Through orthogonal experimental methods, the melt electrospinning of pure phenolic fibers has been achieved. The preparation is based on an orthogonal experimental method, which was designed to investigate the optimal conditions for production through integrated effects of spinning temperature, gap between spinneret and collector, as well as applied voltage. We found that optimal spinning conditions at 1608C, a spinneret-to-collector gap of 8 cm, and applied voltage at 40 kV produce an average electrospun fiber diameter reaching 4.44 6 0.76 lm, with narrow variance distribution. The fibers were cured in a solution with 18.5% formaldehyde and 12% hydrochloric acid, heated from room temperature to 808C and maintained 1h. In this report, the morphology, structural changes, and heat resistance of the fibers are characterized. Obtained results reveal that curing the fiber reduces crystallization and improves heat resistance.

In order to overcome the difficulty of reducing fiber diameters during melt electrospinning, a pulsed electric field is applied. The effect of the frequency and duty cycle of the pulsed electric field on the fiber diameter, crystallinity, and molecular orientation was studied. Results revealed that the diameter of the poly-L-(lactic acid) (PLLA) melt electrospun fiber was reduced by this pulsed electric field, especially at higher frequencies, and the finest fiber was obtained at a duty cycle of 29.8% and a frequency of 1 kHz. Both constant and pulsed electric fields can lead to a high molecular orientation in electrospun fibers, particularly in the crystalline regions. In addition, the molecular orientation and crystallinity of the fibers can also be improved by increasing the frequency and duty cycle of the pulsed power. Of note, fibers with multiple necking structures were interestingly observed at field frequencies of 8 and 10 kHz at the microfiber scale.

Getting finer fibers is one important goal of electrospinning. In this article, we introduce orthogonal experimental research of solution electrospinning with a pulsed electric field. The influences of the voltage, flow rate, frequency, and duty cycle on the mean diameter and diameter distribution of electrospun fibers were investigated. The phenomenon of electrospinning in a pulsed electric field was compared to that of electrospinning in an ordinary electric field. We found that the order of the factors that affected the fiber diameter was Duty cycle > Flow rate > Voltage > Frequency and the order of factors that affected the fiber diameter distribution was Duty cycle > Flow rate > Frequency > Voltage. In addition, compared with the ordinary electric field, the pulsed electric field apparently contributed to reductions in the mean fiber diameter and diameter distribution. In this article, we provide important evidence for the reduction of the fiber diameter with the pulsed electric field. V C 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46130.

Phenolic fiber is a versatile material. This article focused on introduction of the progress of generating phenolic fibers using solution electrospinning method and its applications, as well as the trail exploration of preparing phenolic fibers by melt electrospinning. For the research on preparation of phenolic fibers using solution electrospinning, researchers added polymers or additive agents to adjust the viscosity and electrical conductivity of the spinning solution. Then they cured and carbonized the electrospun fibers to reach their varied aims. After these two processes, the brittle nature of the phenolic fibers has been greatly changed. What’s more, the modification makes it easier to be dealed with in the analysis tests and be more suitable to be applied as adsorbent materials, nonconductive materials, and flexible materials.