Properties of cross-laminated timber bonded with an adhesive based on tannins from the bark of Mimosa tenuiflora trees

Abstract

This study aimed to determine the concentration of condensed tannins in the bark of Mimosa tenuiflora (Willd) Poir trees. Additionally, the physical-mechanical properties of cross-laminated timber (CLT) panels bonded with an adhesive based on M. tenuiflora tannins were assessed. Bark was collected from five trees. The adhesive formulation was synthesized by mixing powdered tannins, paraformaldehyde, and water at 50 °C under continuous stirring. Bark tannins extract in its pristine state without any previous chemical treatment or modification was employed to synthesize the adhesive. Viscosity, pH, solids content, and gel time of the adhesive formulation were determined. CLT panels were manufactured with Eucalyptus spp. wood. The bonding performance was assessed by determining the physical (apparent density and water absorption) and mechanical (modulus of elasticity – MOE, modulus of rupture – MOR, and shear strength) properties of the CLT panels. Condensed tannins content in the M. tenuiflora bark was 23.4%. Adhesive properties were pH = 3.93, TS of 50.64%, gel time of 460 s, and 6,000 cP for viscosity. Values of MOE, MOR and shear strength were 4,411, 16.18, and 1.06 MPa, respectively. The M. tenuiflora tannins are promising for the formulation of adhesives to bond CLT.