Simultaneously Enhanced Tenacity, Rupture Work, and Thermal Conductivity of Carbon Nanotubes Fibers by Increasing the Effective Tube Contribution

Abstract

Although individual carbon nanotubes (CNTs) are superior as constituents to polymer chains, the mechanical and thermal properties of CNT fibers (CNTFs) remain inferior to commercial synthetic fibers due to the lack of synthesis methods to embed CNTs effectively in superstructures. The application of conventional techniques for mechanical enhancement resulted in a mild improvement of target properties while achieving parity at best on others. In this work, a Double-Drawing technique is developed to deform continuously grown CNTFs and rearrange the constituent CNTs in both mesoscale and nanoscale morphology. Consequently, the mechanical and thermal properties of the resulting CNTFs can be jointly improved, and simultaneously reach their highest performances with specific strength (tenacity) $\rm\sim3.30\,N\,tex^{-1}$, work of rupture $\rm\sim70\,J\,g^{-1}$, and thermal conductivity $\rm\sim354\,W\,m^{-1}\,K^{-1}$, despite starting from commercial low-crystallinity materials ($I{\rm_G}:I{\rm_D}\sim5$). The processed CNTFs are more versatile than comparable carbon fiber, Zylon, Dyneema, and Kevlar. Furthermore, based on evidence of load transfer efficiency on individual CNTs measured with In-Situ Stretching Raman, we find the main contributors to property enhancements are (1) the increased proportion of load-bearing CNT bundles and (2) the extension of effective length of tubes attached on these bundles.