Effect of xanthan gum on the physical and chemical features of microfibrillated cellulose films plasticized by glycerol

Development of biocomposites from polysaccharides is of universal interest due to the possibility of obtaining new polymeric materials of sustainable origin, reducing the use of petroleum-derived molecules and helping to establish a system based on the notion of green economy. This study aimed at evaluating thermal and mechanical characteristics of microfibrillated cellulose (MFC) films incorporated with different xanthan gum (XG) and glycerol contents. In the processing, all components were mechanically homogenized, poured into a Petri dish, and then dried at 60 degrees C for 18 h. The films were evaluated by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), apparent contact angle, thermogravimetry (TG), tensile properties, and X-ray diffraction (XRD). In a comparison between the formulations, the film containing 2.8 g of MFC and 0.5 g of XG showed the highest thermal stability up to 350 degrees C. Despite the hydrophilic character of the studied biopolymers, the physical interactions between these macromolecules yielded hydrophobic surfaces with apparent contact angles up to 128 degrees, especially when the glycerol was not added. The addition of glycerol conferred decreases in transmittance, surface wettability, tensile strength, tensile modulus, and crystallinity index, which were accompanied by increases in apparent density and elongation at break. The XG addition caused an increase in hydrophobicity, in addition to decreases in thermal stability, transmittance, tensile strength, tensile stiffness, and crystallinity index. The high hydrophobicity of the films obtained suggests that the studied materials have potential application in food packaging, hindering the permeation of water.