K. Song, W. Xu
Arizona State University,
Keywords: fibers, composites, spinning
Summary:As two-dimensional (2D) nanolayered materials, graphene layers tend to fold, wrinkle, and crimple when embedded in polymer materials and lose their intrinsic mechanical, electrical, and thermal reinforcement properties. This study demonstrated a few examples of exfoliating stacked graphene layers and orienting them along with specific directions. (i) The first example was about the inclusion of graphene platelets (GNPs) between polyvinyl alcohol (PVA) materials in fibers. The GNPs formed step-wise exfoliation with controlled shear stress and aligned with the fiber axis. As a result, the composite fibers showed enhanced composite mechanics. (ii) The exact alignment mechanism in a different polymer, thermoplastic polyurethane (TPU), showed enhanced functionality. Besides, with high stretchability and diffusion-dependent absorption, these fibers were susceptible to mechanical strains and volatile gases. (iii) Graphene layers were also known for their template effects on polymer crystallization. Thus, we included graphene in polyacrylonitrile (PAN) and formed graphitic structures in PAN/GNPs composite fibers. The precursor fibers showed much higher modulus and strength with layer creation in fibers. These fibers are highly potential for high-performance carbon fibers. These demonstrations of forming flat graphene with preferential alignment showed flexible nanoparticle morphologies and broad applications when 2D material morphology is precisely manipulated.