Nanohybrids of nano-silica and cellulose linters: thermal stability, rheology, and gelation kinetics

In this research, hybrids (NH-CMC-nSiO₂) were synthesized using a carbodiimide-mediated amidation reaction from carboxymethylcellulose (CMC) obtained from cellulose extracted from cotton linters and amino-functionalized silica nanoparticles (nSiO₂-APTES). One of the nanoparticles was obtained commercially (nSiO₂-2% APTES), while the others required the corresponding amino-functionalization reaction with the respective aminosilane (APTES). The precursors and products were characterized by spectroscopic (FTIR-ATR, DLS, Pζ, XRD, XPS, SEM, EDS) and thermogravimetric (TGA and DSC) techniques. Additionally, the viscosifying and gelation capacity of NH-CMC-nSiO₂ solutions and its precursor biopolymer solutions were evaluated under different temperature and salinity conditions. The results reveal that the hybrid materials show similar thermal properties, but differ in morphology, chemical structure, and crystallinity properties compared to CMC’s. Subsequently, a viscosity study was performed on the new obtained hybrid materials; the viscosities of the hybrids increased significantly compared to carboxymethylcellulose, with a viscosity difference of 9 cP for NH-CMC A380-APTES. Finally, the gelation kinetics and thermal stability of the gels at different concentrations of the new nanomaterials and cross-linker were evaluated, validating that these materials are suitable for being incorporated into chemical conformance treatments.