Influence of Extraction Conditions on Chemical Composition and Thermal Properties of Chestnut Wood Extracts as Tannin Feedstock

Abstract

In view of their use as source material for new biobased flame retardants, chestnut wood extracts were prepared using different solvent systems and compared to an industrial extract. The prepared extracts were mainly composed of hydrolyzed products of ellagitannins (castalin, vescalin, and ellagic acid) along with saccharides. The proportions of components strongly depended on the solvent system used for the extraction. Water-based solvents promoted the recovery of ellagitannins (up to 15 wt % of dry raw matter), while the alcohol-based solvents extracted more selectively ellagic acid (up to 47 wt % of dry raw matter). The phenolic composition of the industrial chestnut wood extract completely differed from that of the lab-scale extracts. The industrial extract was mainly composed of gallic acid and nonhydrolyzed forms of ellagitannins (castalagin and vescalagin). Thermal and fire tests performed on chestnut wood extracts showed high char contents and low total heat release, varying from 33.2% to 38.8% and from 1.1 kJ/g to 6.9 kJ/g, respectively. The values mainly depended on the saccharides, ellagitannins, and ellagic acid contents of the chestnut wood extracts. These results highlighted the promising potential of chestnut wood extracts as biosourced FRs.