XanoShear™ is a novel high-throughput, liquid-based method for the continuous production of staple polymeric nanofibers – in fact it is the world’s only commercial platform for controlled length polymeric staple nanofibers.
How It Works
The technology is based on hydrodynamic breakup of polymer solutions into small droplets, coupled with solvent attrition under shear in a viscous medium containing antisolvent.
The polymer droplets extend in parallel under shear stress in the bulk of the liquid, and precipitate forming nanofibers of lengths typically ranging from 10 mm to 5 cm.
These fibers can further be milled to staple fibers of shorter lengths (50 μm to 1 cm) allowing the fiber length to diameter (L/D) aspect ratios to be controlled.
Taking Wet Spinning to the Next Level
The XanoShear™ technology is based on a method invented in Professor Orlin Velev’s Laboratory at the Department of Chemical & Biomolecular Engineering in North Carolina State University (NCSU). The process is similar to traditional wet spinning where a polymer dissolved in a solvent is drawn through a solution containing an antisolvent. However, unlike wet spinning which can achieve minimum fiber diameters of ~ 10 μm, the ability to draw very thin fibers comes from the ultra-low interfacial tension between the polymer solution droplets and the medium, which allows high degree of stretching of the droplets and generation of nanofibers. The lack of nozzles typically required for nanomaterials production also allows massive parallelization and unprecedented throughput.
Benefits vs. Melt Blowing and Electrospinning
XanoShear™ opens new production capabilities beyond the two currently available commercial technologies for polymeric nanofiber production – meltblowing and electrospinning. Melt blowing and other similar approaches are based on mechanical drawing of polymer melts. Polymers are extruded from dies and stretched to smaller diameters by high-velocity, heated air streams, or centrifugal force.
Electrospinning uses electrostatic, rather than mechanical forces to draw the fibers onto a flat surface. Electrospinning can produce the smallest fibers (~ 40 nm in diameter) with narrow fiber diameter distributions, and is the only technique that can produce sub-micron fibers from most polymers.
While these technologies offer many advantages for several applications, the final form, a thin fused surface coating, limits their widespread use. In contrast, XanoShear fibers are collected as a wet cake, and as such can then be directed to many integrating processes such as wet laying, spraying, solids reinforcement, and powderizing to name a few. The ability to vary solvent and antisolvent type, mechanical and environmental conditions and shear profiles also opens the door to create nanofibers from polymers with extreme processing requirements not compatible with meltblowing or electrospinning.