Aligned Electrospun Nanofibers for Nanocomposite Applications

摘要

Electrospinning is a rapidly developing technology that provides a unique way to produce novel polymer nanofibers with diameters from 50 nm to 500 nm. Electrospinning was first patented in 1934 by Anton Formhals. Since then electrospun fibers have been used in various applications including biomedical, filtration media, ceramics and composites. In the electrospinning process the polymer solution or melt is usually contained in a syringe - like apparatus. A metering pump attached to the plunger of the syringe generates a constant pressure and flow of the fluid through the syringe. The polymeric fluid being used is 10 wt % poly vinyl alcohol (PVA) in water which was prepared by vigorous mixing and constant heating at 90 °C for 12 hours. The driving force of the jet is provided by two high voltage sources. The high voltage sources can generate up to 30 kV DC, and the setup can be run on positive or negative polarity or a combination. A total of 8 kV was applied over a distance of 8 to 12 cm to produce uniform fibers. A combination of positive polarity at the syringe and negative polarity at the collector has proven to yield the most predictable fiber morphology. Adjusting the flow rate of the fluid and the magnitude of the electric field controls the spinning rate which influences fiber size. A syringe pump rate of 0.2 ml/hr through a 20 gauge needle tip has been employed. Through careful control of the experimental parameters, aligned fibers with a narrow width distribution can be obtained. Aligned nanofibers are essential for developing high strength nanocomposites. Formation of aligned fibers was demonstrated by harvesting the fibers that spanned the gap of a C-shaped collector. Collecting the fibers across a void gap enables the fibers to be easily gathered for future processing and evaluation. Morphological studies have been performed using an Electroscan 2020 Environmental Scanning Electron Microscope (ESEM).