Aggregation of Carbon Nanotubes in Semidilute Suspension

The CNTs aggregation in a low-viscosity PDMS matrix was studied from simultaneous time-resolved measurements of electrical conductivity and dynamic shear modulus. The concentration of nanotubes ( = 0.2%) was chosen in order to be in the semidilute regime of the suspensions. After a nonlinear compressive deformation, it was shown that the kinetics of CNTs aggregation strongly depend on the amplitude of the dynamic shear deformation. Actually, the kinetics of aggregation develops rapidly by increasing the deformation. However, above a critical deformation (?c = 60% corresponding to a critical Peclet number Pec ˜ 1×104), the equilibrium value of the storage modulus and electrical conductivity decreases with increasing the deformation. It was then concluded that low shear deformations induced an aggregation mechanism, but these aggregates broke down at high shear, forming small aggregates with less entanglements. Furthermore, this phenomenon of CNTs cluster aggregation was also highlighted by optical microscopy as the clustering mechanism of the CNTs was clearly observable after few hours.