Wood Esterification by Fatty Acids Using Trifluoroacetic Anhydride as an Impelling Agent and Its Application for the Synthesis of a New Bioplastic.

Fatty acids (FA) and their derivatives with long alkyl chain structures are good candidates for wood esterification to confer thermoplastic properties to wood. Nevertheless, they do not react easily with hydroxyl groups of wood. In this study, we investigated the reactivity of wood with various fatty acids of different chain lengths using trifluoroacetic anhydride (TFAA) as the impelling agent in various reaction conditions. Generally, the esterification of fatty acids without solvents resulted in higher Weight Percentage Gain (WPG) and ester content than the reaction in the presence of CH2Cl2. The esterification reaction could be performed effectively at room temperature, though an increased reaction temperature provoked degradation of the esterified wood. WPG of 67% was obtained for the C3 and 253% for the C16 alkyl chain analogs, respectively. Nevertheless, the ester content was fairly uniform, with values between 10.60 and 11.81 mmol ester/gram of wood for all chain lengths. A higher quantity of reagent led to higher ester content, which tended to stabilize after a ratio of 1:4 wood and TFAA/FA. The esterification reaction was performed rapidly, with an ester content between 7.65 and 9.94 mmol ester/gram of wood being achieved only after 15 min of reaction. Fourier transform infrared spectroscopy (FTIR) analysis was performed to confirm the drastic chemical changes of wood before and after esterification. Morphological observation by scanning electron microscope (SEM), softening measurement by thermomechanical analysis (TMA), and contact angle measurements demonstrated the possibility of esterified spruce wood being applied as a new bioplastic.

Fully wood based novel translucent and thermoplastic materials by solvent-free esterification.

Wood has been investigated for bioplastic production because of its abundance and biorenewability to reduce dependence on petro-based plastics. A series of experiments have been carried out to graft myristic acid, chosen as the fatty acid model, onto spruce sawdust using trifluoroacetic anhydride (TFAA) as the impelling agent without any solvent. The reaction was performed rapidly, leading to high ester content. Most of the hydroxyl groups in wood structure reacted with myristic acid, as demonstrated by FTIR and CPMAS 13C NMR. XRD measurements indicated a decrease in wood crystallinity. Myristic acid-esterified wood showed higher thermal stability by TGA and DSC and delivered several softening temperatures, as observed by TMA. Thermoplastic and translucent films were obtained after pressing at a high temperature. Scanning electron micrographs revealed that pressed esterified wood at the high temperature showed complete disappearance of fibrous structure to a smooth and homogenous surface, indicating that thermal fluidity was achieved during pressing. Esterified sawdust film also showed surface hydrophobicity by contact angle measurements.