Development of ultrafine nanofiber from polyacrylonitrile/ethylene co-vinyl alcohol precursor using solution electrospinning

Abstract

Abstract Ultrafine nanofiber from polyacrylonitrile (PAN)/ethylene co-vinyl alcohol (EVOH) with a diameter of a few hundred nanometers was prepared through solution electrospinning. In this study, EVOH was employed as a precursor for the purpose of decreasing the diameter of electrospun fibers. The effect of different EVOH content in weight percentages incorporated with PAN on the fiber diameters was investigated. A successive and drastic reduction in fiber diameter was observed with the increase of EVOH in the blend. Moreover, the fiber diameter was further reduced after isopropanol (IPA) treatment. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Fourier transform infrared (FTIR) spectroscopy were used to investigate the fiber morphology, thermal attributes, degradation behavior, and the chemistry of electrospun nanofiber respectively. The diameter of PAN/EVOH nanofibers found ranged from 47 nm to 880 nm, and after IPA treatment observed from 41 nm to 719 nm. The diameter of PAN/EVOH blend fiber was found to be 514 nm, 319 nm, and 116 nm for the EVOH content of 25%, 50%, and 75% correspondingly. After IPA treatment (at the content of 75%), the lowest PAN nanofiber diameter was discovered to be 102 nm. In the DSC heat flow, melting temperature (Tm) of electrospun nanofibers manufactured from pure PAN, pure EVOH, PAN/EVOH blend, and IPA treated were detected at 290 0C, 182 0C, 301 0C, and 271 0C separately. The blend nanofiber (50/50) exhibited a distinctive single melting peak in DSC and the Tm was shifted upward from 290°C (as observed in pure PAN) to 301°C. In addition, on the TGA curve the degradation temperature of blend nanofiber (50/50) extended up to 289°C which surpasses the pure PAN's value of 280°C. Both DSC and TGA analyses demonstrated the enhancement of the thermal properties of blend nanofiber. Due to its smaller diameter and improved thermal properties, the developed nanofiber may find use in air filtration and protective clothing.