Extraction of Polyphenolics from Lignocellulosic Materials and Agricultural Byproducts for the Formulation of Resin for Wood Adhesives

Extractions of polyphenolics were performed from low cost agricultural by-products for the elaboration of adhesive formulations. Lignin was extracted from Miscanthus x Giganteus in 13% yield based on miscanthus dry mass using an ethanol organosolv process (using the following conditions: T = 190 degrees C, t. 60 min, Sulfuric acid = 1.2% w/w, EtOH/H2O = 0.65). Condensed tannins were extracted from grape pomace in an aqueous solution of sodium carbonate and sodium sulfite in 22% yield (based on dry mass). Resin formulations in which the total polyphenolic contents (tannin and/or lignin) are from 70% to 95% of the total resin solids content were tested and employed for the elaboration of particleboards. Mixtures glyoxalated lignin/tannin, pure tannin and mixtures tannins/synthetic resins were produced and tested. The most of the adhesives produced yielded good internal bond strength results of the panels, enough to pass relevant international standard specifications for interior-grade panels (European Norm EN 312).