Cross-Linked Nonwoven Fibers by Room-Temperature Cure Blowing and in Situ Photopolymerization

Current synthetic nonwoven fiber production methods typically require transforming preformed polymers into a processable melt or solution state by heating or adding organic solvents, respectively, to facilitate fiber spinning. The significant energy demands and the use of volatile organic compounds render these processes suboptimal. Furthermore, conventional synthetic fiber manufacturing processes are limited to thermoplastics because cross-linked thermosets do not flow; however, the superior thermal and chemical resistance of cross-linked fibers render them attractive targets. In this study, we describe a "cure blowing" process that addresses these limitations by producing cross-linked fibers at room temperature with little or no solvent, using a lab-scale spinning die resembling those used for commercial melt blowing, an approach that currently produces >10% of global nonwovens. Specifically, a photocurable liquid mixture of thiol and acrylate monomers was extruded through an orifice and drawn by high-velocity air jets at ambient temperature into liquid fibers which were cross-linked into solid fibers by in situ photopolymerization during flight toward the collector. The effect of process parameters on the fiber diameter and morphology was investigated to understand the fundamental principles of cure blowing. Two intrinsic process limitations were identified in the drive to produce smaller yet uniform fibers, and strategies to circumvent them were identified. We anticipate that cure blowing may be an industrially relevant and environmentally friendly method for producing cross-linked polymeric nonwovens for a wide range of applications.