Tannin-Based Extracts of Mimosa Tenuiflora Bark: Features and Prospecting as Wood Adhesives

Abstract

Mimosa tenuiflora (Willd.) (MT) Poir. is an underutilized plant specie since its wood is mostly used for energy production. Nonetheless, the bark from this forest plant has a high amount of tannins and other valuable compounds. Tannins have high worldwide importance and, because of that, there is an increasing number of researches on biorefinery systems aiming at maximizing their exploitation. The present study evaluated tannins extracted from the MT bark and their use for producing wood adhesives. Three types of powdered tannins were extracted using different solvents: a pure aqueous solution, a 5% sodium hydroxide (NaOH) aqueous solution, and a 5% sodium bisulfite (NaHSO3) aqueous solution. Also, distilled water, wheat flour, and formaldehyde were used as a solvent, a glue extender, and a catalyst, respectively. These adhesives were applied for bonding pine wood joints and their shear strengths were determined. All the MT-based adhesives showed high viscosities and, if compared to each other, yielded glue lines with similar shear strengths and similar shear deformations. That tannin-based glue incorporated with the tannin extracted using NaOH/NaHSO3 stood out and yielded a similar bonding performance compared to a commercial adhesive applied as a positive control.

Effect of the pH value of tannin extracts on properties of classic tannin foams

“…5 Condensed tannins are important raw materials for many eco-friendly products, including tanned leather and wood adhesives. 6 They are rich in phenolic and aliphatic hydroxyl groups, 1 which are responsible for many of their remarkable features, such as metal-chelating, antioxidant, and fire-resistant properties. 7,8 The latter characteristic is aligned to current concerns on conflagrations and, for this reason, different tannin-based insulating materials (such as tannin foams and polymer foams reinforced with tannin particles) have been investigated aiming at avoiding fire accidents.…”