variable Box-Benkhen technique was investigated for modeling the average fiber diameter of electrospun polyacrylonitrile (PAN) nanofibers. The four important electrospinning parameters were studied including applied voltage (kV), Berry's number, deposition distance from nozzle to collector (cm), and spinning angle (circle minus in degree). The measured fiber diameters were in a good agreement with the predicted results by using RSM technique. High-regression coefficient between the variables and the response (R-2 = 87.74%) indicates excellent evaluation of experimental data by second-order polynomial regression model. The optimum PAN average fiber diameters of 208 and 37-nm standard deviation were collected at 19 kV, Berry's number = 10, 25(degrees) spinning angle, and 16-cm deposition distance. The PAN/N,N-dimethylformamide (DMF) polymer solution with the optimum weight concentration (10 wt.%) was selected to study the effect of dispersing exfoliated graphite nanoplatelets (EGNPs) in PAN/DMF solution on the electrospun EGNP/PAN fibril composite diameter. Five different EGNPs weight concentrations (2, 4, 6, 8, and 10 wt.%) were dispersed in the optimized PAN/DMF polymer solution. Morphology of EGNPs/PAN fibril composites and its distribution were investigated by scanning electron microscopy (SEM) to show the minimum fiber diameter for the above-mentioned 5 wt. % of EGNPs. A minimum fibril composite diameter of 182 nm was obtained at 10 wt.% of EGNPs. Morphological characteristics of electrospun fibers and their distribution were tested by Raman spectroscopy, SEM, differential light scattering, and high-resolution transmission electron microscopy.