Work

Robust and dimensionally stable birch wood laminates with increased relative cellulose content and phenol formaldehyde resin impregnation

Year: 2025

Type: article

Abstract: The beneficial effects of delignification, densification, and resin impregnation on wood properties are well studied. However, only few studies address all aspects mentioned in a single series of experiments, and rather focus on delignification or resin impregnation separately. To close this gap, a comprehensive series of experiments using birch was performed. Laminates from alkaline-extracted veneers were impregnated with phenol formaldehyde (PF) resin in various concentrations and characterized by three-point bending and water immersion tests. For reference, non-extracted specimens were produced and characterized. Several significant effects were observed. Firstly, densification leads to improved mechanical performance, which is more pronounced after extraction of non-cellulosic cell wall components. Secondly, PF-resin impregnation improves mechanical performance for both variants. Once impregnated, further increases in PF-resin concentration improve mechanics for non-extracted specimens, whereas mechanical performance is reduced in extracted variants. Maximum values of bending properties with an elastic modulus of 48 GPa and a bending strength of 470 MPa were observed at 5 % resin concentration in the impregnation solution. As for dimensional stability, PF-resin impregnation significantly reduced the swelling of densified specimens in liquid water. At a PF-resin concentration of 10 % in the impregnation solution, dimensional stability equal to native wood was achieved.

Source: Carbohydrate Polymer Technologies and Applications

DOI: 10.1016/j.carpta.2025.100744