Bacterial
cellulose prepared from pellicles of Acetobacter xylinum (Gluconacetobacter xylinus) is a unique
biopolymer in terms of its molecular structure, mechanical strength and chemical stability. The biochemical analysis revealed that various
alkali treatment methods were effective in removing
proteins and
nucleic acids from native membrane resulting in pure
cellulose membrane. The effect of various treatment regimens on thermo-mechanical properties of the material was investigated. The
cellulose in the form of purified
cellulose membranes was characterized by differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA). The glass transition temperature (T(g)) of the native
cellulose (untreated, compressed and dried pellicle) was found to be 13.94 degrees C, in contrast, the chemically treated
cellulose membranes has higher T(g) values, ranging from 41.41 degrees C to 48.82 degrees C. Investigations on isothermal crystallization were carried out to study the bulk crystallization kinetics. Thermal decomposition pattern of the native as well as
alkali treated
cellulose was determined by obtaining thermo-gravimetric curves. At higher temperatures (>300 degrees C), the
biopolymer was found to degrade. Nevertheless, the alkaline treated
cellulose membrane was more stable (between 343.27 degrees C and 370.05 degrees C) in comparison to the native
cellulose (298.07 degrees C). Further, the percentage
weight loss in case of native
cellulose was found to be 26.57%, in comparison to 6.45% for the treated material, at 300 degrees C. The DMTA revealed complex dynamic modulus of the material, at different temperatures and fixed shear stress, applied at a frequency of 5 Hz. The study delineated the effect of
alkali treatment regimens, on the thermo-mechanical properties of bacterial
cellulose for its application over a wide range of temperatures.