Preparation and analysis of environment-friendly and high- performance cellulose-based wood adhesive

Conventional wood adhesives such as urea-formaldehyde (UF) resin, phenol-formaldehyde (PF) resin, melamine-formaldehyde (MF) resin, and melamine-urea-formaldehyde (MUF) resin have usually problems in formaldehyde emission and derived from petrochemical products, so developing green and environmentally friendly biomass-based wood adhesives has become a research topic of wide focus. As a biomaterial, cellulose (and its derivatives) is the largest bio-resource in the world, and developing its application in wood adhesives synthesis has outstanding raw material advantage. Therefore, in this study, a formaldehyde-free cellulose-based wood adhesive (OCHU) was prepared from carboxymethyl cellulose (CMC) by oxidizing with NaIO₄ and then cross-linked with a laboratory synthetic polyurea compound (HU). The effect of oxidation time, oxidation temperature, NaIO_4, and HU addition on the structures and properties of OCHU adhesive was investigated. The results showed that the adhesive OCHU prepared in 20 % (w/w based on CMC) of NaIO₄ oxidized CMC at 50 °C for 8 h, and then polymerized with HU of equal mass to CMC presents excellent bonding performance. The dry strength, 24 h cold water and 3 h hot water (63 °C) soaking wet strength of its bonded plywood are as high as 1.98 MPa, 1.18 MPa, and 1.40 MPa, respectively, which conformed to the standard requirements in Chinese national standard GB/T 17657-2013. This work provides an effective scheme for preparing cellulose-based wood adhesives with high bonding strength, water resistance, and environmental friendliness. Thus this prepared OCHU adhesive has broad industrial application potential in preparing high-performance plywood.