Melt-Spun Nanocomposite Fibers Reinforced with Aligned Tunicate Nanocrystals

• Main Authors: Alexandre Redondo, Sourav Chatterjee, Pierre Brodard, LaShanda T.J. Korley, Christoph Weder, Ilja Gunkel, Ullrich Steiner
• Format: Article
• Language: English
• Published: MDPI AG 2019-11-01
• Series: Polymers
• Subjects: cellulose nanocrystals (cncs); polyurethane; nanocomposite fibers; melt-spinning; reinforcement; orientation; thermal stability
• Online Access: https://www.mdpi.com/2073-4360/11/12/1912

The fabrication of nanocomposite films and fibers based on cellulose nanocrystals (P-tCNCs) and a thermoplastic polyurethane (PU) elastomer is reported. High-aspect-ratio P-tCNCs were isolated from tunicates using phosphoric acid hydrolysis, which is a process that affords nanocrystals displaying high thermal stability. Nanocomposites were produced by solvent casting (films) or melt-mixing in a twin-screw extruder and subsequent melt-spinning (fibers). The processing protocols were found to affect the orientation of both PU hard segments and the P-tCNCs within the PU matrix and therefore the mechanical properties. While the films were isotropic, both the polymer matrix and the P-tCNCs proved to be aligned along the fiber direction in the fibers, as shown using SAXS/WAXS, angle-dependent Raman spectroscopy, and birefringence analysis. Tensile tests reveal that fibers and films, at similar P-tCNC contents, display Young’s moduli and strain-at-break that are within the same order of magnitude, but the stress-at-break was found to be ten-times higher for fibers, conferring them a superior toughness over films.