where k is the consistency index (Pa·sn), which is related to themagnitude of the shear viscosity; n is the power lawindex, ranging between 0 and 1, i.e. it is equal to 1 for Newtonian behavior and decreases with increasing the non-Newtonian behavior. The fitting curves are shown in Fig. 1(b). The power law model parameters k, n, and R2 were summarized
in Table 1. From the curves and the R2 values (R2 ≈ 1), it can be seen that the flow behavior of all the solutions fits well with the power law model. k value increases from 0.2971 to 1.2445 with the HNTs content, which suggests that the solution viscosity increases by the addition of nanotubes. This result is consistent with the previously reported composite systems inwhich the addition of particles into polymers leaded to an increase of the k value [40,41]. Both pure SA and SA/
HNTs solutions are shear thinning and have n b 1. The n value of the mixture solutions is lower than that of pure SA solution especially at high HNTs loading (except the SA2N1),whichmay be related to the formation of filler networks at high nanoparticle loading in the polymer matrix. The decrease trend of the n value was in accord with the polymer-
clay (montmorillonite) composite systems [42].