Effect of partial delignification and densification on chemical, morphological, and mechanical properties‏ of wood: Structural property evolution

Abstract

Efforts have been dedicated to developing sustainable alternatives for conventional construction materials, resulting in the development of densified wood as an innovative, environmentally friendly, and high-performance material. This study focuses on investigating the effects of treatment parameters (e.g., partial delignification boiling time, chemical concentrations, and hot-pressing pressures) on the chemical, morphological, and mechanical properties of the densified wood. Results revealed that the partial delignification process of low-density Balsa wood reduced lignin content by 50–80%, which enhanced the crystallinity of the wood by 21–54%. However, prolonged periods of partial delignification caused a degradation in the crystalline regions in wood. The modulus of rupture (MOR) and modulus of elasticity (MOE) of the densified wood samples increased by 90–680% and 10–810% compared with those of the raw wood samples, respectively. The MOR of the densified wood also showed a dependency on lignin content and porosity. An optimal lignin content of approximately 10% was associated with the highest MOR in densified wood. Moreover, the relationship between the MOR and porosity suggested that the MOR improvement occurred in two stages. The first stage of MOR improvement is controlled by the reduction in the porosity and the second stage is controlled by the improved hydrogen bonding among cellulose nanofibrils.