Effect of Drying Methods on Structure and Mechanical Properties of Bacterial Cellulose Films

Abstract

Bacterial cellulose (BC) gelatinous films prepared in stationary culture were dried by three different drying methods: hot air drying, vacuum drying and vacuum freezing drying. The structure of dried bacterial cellulose films was characterized using scanning electron microscopy (SEM), infrared spectroscopy (IR) and X-ray diffraction (XRD), and mechanical properties were tested. The results showed that the surface of films prepared by hot air drying were uniform and dense, cavities and cracks configurations existed in vacuum dried films, and layer and porous structures were observed in vacuum freezing dried films. FTIR spectra and X-ray pattern confirmed that vacuum freezing drying reduced the strength of hydrogen bonds between cellulose macromolecules and the degree of crystallinity of BC films but had little influence on the crystal structure. For those reasons, mechanical properties of BC films prepared by vacuum freezing drying were lower than that of those films by other methods.