Dispersion state of carbon nanotubes (CNTs) in cellulose nanofibrils (CNFs) film at variant sonication time in the presence of sodium dodecyl sulfate (SDS) has been studied in this work. The sonication was extended up to 120 min, and the CNF-CNTs-SDS suspension’s viscosity was measured at different times. Overall, viscosity of CNF-CNTs-SDS suspension decreased continuously as sonication continued except for the period of 60–75 min, where an increase in the viscosity was observed. Based on morphological investigations, the partial dispersion of particles at the early stage of sonication (i.e. up to 60 min) was followed by coagulation or reagglomeration of the particles during 60–75 min and increasing sonication time by 120 min led to improved dispersion of CNTs in CNFs. Likewise, the electrical conductivity and tensile strength obeyed the same trend due to improved CNTs-CNFs film’s network (30–60 and 75–120 min) and the corresponding reduction (60–75 min) caused by the partial agglomeration of CNT and CNF moieties. These findings highlight that sonication time is not a straightforward parameter and should be elaborated to reach the desired dispersion.

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