Preparation Of Polyacrylonitrile Nanofibers Research Articles

Optimization of the preparation process of electrostatic-solution blow spinning nanofiber yarn using response surface methodology

There are several methods of preparing nanofiber yarns, but little work has been reported using a combination of electrospinning and solution blowing methods (i.e., electrostatic-solution blow spinning) to prepare nanofiber yarns. In this study, a response surface method (RSM) based on Box–Behnken design was used to investigate the relationship between the yarn parameters and yarn diameter, and the process was optimized. The yarn diameter was simulated by electrostatic voltage, air pressure, winding speed and funnel velocity. The correlation coefficients before and after adjustment were 0.97 and 0.95, respectively, through variance analysis, which verified the accuracy of the yarn diameter model. The results showed that the influence of each experimental factor on the yarn diameter was in descending order of winding speed, electrostatic voltage, airflow and funnel velocity, and there were interactions among the factors. The BDD response model was used to obtain the best experimental conditions, which provided a good theoretical reference for the preparation of polyacrylonitrile nanofibers. In addition, the effects of voltage and air pressure on the diameter of the nanofiber and yarn and the effects of the twist coefficient on the shape and mechanical properties of the yarn were studied. The results showed that with the increase of voltage and air pressure, the diameter of the nanofiber decreased, and the yarn diameter decreased first and then increased. When the twist factor was 100, the twist angle of the yarn was 49.91°, the breaking strength was 12.92 MPa and the elongation at break was 81.34%.

Preparation of Polyacrylonitrile Nanofibers by Solution Blowing Process

Solution blowing is an innovative process for spinning nanofibers from polymer solutions using high-velocity gas flow as fiber-forming driving force. Polyacrylonitrile (PAN) nanofibers were prepared using PAN solutions in N, N-Dimethylformamide and the morphologies of the fibers were examined using a scanning electron microscope. The process parameters including solution concentration, gas pressure supplied to the gas cavity, and solution-feeding rate were varied to investigate their effects on the morphologies of the fibers. PAN fibers were successfully prepared in the form of a nonwoven web. The fiber diameters mostly ranged in hundreds of nanometers and were affected by the process parameters. Results indicated that solution blowing is an alternative technique for manufacturing nonwoven webs that consist of micro- and nanofibers.

Preparation of Polyacrylonitrile Nanofibers with Controlled Morphology Using a Constant-Current Electrospinning System for Filter Applications

Polyacrylonitrile (PAN) fibers with average diameters in the range 100 nm with beaded morphology were prepared by a constant current electrospinning system. The fiber morphology could be easily varied by controlling the flow rate and electric current during the electrospinning process without changing the precursor solution. It was found that the use of lower flow rates resulted in more beaded fibers while the number of beads increases. The electric current could control the fiber morphology in which the beaded number (the number of beads or the beaded fibers) decreased as the electric current increased. It was also found that diameter and length of the beaded fibers increases as the electric current increases. Therefore, these results are able to be applied to find optimal conditions in obtaining high performance filter media.

Preparation of polyacrylonitrile nanofibers as a precursor of carbon nanofibers by supercritical fluid process

A simple method for the preparation of polyacrylonitrile (PAN) nanofibers using a supercritical fluid technique, rapid expansion of a supercritical solution into a liquid solvent, is reported. It was found that PAN fibers having the size range of 50–300 nm in diameter were obtained when a solution of supercritical carbon dioxide and dimethylformamide mixture containing PAN was rapidly expanded into an ambient aqueous NaCl solution, at a pre-expansion pressure and temperature of 20.7 MPa and 60 °C, respectively. The effect of polymer concentration on the formation of nanofibers vs. nanoparticles was investigated. The morphological analysis by field emission scanning electron microscopy revealed that PAN nanofibers were exclusively obtained at higher polymer concentrations whereas aggregated nanoparticles were produced by lower concentrations of PAN in the supercritical solution. Using the PAN nanofibers as precursors, carbon nanofibers were obtained by the pyrolysis at 800 °C under N 2 atmosphere.