Preparation and Rheological Properties of Konjac Glucomannan/Surface Deacetylated Chitin Nanofiber Composite Gels

The microstructure and properties of composite gels prepared from konjac glucomannan (KGM) and surface deacetylated chitin nanofibers (S-ChNF) at different concentrations were studied. The results showed that the KGM/S-ChNF composite gel was a pseudoplastic fluid with shear thinning nature, which conformed to the power law model. With increasing S-ChNF concentration, the gel’s viscosity increased, its shear stress decreased, its viscosity coefficient increased from 23.174 Pa·sⁿ to 29.950 Pa·sⁿ, and its flow index decreased from 0.43663 to 0.41308, indicating enhanced pseudoplasticity. Dynamic viscoelastic analysis showed that both the storage and loss moduli were dependent on angular frequency, and displayed an increasing trend with increasing S-ChNF concentration. In addition, the crossing point moved from 6.77 s^-1 to 3.77 s^-1, indicating that the intermolecular hydrogen bonding was enhanced, increasing the resistance to KGM molecular chain movement and prolonging the relaxation time. Consequently, the gel tended to be an elastic fluid. The results of Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and thermogravimetric analysis showed that increasing S-ChNF content could enhance the intermolecular interaction in the composite system, leading to the formation of a stable network structure, thus improving the rheological properties and enhancing the thermal stability of the composite gel.