Dispersion effect of TEMPO oxidized cellulose nanofibrils on multi-walled carbon nanotubes

In order to research the dispersion effect of the different cellulose nanofibrils (CNFs) on the untreated multi-walled carbon nanotubes (MWCNTs), the CNFs with different carboxyl content and form were isolated from bamboo powder by 2,2,6,6-tetramethylpiperidin-1-oxyl radical (TEMPO) oxidation method with the different amount of NaClO added. The obtained different CNFs were used to disperse untreated MWCNTs as a dispersant, subsequently, the amount of MWCNTs dispersed in the different CNFs suspensions was measured with the Beer-Lambert law. The dispersion effect of the different CNFs on MWCNTs was evaluated by atomic force microscopy (AFM), laser particle size analyzer (LPSA) and so on. The results show that the carboxyl content of CNFs increases and the cross section diameter of CNFs decreases with the increase of NaClO added during TEMPO oxidizing. At the same time, the research also indicates that the dispersion amount of MWCNTs increases with the increase of the carboxyl content of CNFs. When the carboxyl content of CNFs increases from 0.635 mmol/g to 1.646 mmol/g, the percent of MWCNTs dispersed in the CNFs suspension increases from 19% to 39%. The different CNFs/MWCNTs suspensions show that the particle dispersion index (PDI) values of the particle size distribution are less than 0.3, and the absolute values of Zeta potential are higher than 30 mV, which proves that the MWCNTs could be well dispersed by the different CNFs. The CNFs/MWCNTs composite films display that the tensile stress increases and resistivity decreases with the increase of carboxyl group of the CNFs, when the carboxyl content of CNFs is 1.646 mmol/L, the tensile stress of CNFs/MWCNTs composite film can reach 91 MPa, and the resistivity is as low as 0.1460 Ωcm.