Rheological studies of semidilute polyacrylamide/carbon nanotube nanofluids

The rheological behavior of aqueous nanofluids formed by polyacrylamide (PAM) and different concentrations of carbon nanotubes (CNT) has been investigated. The overlap concentration, molecular size, and mass of PAM were first obtained from viscometry of dilute samples. Determination of the critical concentration of PAM directed the preparation of nanofluids at distinct semidilute regimes: 3.0 g L−1 and 6.0 g L−1. The slow diffusivities inferred from dynamic light scattering experiments were closely correlated with null stress viscosity extrapolations. The controlled degradation of PAM through sonication was also studied. Thoroughly dispersing MWCNT-COOH in semidilute solutions of PAM led to an improvement in viscosity of approximately 40 %.