Biomass cellulose-based wood adhesive with improved water resistance and bonding strength by esterification reaction

Traditional wood adhesives are often fabricated from unsustainable fossil resources. Due to their biodegradability, biomass-based adhesives have attracted a lot of attention. Cellulose, a renewable biomass resource with characteristics of low cost and wide availability, has been considered as a promising candidate for the preparation of wood adhesive. Nevertheless, biomass adhesives present a number of challenges in practical applications, most notably their inherent poor water resistance and relatively low bond strengths. In this work, a cellulose adhesive was prepared by carboxymethyl cellulose (CMC) and citric acid (CA) through an esterification reaction. The esterification reaction between the CMC and CA has been demonstrated. by Fourier Transform Infrared Spectroscopy (FT-IR), X-ray Photoelectron Spectroscopy (XPS) and Liquid Chromatography-Mass Spectrometry (LC-MS), and the structures of the reaction products and by-products were deduced. The parameters of the CA/CMC mass ratio and reaction time were optimized to modify the adhesive. As the mass ratio of CA/CMC increased, the water resistance of the resulting adhesive exhibited a gradual improvement. When the ratio of CMC to CA was 1:1, the temperature of hot-pressing was 200°C, and the reaction time was 1 hour, the prepared adhesive endowed plywood with dry shear strength (1.53 MPa), wet shear strength at 20℃ (1.62 MPa), and wet shear strength at 63℃ (1.78 MPa), which are contented with the stipulation of GB/T 9846–2015 (≥0.7 MPa). The cellulose-based adhesive developed in this work shows considerable potential for supplanting fossil-based wood adhesives.