PARTIAL REPLACEMENT OF TANNIN WITH NANOLIGNIN FOR THE FORMULATION OF ADHESIVES FOR BONDING PLYWOOD PRODUCED WITH ERYTHRINA POEPPIGIANA WOOD.

Abstract

Background: Fast-growing species are crucial for the wood panel market, and Erythrina poeppigiana(mulungu) emerges as a promising alternative. Although its wood is not suitable for high-performance applications, using its veneers for plywood supports the diversification of raw materials in forestry. Furthermore, replacing petrochemical-based adhesives is essential due to associated health and environmental risks. Tannins from forest species provide a sustainable alternative; however, their mechanical strength and moisture resistance must be improved. Nanolignin, a nanoscale additive, enhances these properties, making it a viable option for biodegradable adhesives. This study evaluates plywood production using E. poeppigiana veneers bonded with a tannin–nanolignin adhesive.
Results: Adhesives were formulated with Acacia mearnsii* tannin partially replaced by nanolignin at different concentrations and tested for rheological properties. The wood, sourced from experimental plantations in Ilhéus, Bahia (Brazil), was processed into five-layer plywood panels bonded with 320 g/m² of natural adhesive and pressed at 150 °C and 1 MPa for 10 minutes. The resulting panels were evaluated for physical and mechanical properties, contact angle, scanning electron microscopy (SEM), acoustic insulation, and thermal conductivity. The results confirmed E. poeppigiana as a viable raw material for plywood production. Partial replacement of tannin with 1–2% nanolignin reduced adhesive viscosity, improving application and veneer penetration. The 2% nanolignin formulation increased hydrophobicity, reducing water absorption, while shear strength tests revealed higher cohesion and adhesion, particularly in adhesives containing 2–3% nanolignin.
Conclusions: The findings demonstrate that E. poeppigiana veneers bonded with tannin–nanolignin adhesives can produce plywood panels with suitable physical and mechanical performance. The incorporation of small amounts of nanolignin enhances the adhesive’s rheological and bonding characteristics, contributing to improved durability and water resistance. These results support the potential use of E. poeppigian and nanolignin-modified tannins as sustainable materials in eco-friendly plywood manufacturing.Keywords: Alternative raw material; Environmentally friendly production; Natural adhesives.