Viscoelastic and Rheological Properties of Carboxymethyl Cellulose /Starch/Graphite Oxide as Superabsorbent Hydrogel Nano Composites (SHNCs)

Abstract

Uncross-linked carboxymethyl cellulose (CMC) / starch blend used to prepare two hydrogels; the first is cross-linked CMC / starch with aluminum sulfate octadecahydrate cross-linker and the second is SHNCs manufactured from incorporation of 0.3wt% nano graphite oxide (GO) in the above cross-linked blend. Viscoelastic and rheological properties of these two hydrogels were studied and compared with the uncross-linked blend. Results showed that the cross-linking process increases the blend miscibility and converted it to miscible blend. The SHNCs hydrogel has the higher Tg and the uncross-linked blend has the higher Tan δ. GO addition causes increment in some viscoelastic parameters such as G*, G', and G, and decrement in damping parameters and make the damping behavior more stable at lower frequencies, and causes increment for all rheological parameters (η* , ηo, ηf , and GNo). GO addition leads, also, to the absence of the shear thickening behavior and increases both the entanglement density and the molecular weight average. Both hydrogels exhibited broad molecular weight distribution (MWD) and highly cross-linking degree and their elastic behavior predominates; makes them rigid specially at higher frequencies.