Preparation and characterization of polymeric cellulose wood adhesive with excellent bonding properties and water resistance

Developing the most abundant cellulose resources in nature as wood adhesives is a challenging but significant work. In this study, an oxidized cellulose-hexamethylene diamine-urea (OCHU) resin adhesive, of high bonding performance, and excellent water resistance has been prepared. The cellulose was firstly enzymatically hydrolyzed to increase its solubility and expose more hydroxyl groups, then oxidized by sodium periodate (NaIO4) to generate a biological compound being rich of aldehyde groups. The OCHU adhesive was prepared by crosslinking oxidized cellulose (OC) with a synthetic reactive polyurea (HU) polymer, which was formed through the deamidation reaction between hexamethylenediamine (H) and urea (U). This adhesive exhibited a 24 h cold water soaking strength of 1.61 MPa, 3 h hot water (63 °C) strength of 1.05 MPa and a dry strength of 1.71 MPa. Compared to oxidized cellulose-hexamethylenediamine (OCH) adhesive, a significant increase of 60 % in this adhesive's wet strength. The Schiff base and addition reactions in the preparation were confirmed by XPS, solid-state NMR, and FTIR. This cellulose-based wood adhesive has great market competitiveness for mass production and application in the plywood industry, due to its excellent bonding properties.