Cellulose Fiber with Enhanced Mechanical Properties: The Role of Co-Solvents in Gel-like NMMO System

Abstract

Cellulose has garnered attention in the textile industry, but it exhibits limitations in applications that require high strength and modulus. In this study, regenerated cellulose fiber with enhanced mechanical properties was fabricated from a gel-like N-methylmorpholine N-oxide (NMMO)-cellulose solution by modulating the intermolecular interaction and conformation of the cellulose chains. To control the interaction, two types of co-solvents (dimethyl acetamide (DMAc) and dimethyl formamide (DMF)) were added to the cellulose solutions at varying concentrations (10, 20, and 30 wt%). Rheological analysis showed that the co-solvents reduced the solution viscosity by weakening intermolecular interactions. The calculated distance parameter (R_a) in Hansen space confirmed that the co-solvent disrupted intermolecular hydrogen bonding within cellulose chains. The solutions were spun into fiber via a simple wet spinning process and were characterized by X-ray diffraction (XRD) and universal testing machine (UTM). The addition of co-solvent led to an increased crystallinity index (C.I.) owing to the extended cellulose chains. The modulus of the resulting fiber was increased when the co-solvent concentration was 10 wt%, regardless of the co-solvent type. This study demonstrates the potential for enhancing the mechanical properties of cellulose-based products by modulating the conformation and interaction of cellulose chains through the addition of co-solvent.

Keywords: N-methylmorpholine N-oxide; cellulose; co-solvent; conformation; fiber; gel-like solution; mechanical property; rheology.

Figure 1

Rheological properties of solutions with different cellulose concentrations. (a) Zero-shear viscosity. (b) Vial inversion test of each solution.

Figure 2

Polarized optical images of cellulose and co-solvent-added solutions. (Control: cellulose sample without co-solvent, Ac: dimethyl acetamide (DMAc), F: dimethyl formamide (DMF), and x (10–30): the wt% of the co-solvent).

Figure 3

Apparent viscosity of co-solvent-added cellulose solutions. (a) Dimethyl acetamide. (DMAc). (b) Dimethyl formamide (DMF).

Figure 4

Viscoelastic properties of the solutions. (a) Dynamic sweep test results and (b) frequency at crossover-point (ω_C) plotted against the content of the co-solvents.

Figure 5

Fourier-transform infrared spectroscopy (FT-IR) graphs of (a) regenerated fibers and (b) pristine materials.

Figure 6

Microstructure of the regenerated fibers. (a) X-ray diffraction (XRD) patterns. (b) Crystallinity index.

Figure 7

Mechanical properties of the regenerated cellulose fibers.