Mechanical Performance of Macrofibers of Cellulose and Chitin Nanofibrils Aligned by Wet-Stretching: A Critical Comparison

Abstract

Renewable nanofibrillated cellulose (NFC) and nanofibrillated chitin (NFCh) are attractive fibrillar bionanoparticles due to their remarkable properties such as outstanding mechanical stiffness and strength, thermostability, barrier properties, and also for their global availability from renewable resources and food waste. One major bottleneck to maximize the mechanical properties of materials based on these bionanoparticles (e.g., nanopapers and macroscale fibers) is to find pathways to control their direction of alignment and understand how preferred alignment correlates with macroscale properties. Herein, we will demonstrate how strain-rate controlled wet-stretching of rehydrated macroscale fibers composed of nanofibrillated chitin and cellulose (NFCh, NFC) induces a high degree of orientation and how the degree of alignment scales with macroscale mechanical stiffness. We find similar degrees of alignment in both types of nanofibril-based macrofibers, yet substantially different macroscale stiffness, with the NFC-based fibers (E(NFC) = 33 GPa) outperforming the NFCh-based ones (E(NFCh) = 12 GPa) considerably. These differences can be correlated to the mechanical properties of the underlying cellulose I and α-chitin crystals and the degree of crystallinity of the nanofibrils, which both govern the stiffness of an individual nanofibril. Our study likely demonstrates the maximum performance in terms of stiffness of materials prepared by NFC and NFCh and reveals a critical difference in the performance of both classes of bionanoparticles.

Interfacial Polyelectrolyte Complex Spinning of Cellulose Nanofibrils for Advanced Bicomponent Fibers

“…17,61 The wet filaments were stretched at 4 % / min until rupture and the strain-at-break was recorded. The highest strains-at-break were reached with chitosan reaching 35 %, but a more repeatable 20 % was reached while using either PDADMAC or chitosan as the polycation.…”

“…Table S1). [15][16][17]20 . Fibers produced with microfluidics and oriented with flowfocusing show yield and ultimate tensile strengths notably higher, although Young's modulus remains similar to that of IPC spun TOCN/polycation fibers.…”

“…Fibers based on CNF or TOCN have aroused particular interest in the nanocellulose research community, due to the inherent suitability of cellulose to form strong fibers. [15][16][17][18][19][20][21][22] Especially, wet-spinning of CNF into a nonsolvent (i.e. coagulation bath such as ethanol or acetone) has been widely explored and exploited.…”

Chitin and Chitosan Nanofibers: Preparation and Chemical Modifications

“…The obtained chitin NFs formed a fine NF structure. Although conventional chitin is insoluble and precipitates in water, chitin NFs can disperse homogeneously, so the dispersion is easy to handle and to shape into desired forms depending on the application [55][56][57]. Commercial chitin and chitosan powders are also easily converted into NFs by mechanical treatment, since these powders consist of NF aggregates.…”

Water-Resistant, Transparent Hybrid Nanopaper by Physical Cross-Linking with Chitosan

“…Orientation can be induced in NFC films by drawing, as shown previously. 58,59 Therein, special care was necessary to draw neat NFC films in the wet state due to their mechanical weakness. In our case, the drawing has been considerably easier as the films are significantly stronger in the wet state than neat NFC films.…”