High Performance Fibers via Simultaneous Fiber Spinning and Photopolymerization
Prof. Chris Ellison
Dept. of Chemical Engineering & Materials Science
Univ. of Minnesota
Synthetic fibers have been manufactured for decades using solvents or heat to reduce the viscosity of pre-formed polymers and promote drawing. However, nature has engineered spiders and silkworms with benign ways of making silk fibers with high strength and toughness. Conceptually, their approach of chemically linking small functional units (i.e., proteins) into long chain molecules and solid fibrillar structures "on-demand'' is fundamentally different from current synthetic fiber manufacturing methods. Drawing inspiration from nature, a method will be described that uses light to trigger a thiol-ene photopolymerization to rapidly transform reactive liquid mixtures into solid thread-like structures as they are forced out of a capillary at high speeds. Besides being manufactured without using solvents/volatile components or heat, these fibers are mechanically robust and have excellent chemical and thermal stability due to their crosslinked nature. During processing, the balance between curing kinetics, fiber flight time, and monomer mixture viscoelasticity is essential for the formation of defect free fibers. This work focuses on developing a universal operating diagram to show how the intricate interplay of gel time, flight time, and fluid relaxation time leads to the formation of uniform fibers and also other undesirable fiber morphologies such as beads-on-string, fused fibers, non-uniform fibers, and droplets. This predictive capability enables adaptation of this spinning concept to all existing fiber spinning platforms, and customization of monomer formulations to target desired properties.
Chris Ellison is an Associate Professor and holder of the Piercy Professorship in the Department of Chemical Engineering and Materials Science at the University of Minnesota. From 2008-2016, he was a faculty member in the McKetta Department of Chemical Engineering at the University of Texas at Austin. He earned a B.S. in Chemical Engineering from Iowa State University and a Ph.D. in Chemical Engineering from Northwestern University. His group’s current research interests include structure, dynamics, and processing of micro- and nano-structured polymers, light-activated chemistry for thin film patterning and fiber manufacturing, and engineering sustainable processes and materials.