Fluidos aquosos baseados em poliacrilamida e nanotubos de carbono

Abstract

Fluids prepared with water, polyacrylamide (PAM) and carbon nanotubes (CNT) were studied viscosity and light scattering measurements. A previous characterization of PAM and CNT materials was also carried out. The carbon nanotube has a multi-walled structure, functionalized with 5% mass of acidic groups (MWCNT-COOH). Moreover, the CNT sample presents high purity (>95%), and diameter ranging from 5 to 10 nm. The polyacrylamides were characterized by NMR, CHN, TG, DSC, DLS1 and viscosity. Two fluid systems were investigated, one of them using commercial and the other one synthesized PAM. The difference between these two systems is the PAM characteristics. A commercial PAM, which is a copolymer of polyacrylamide containing 1 % acrylic acid (CPAM) and wM= 3.84 x 106 g.mol-1, was used at the concentration of 3 g.L-1 to produce the first set of fluids. The synthetic polyacrylamide (SPAM), Mw = 2.97 x 104 g.mol-1, was used to prepare dispersions in a concentration of 50 g.L-1. In both systems, the concentration of carbon nanotubes ranging from 0 to 1 % m/m (CNT/PAM). A decrease in the viscosity and an increase in the diffusion coefficient were observed for both fluids, as a function of CNT concentration . This can be explained by the reduction of the sizes of the polymeric coil (decrease in gyration radius) with increasing concentration of CNT. The results obtained from viscosity and light scattering showed a change of behavior at 0.2 m/m % of CNT for both systems, with different PAM. An abrupt decrease of viscosity and increase in diffusion coefficient was observed around this concentration. This may be consequence of the carbon nanotubes connecting polymeric coils, leading to group behavior in the diluted polymer concentration regime