Rheology of epoxidized cellulose pulp gel-like dispersions in castor oil: Influence of epoxidation degree and the epoxide chemical structure

Several di- or tri-functional epoxides were used to chemically modify an industrial grade cellulose pulp from Eucalyptus globulus in order to thicken castor oil by dispersing epoxidized cellulose pulp fibers, resulting gel-like formulations with potential applications as biolubricants. Rheological properties of these colloidal suspensions were evaluated by analysing the effects of epoxidation degree and the epoxide chemical structure. With this aim, epoxidized cellulose pulp samples were characterized by means of epoxy index determination, thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. It was found that linear viscoelastic functions, determined in small-amplitude oscillatory shear (SAOS), and viscosity values of epoxidized cellulose pulp gel-like dispersions decreased by increasing the epoxy index, whereas the shear-thinning character was dampened with the extension of epoxidation. Aromatic di-functional epoxides provide higher values of these rheological functions than aliphatic ones.