High performance nonwoven fiber production via UV-reactive and melt state centrifugal spinning
Nonwoven fibers have practical uses in diverse fields ranging from commodity products such as apparel, filtration, and hygiene products to advanced functional materials such as biomimetic scaffold materials, regenerative medicine, and optoelectronics. However, a need still exists to develop techniques to produce fibrous materials with high performance capabilities both economically and sustainably. Current synthetic fiber manufacturing technologies typically use either solvent or heat to transform a solid preformed polymer into a liquid before applying a force to draw the liquid into fiber. While the use of solvent poses concerns regarding process safety, environmental impact, and solvent recovery, the use of heat often leads to polymer degradation and excessive energy consumption. This dissertation attempts to address the challenging issue of producing high performance microfibers and nanofibers by using centrifugal spinning, an emerging technology and a promising manufacturing alternative to melt blowing and electrospinning. The intrinsically large centrifugal force leads to high throughput and low cost processing, while the capability to process both polymer melts and solutions demonstrates flexibility. The overall objective is to develop and optimize the centrifugal spinning process to generate novel multifunctional fibrous materials and to establish process-structure-property relationships. In this dissertation, a new fiber fabrication method combining centrifugal spinning and light initiated polymerization will be introduced. In contrast to traditional methods that utilize preformed polymers, the technique developed in this work produces fibers on demand from liquid monomer mixtures using only light to initiate polymerization. This method presents a potential route for green manufacturing of high performance fibers by reducing and even eliminating the use of both solvent and heat. The underlying physics and the principle parameters governing fiber formation, fiber morphology and fiber diameter are discussed. This knowledge is leveraged to develop new reactive monomer formulations containing high amounts of inorganic content in order to diversify the accessible material profile and enhance fiber properties. In addition, melt state centrifugal spinning of high performance materials with distinct properties is also discussed. Overall, the methods developed in this dissertation will provide key guidance for greener nonwoven fiber manufacturing while greatly expanding the ability to directly tailor fiber properties.