Synthesis and processing of solution spun cellulose acetate fibers reinforced with carbon nanotubes

We report the fabrication of Cellulose Acetate (CA) based fibers reinforced with Multi-Walled Carbon Nanotubes (MWCNTs) using a solution spinning process. The motivation of this work is to produce high performance fibers based on sustainable natural materials as an alternative to synthetic fibers for structural applications. A 30 wt% solution of CA in a binary solvent system of N, N-dimethylacetamide (DMAc) and Acetone (3:7 v/v) was used for the solution spinning of CA fibers. Both neat and CNT-loaded CA fibers were produced. The CNT loading with respect to the polymer was at 0.5 wt%. For CA-MWCNT spinning solutions, the MWCNTs were initially dispersed in the solvent and then CA is added and mixed together. The mixing temperature kept 40-45°C. The viscosity of the CA solution was 8,000 cP. Addition of MWCNT increased the viscosity of the CA solution to 32,000 cP. A lab-scale solution spinning line consisting of a constant torque high temperature gear pump and heated extrusion channels was used to produce both neat and CA-MWCNT fibers. The solution was pumped through a spinneret at the end of the extrusion channel with an orifice as a viscous gel-like filament which was passed through a spool placed in a coagulation bath and then it formed as fiber. The fibers are collected to a takeup roll at a draw ratio of 8.0. Characterization studies of both neat and MWCNT loaded fibers were performed differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA) and scanning electron microscopy (SEM). DSC analysis of fibers showed reduction in crystallinity of CA upon inclusion of 0.5 wt% MWCNT. TGA analysis showed improvement of thermal stability in CAMWCNT fibers compared to neat CA. Cross-sections of neat CA fibers showed smooth surfaces with no significant defects, while CA-MWCNT showed formation of micro-voids and irregular features. Longitudinal views of outer surface of both neat CA and CA-MWCNT fibers showed no indication of surface defects or protrusions.