This technology can be applied to make polymer nano-fibers with mechanical properties comparable to conventional high-performing fibers. These fibers might be used to develop all-polymer composites for use in body armor.
Conventional high-performance polymer fibers are produced using a process known as mechanical gel spinning. These fibers have excellent mechanical properties such as modulus and strength. However, gel spinning is unable to produce fibers with sub-micron diameters due to limitations in the ability of mechanical systems to exert the larger hydraulic forces required and to interface with sub-micron scale fibers.
On the other hand, electrospinning has been used to produce sub-micron fibers for a range of applications ranging from filter to battery materials. However, conventional electrospun fibers have inferior mechanical properties that prevent their use in applications that demand high mechanical resilience, such as textiles.
This invention describes a hybrid gel electrospinning process capable of producing sub-micron fibers with mechanical properties comparable to conventional high-performance fibers.
In the novel process described by the Inventors, a polymer filament is first formed using conventional electrospinning. Subsequently, the filament undergoes electrostatically driven drawing and whipping processes that stretch the fiber and reduce its diameter to sub-micron levels. Unlike conventional electrospinning, the drawing and whipping processes take place at elevated temperatures. The process temperature is chosen to induce the formation of a gel solution region within the fiber being spun, which increases the degree of molecular orientation in the resulting fiber and improves its mechanical properties. For example, the Inventors have successfully produced UHMWPE fibers with a diameter of 0.3 µm and a Young’s modulus of approximately 120 GPa -- comparable to that of conventional Spectra fibers.
Superior mechanical properties compared to conventional electrospun sub-micron fibers
Orders of magnitude higher productivity compared to production of high-performance sub-micron fibers by tip drawing