(443a) Nanofiber Production Via Melt Blowing
Melt blowing is a more than 50 year old polymer processing method for generating polymer fibers often as nonwovens. It employs a jet of hot air which creates an extensional force on an extruded polymer filament resulting in attenuation of its diameter by more than 1000 times in some cases. Although historically this method has been limited to the production of fibers exceeding 1-2 microns, we have recently (1) demonstrated the ability to produce long, defect free fibers several hundred nanometers in average diameter. Traditionally, electrospinning has been the only processing method available for producing fibers on this size scale. However, electrospinning is inherently less desirable than melt blowing due to its low production rate, solvent requirement, and high operating voltage. In this study, nanofibers were produced from commercial melt blowing grades of polypropylene and poly(butylene terephthalate) using a laboratory melt blowing device (both single- and multi-orifice) which was designed after commercial equipment. This demonstration of melt blowing capabilities is a step towards closing the gap between electrospinning and melt blowing in terms of the ability to produce nanoscale fibers. In addition, it highlights the potential for increasing the number of applications served by melt blowing. Finally, we have attempted to understand the ultimate limitations of this process by exploring the processability of a series of low and high molecular weight polystyrenes and their blends. Surprisingly, conditions can be identified where exceedingly low molecular weight polystyrene (Mn = 2.6 kg/mol and PDI = 1.09) can be readily melt blown into defect free fibers with an average diameter less than 1 micron. This result illustrates how much is yet to be learned about this process.
(1) Ellison, C.J. et al. Polymer 2007, 48, 3306-3316.