A new type of wood bio-adhesives production: Effect of hydrochar from sewage sludge on adhesives's physicochemical properties

This contribution discloses a new method to prepare formaldehyde-free plywood adhesive using hydrochar after hydrothermal carbonization (HTC) of sewage sludge (SS). Proteins and polysaccharides on the surface of hydrochar can react via cross-linking to form bio-adhesives. The bio-adhesives have an excellent wet shear strength value, meeting the Chinese national standard GB/T 9846-2015 (≥0.7 MPa). During HTC, SS will disrupt the extracellular polymer structure and release organic matter as well as hydrolysis, dehydration, and Maillard reaction occur to develop hydrophobicity in hydrochar. Ash in SS also can play a key role in improving the wet shear strength value of bio-adhesives due to its organic-inorganic hybrid structure. HTC temperature can also significantly influence bonding strength as modifier of the active functional groups in hydrochar. © 2024