Bacterial cellulose/silica nanocomposites: preparation and characterization.

The preparation and characterization of bacterial cellulose (BC)/silica nanocomposites are presented in this paper. BC hydro-gel was immersed in an aqueous solution of tetraethoxysilane (TEOS). By pressing the treated BC matrices at 120 °C and 2 MPa, water-free translucent sheets were obtained. TEOS concentration (3, 5 and 7%) and press time (8, 10 and 12 min) were used as variable factors. These materials were characterized by different techniques, namely FE-SEM, FTIR, SEM, tensile strength and Young's modulus. All composites showed good dispersion of the fibers and strong adhesion between the fibers and the matrix. FE-SEM observations showed that the nano-scale silica was embedded between the voids and micro-fibrils of the BC matrix. Reflecting this structure, the maximum Young's modulus and tensile strength of dry BC/silica composites improved to 1.46 GPa and 113 MPa, respectively. The tensile strength and Young's modulus showed 35 and 18-fold increase (with 7% TEOS), respectively, while the same properties were reduced 15 and 10-fold with increase in press time from 8 to 12 min. FTIR results illustrated strong chemical interactions between the cellulose and silica phases. The optimum condition was obtained when the TEOS dosage and press time were 7% and 8 min, respectively.