Chitosan, sisal cellulose, and biocomposite chitosan/sisal cellulose films prepared from thiourea/NaOH aqueous solution

Environmentally friendly biocomposites were successfully prepared by dissolving chitosan and cellulose in a NaOH/thiourea solvent with subsequent heating and film casting. Under the considered conditions, NaOH/thiourea led to chain depolymerization of both biopolymers without a dramatic loss of film forming capacities. Compatibility of both biopolymers in the biocomposite was firstly assessed through scanning electron microscopy, revealing an intermediate organization between cellulose fiber network and smoothness of pure chitosan. DSC analyses led to exothermic peaks close to 285 and 315 °C for the biocomposite, compared to the exothermic peaks of chitosan (275 °C) and cellulose (265 and 305 °C), suggesting interactions between chitosan and cellulose. Contact angle analyses pointed out the deformation that can occur at the surface due to the high affinity of these materials with water. T2 NMR relaxometry behavior of biocomposites appeared to be dominated by chitosan. Other properties of films, as crystallinity, water sorption isotherms, among others, are also discussed.