No abstract

Conventional electrospinning is a simple process, suitable for the processing of solvated polymers at relatively low rates. It lacks the capabilities of conveying of solids, mixing of polymeric resins and devolatilization and has limited capabilities in melting and incorporation of fillers, including nanoparticles. The use of a twin screw extruder as the front end of the electrospinning process provides these capabilities but only becomes feasible at relatively high throughput rates. Such high rates of electrospinning can only be achieved by using multi‐nozzle spinnerets. However, the dynamics of electrospinning processes using multi‐nozzle spinnerets has not been well studied. Here a multi‐nozzle spinneret attached to a hybrid twin screw extrusion and electrospinning apparatus was employed for the characterization of the dynamics in terms of the electrospun mesh thickness distributions of poly(caprolactone), PCL, as a function of the principal parameters of the electrospinning process, i.e., applied voltage, distance of separation between the spinneret die, and the collector, i.e., a conductive mandrel, and its rotational speed. PCL fiber diameter and orientation distributions, as well as the thickness, crystallinity, and mechanical properties of the non‐woven meshes, were characterized to gain a basic understanding of how the electrospun mesh properties develop as a function of process parameters in the multi‐nozzle configuration. ENG. SCI., 2013. © 2012 Society of Plastics Engineers

A new type of material, a "nanobursa" mesh (from "bursa" meaning "sac or pouch"), is introduced. This material consists of sequential layers of porous polymeric nanofibers encapsulating carbon nanotubes, which are functionalized with different metal nanoparticles in each layer. The nanobursa mesh is fabricated via a novel combination of twin-screw extrusion and electrospinning. Use of this hybrid process at industrially-relevant rates is demonstrated by producing a nanobursa mesh with graded layers of Pd, Co, Ag, and Pt nanoparticles. The potential use of the fabricated nanobursa mesh is illustrated by modeling of catalytic hydrocarbon oxidation.

Non-woven nanoporous membranes of poly(caprolactone), PCL, incorporated with multi-walled carbon nanotubes, CNTs, could be fabricated via an industrially-scalable hybrid twin screw extrusion and electrospinning process. The utilization of a spinneret with multiple nozzles allowed the increase of the flow rate beyond what is possible with conventional electrospinning using a single nozzle, albeit at the expense of difficulties in the control of the thickness distributions of the nanofibrous membranes. The thickness and orientation distributions and the resulting mechanical properties of the membranes could be modified via changes in voltage, angular velocity of the collector mandrel and separation distance of the collector from the spinneret. The increases in crystallinity due to the presence of the CNTs and the preferential alignment of the nanofibers via rotation of the collecting mandrel led to increases in the tensile properties of the nanoporous membranes. The use of poly(ethylene oxide), PEO, together with PCL, followed by the dissolution of the PEO, rendered the nanofibers themselves nanoporous with typical surface porosity values of around 50% and pore sizes of about 220 nm. The demonstrated versatility of the hybrid twin screw extrusion and electrospinning process and the manipulation of mesh dimensions and properties are indicative of the applicability of the hybrid process for fabrication of nanoporous membranes for myriad diverse industrial applications ranging from water treatment to tissue engineering applications.