Carbon nanotubes power strong and tough aramid fibers

The synthetic high performance fiber has excellent mechanical properties and has broad application prospects in the field of impact protection. However, manufacturing high-strength and high-toughness fibers is challenging due to the inherent conflict between them. In this paper, we report that by polymerizing a small amount of (0.05 wt%) short-aminated single-wall carbon nanotubes (SWNTs), the strength, toughness and modulus of hetero-ring aramidon fiber are increased by 26%, 66% and 13%, respectively, with a tensile strength of 6.44±0.11 GPa and a toughness of 184.0±11.4 MJ m−3. Young's modulus is 141.7±4.0 GPa. The mechanism analysis shows that short-aminated single-walled carbon nanotubes can improve the crystallity and orientation by influencing the structure of the heterocyclic aramide chain around the single-walled carbon nanotubes, and in-situ polymerization can increase the interfacial interaction between the single-walled carbon nanotubes, promote stress transfer, and inhibit strain localization. These two effects are responsible for the simultaneous increase in strength and toughness.

Preparation and properties of composite fiber, schematic diagram of polymerization and spinning process of composite fiber. b Stress-strain curves of HAFs and sa-SWNT-HAFs. The illustration shows digital photos of HAFs and sa-SWNT-HAFs. c Radial comparison diagram of mechanical properties of HAFs and sa-SWNT-HAFs. d Comparison of tensile strength between HAFs and sa-SWNT-HAFs at different strain rates. The error bar represents the standard deviation of the tensile strength.

Structural design and characterization of single-wall carbon nanotubes, schematic diagram of sa-SWNTs. b High-resolution transmission electron microscopy (TEM) images of the original single-walled carbon nanotubes. Scale, 50 nm. c Scanning electron microscope (SEM) image of the original single-walled carbon nanotubes. Scale, 10 μm. d SEM images of sa-swcnts. Scale, 10 μm. e X-ray photoelectron spectroscopy (XPS) of different swcnts. The blue stripe indicates the location of the n1 s peak. f n1s XPS spectrum of sa-SWNTs. g Raman spectra of different carbon nanotubes.

Mechanical properties of composite fibers, a comparison of tensile strength and modulus of different fibers. b Comparison of elongation at break and toughness of different fibers. c Comparison of tensile strength and modulus of SA-SWnT-HAFs at different sa-swnt concentrations. d Comparison of elongation at break and toughness of SA-SWnT-HAFs at different sa-swnt concentrations. All error bars represent standard deviations. Comparison of specific tensile strength and elongation at break of e commercial high performance fibers with our prepared fibers. The measurement data are derived from the composite filament test. f Specific energy consumption power (SEDP) of different optical fibers. The data of trigonometric symbols in the figure come from literature.

The strengthening mechanism of sa-SWNT-HAF, the relationship between the influence range of crystallization zone and the increase of Young's modulus. b Mass density distribution and snapshot of the effect of sp2 carbon sheet on heterocycle aramid chain at room temperature. c Binding energy of typical polymer chains on sp2 carbon sheets. d Simulation snapshots of HAFs, sc-SWNT-HAFs, and sa-SWNT-HAFs under tension.