Thermoplastic translucent film from wood and fatty acids by solvent free esterification: Influence of fatty acid chain length

Transforming wood into thermoplastic material has long been a challenging research topic, nevertheless the application of this technology to the industrial level hampered because of the complex method available. Here, we demonstrate a promising method converting spruce sawdust into thermoplastic material by esterification with various fatty acids of different chain length (4–18 carbon). The esterification was carried out using trifluoroacetic anhydride (TFAA) as a promoter. Weight percentage gain (WPG) of 70% was obtained for the shortest fatty acid used in this study (C4) and increased with the length of fatty acid chain to 271.3% (C18) and ester content were uniformly achieved ranged between 9.10 and 11.27 mmol/gram of wood. Chemical analysis by FTIR and CP/MAS 13C NMR revealed hydroxyl group of esterified wood was replaced by the ester group and alkyl chain. XRD analysis showed decrystallization of cellulose in esterified spruce sawdust. Esterified wood exhibit higher thermal stability observed by TGA and DSC, and presented several softening temperatures observed by TMA. Thermoplastic, translucent, and flexible film were obtained after hot pressing. In contrast with previous research, our study revealed that thermoplastic wood sheet could be obtained by esterification without solvent and at room temperature after only 4 h of reaction.