Effect of down-stream processing parameters on the mechanical properties of bacterial cellulose

Abstract

Bacterial cellulose (BC), a biodegradable polymer with high degree of crystallinity, produced by Gluconacetobacter xylinus, was used as reinforcement in biocomposites. The downstream process parameters involved in the preparation process of BC have important influence on its mechanical properties. The effect of some key processing parameters such as treatment temperature, drying stages, type of treatment solvent and pressure on biocellulose sheets was investigated during drying in order to modify the parameters responsible in mechanical properties. The rise in treatment temperature and drying processes of BC sheets showed about 8 and 11 % reduction in tensile strength, respectively. The addition of NaOH solutions during the treatment reduced the tensile strength of BC sheets sharply, though an increase in NaOH concentration produced treated samples with higher tensile modulus. The use of optimum NaClO solution as a cheap treatment solvent led to an increase of about 10–11 % in the mechanical properties of BC. A pressure increase during drying stage improved the tensile strength of biocellulose sheets by 7 % and resulted in highly enhanced tensile modulus of BC samples. The production process (microbial fermentation) and structural features (porous web-shaped structure) provide an ideal scenario for synthesis of BC composites. A number of schemes have been introduced to synthesize BC composites with different materials. Among these schemes, the initial addition of materials to BC culture media, the treatment of BC with solutions and suspensions, and the dissolution of BC in solvents are the most commonly used techniques.