On the effect of carbon nanotubes on the rheological and viscoelastic properties of an aqueous polyacrylamide solution
M.I. Pryazhnikov, E.N. Volchenko, S.D. Kazanina, A.V. Minakov
Siberian Federal University, Krasnoyarsk, Russia
Keywords: Polymer solution, polyacrylamide, rheology, viscoelasticity, carbon nanotubes, elastic modulus, viscosity modulus
Abstract
This paper presents the results of a comprehensive study of the rheological and viscoelastic properties of aqueous polyacrylamide (PAA) solutions modified with single-walled (SWCNTs) and multi-walled (MWCNTs) carbon nanotubes. The study was conducted on a modular rheometer at 25°C. It was found that all studied compositions based on 0.05 wt.% PAA exhibit pseudoplastic behavior and are characterized by a predominance of elastic properties over viscous ones in the linear shear strain range. The addition of CNTs has been shown to significantly alter rheological properties. With increasing nanotube concentration, an increase in effective viscosity and consistency parameters is observed, along with a decrease in the flow index. The viscoelastic moduli (G′ and G′′) also increase, demonstrating a nearly linear dependence on the CNT content. A fundamental difference in the effectiveness of the two types of nanotubes was revealed. SWCNTs exhibit a significantly stronger modifying effect compared to MWCNTs. Thus, at the same concentration of 0.1 wt.%, the consistency parameter of the solution with SWCNTs is 2.2 times higher, and the elastic modulus G, is 3.15 times higher than the values for the polymer solution with MWCNTs. This is due to the exceptionally high aspect ratio of SWCNTs, which ensures the formation of a strong percolating network at lower threshold concentrations. The results of the study demonstrate the high potential of carbon nanotubes for controlling the rheology of polymer solutions.
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