Immobilization of carbonized polyacrylonitrile on the structure of carbon nanotube fibers for improved mechanical performance

Carbon nanotube fibers (CNTF) have great application potential in flexible electronics, smart wearables, bioelectrodes due to their excellent mechanical/electrical properties. However, CNTF is assembled by a large number of CNT monomers, and loose combination of these monomers usually weakens its mechanical/electrical properties. In this study, referring to the principle of carbon fiber precursor carbonization, the carbonization of PAN (polyacrylonitrile) was used to encapsulate and fix the CNTF precursor prepared by floating catalytic chemical vapor deposition to enhance CNTF mechanical performance. Firstly, PAN with different mass fraction was selected as sizing agent to treat the twisted fiber(CPAN@CNTF), then carbonized heat treatment was carried out at different temperatures. Through analyzing the enhancement effect of the structural changes of PAN on the mechanical/electrical properties of CNTF under different conditions, then, the mechanical properties of CNTF reached the best when the PAN sizing amount was 10 wt.% and the heat treatment temperature was 320ºC, and the breaking strength of CNTF was increased to 480 MPa, which was 44% higher than that of untreated CNTF group. It is found that the elastic recovery degree of slurry CPAN@CNTF is excellent through thermomechanical stretching, indicating that PAN after pre-oxidation and low temperature carbonization has a stable effect on the structure of CNTF.