THE EFFECT OF CELLULOSE NANOCRYSTALS ON THE PROPERTIES OF ERYTHRINA POEPPIGIANA (Walp.) O.F.Cook PLYWOOD

Abstract

Background: Erythrina poeppigiana is a fast growing, low density tropical wood species underutilized in southern Bahia, Brazil. Its plywood exhibits limited mechanical performance due to wide parenchyma bands, low lignin content, and high porosity. Cellulose nanocrystals (NCC) have been proposed to enhance adhesive bonding and panel stiffness. This study evaluated the effects of incorporating NCC into phenol-formaldehyde adhesive on the physical and mechanical properties of E. poeppigiana plywood.

Results: Five-layer plywood panels were produced with NCC loadings of 0, 1, 1.5, and 2% by mass. NCC addition increased the parallel modulus of elasticity, with 1% sufficient to reach standard requirements for concrete formwork. No significant effect was observed on modulus of rupture. Water absorption and 24-hour thickness swelling increased with NCC, particularly at 1.5% and 2%, reflecting the hydrophilic nature of NCC and the wood’s anatomical structure. Shear strength decreased for NCC contents above 1%, likely due to increased viscosity, hydrogen bonding, and potential NCC aggregation. Other properties, including density and moisture content, remained unaffected.

Conclusion: Low NCC concentrations can improve the stiffness of E. poeppigiana plywood without compromising bonding, whereas higher concentrations negatively affect shear strength and moisture-related properties. The wood’s chemical and anatomical characteristics, notably broad parenchyma bands and low density, influence the overall performance. These findings suggest that controlled NCC incorporation offers a strategy to enhance value-added applications of underutilized species.