New dispersible and low-melting cellulose ester produced with molten adipic acid as a solvent, reagent and catalyst, and its application to improve the mechanical properties of PLA†

Abstract

The synthesis of a new cellulose ester (CE) from microcrystalline cellulose (MCC) and adipic acid is described. The solvent-free reaction was carried at 155 °C, slightly above the melting point of adipic acid. The molten acid is both the reactant and the Brønsted acid catalyst in this reaction. Cellulose adipate is highly crystalline and the modification of the XRD powder pattern with respect to MCC indicates that the spatial arrangement of the pristine cellulose Iβ and its hydrogen bonding network have drastically changed. According to TGA and XRD, esterified cellulose surrounds a core of intact MCC (25% by weight), however, the new cellulose adipate material has a melting point of 153 °C and is dispersable in chlorinated solvents. The composites with PLA were prepared by the solvent casting method. The best results were obtained using 3 wt% of the cellulose ester, with a maximum elongation increased by 59%, and a reduction of the tensile strength of 25% only. The SEM images of the best PLA composite show the absence of the cracks found in the PLA films. This work demonstrates how value-added materials can be prepared from renewable and readily available resources through green and sustainable technologies.