Acetylated, phosphorylated and sulfonated nanocellulose for the modification of urea-formaldehyde adhesive in particleboard production.

The functionalization of nanocellulose (NC) to enhance its effect on UF resin properties and wood-based materials still remains insufficiently explored. NC was modified via acetylation, phosphorylation, and sulfonation. ATR-FTIR analysis combined with quantitative methods, including acid-base titration, potentiometric titration, and elemental analysis, confirmed successful NC functionalization. Both unmodified and modified NC affected the properties of urea-formaldehyde (UF) adhesive mixtures. Gel time decreased in adhesives containing acetylated NC, while viscosity increased most in mixtures with phosphorylated and sulfonated NC. Thermogravimetric analysis of UF adhesives containing NC showed improved stability, with phosphorylated NC providing the highest thermal resistance and acetylated NC enhancing stability only at lower temperatures up to 250 °C. Mechanical testing indicated that the incorporation of NC enhanced the strength of the particleboards. Variant containing acetylated NC achieved the highest internal bond and was the only one among functionalized variants to significantly improve bending strength and modulus of elasticity. Dimensional stability was enhanced, with acetylated NC reducing thickness swelling after both short- and long-term water exposure and limiting water absorption after short-term exposure. Phosphorylated and sulfonated NC also reduced thickness swelling, but only during short-term exposure. Overall, acetylation was the most effective modification, enhancing UF adhesive performance and particleboard quality in the most significant way.