Abstract
Mimosa tenuiflora (Willd.) Poir. (MT) 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. Distilled water, wheat flour, and formaldehyde were also 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, yielded glue lines with similar shear strengths and similar shear deformations if compared to each other. That tannin-based glue incorporated with the tannin extracted using NaOH or NaHSO3 stood out and yielded similar bonding performances if compared to a commercial adhesive applied as a positive control.
Highlights
Located at the semi-arid Brazilian region, the caatinga vegetation has a restricted timber production for several commercial purposes, such as furniture, lumbers, and civil engineering
Raw materials The vegetal sample came from Fazenda Experimental do Núcleo de Pesquisas do Semiárido (NUPEÁRIDO), which belongs to Universidade Federal de Campina Grande (UFCG) and has the geographic coordinates of 07°05′10′′ S and 37°15′43′′ W
The solution generated strong odour gases when heated and the purified Tannin-based liquid extract (LE) demonstrated a decrease in pH after the extraction process
Summary
Located at the semi-arid Brazilian region, the caatinga vegetation has a restricted timber production for several commercial purposes, such as furniture, lumbers, and civil engineering. Most of these available trees have high tortuosities and are overturned before developing high diameters. The concept of sustainability has gained prominence, especially after the Rio-92 Conference. This term can be briefly defined as the ability of humans. According to the Brazilian Institute of Geography and Statistics—IBGE [1], NTFPs have been progressively exploited in Brazil and reached their highest production value in 2018. Açaí berry (R$ 592.0 million), yerba mate (R$ 468.4 million), Brazil nuts (R$ 130.9 million), carnauba wax (R$ 189.2 million), and babassu almonds (R$ 92.1 million) reached outstanding production values in their respective markets [1]
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