Facile and green preparation of carbonaceous material-based wood bio-adhesives using hydrochar from hydrothermal carbonization of glucose with or without acrylic acid/acrylamide

To address the issues of formaldehyde emission, mildew, and easy combustion of traditional wood adhesives, this paper, for the first time, reported formaldehyde-free plywood bio-adhesives using carbonaceous material (hydrochar) generated from hydrothermal carbonization (HTC) of glucose with or without acrylic acid (AA) and acrylamide (AM). The highest wet shear strength of bio-adhesives (BD-G/AA-180) was 1.32 MPa, which meets the Chinese national standard GB/T 9846-2015 (≥0.7 MPa). It was found that functional groups (–NH₂ and –COOH) were abundant on the surface of hydrochar from co-HTC of glucose with AM or AA. The formation of covalent bonds (between components of bio-adhesives; between bio-adhesives and wood) via dehydration or esterification reaction was a key factor in improving wet shear strength during hot-press treatment. Unlike bio-adhesives developed from polysaccharides and proteins, these hydrochar carbonaceous material-derived bio-adhesives had excellent anti-mildew properties and flame resistance with help from ammonium polyphosphate. This work paves a new road to prepare green formaldehyde-free plywood bio-adhesives.