Glueless formaldehyde-free biocomposites with high strength based on the three-dimensional structure of wood fibres

Abstract

The efficient utilization of small-diameter shrub resources holds significant potential in averting forest resource waste and mitigating carbon emissions. Herein, glueless biocomposites were prepared using waste small-diameter Buxus megistophylla via alkali pre-treatment and thermal molding. Instead of simple hot-pressing, the biocomposites were prepared using thermal molding, which allows the release of edge stresses in a high-pressure environment. After alkali pretreatment, the flexural and tensile strength of the biocomposites increased by 66.08% and 74.12%. Alkali pre-treatment forms reactive alkali-cellulose, facilitating fiber bonding. Structural disruption leads to fiber swelling, increasing surface area and hydrogen bonding, especially on cellulose. This process disrupts and reconstitutes crystalline regions, enhancing crystallinity. Lignin liberated from the lignin-hemicellulose polymer transitions to a molten state, serving as an adhesive to fortify fiber bonds, creating a 3D lattice structure and hydrophobic surface (Water contact angle 85°). Furthermore, these biocomposites, being adhesive-free and non-emitters of harmful gases like formaldehyde, hold promise as sustainable materials for architectural decoration and furniture applications.