Ionic Liquid Processing of Residual Wood Powder into Additive-Free Wood Composites

This work presents a novel process for production of additive-free wood composites by ionic liquid treatment of wood powder involving extraction of lignin followed by precipitation onto particle surfaces, and hot pressing to form a cellulose-reinforced lignin biocomposite. Physicochemical properties of lignin-coated wood powders, as well as their degree of fusion upon hot pressing, were evaluated with the aim of optimising ionic liquid treatment and hot-pressing conditions. Optimal conditions to achieve complete fusion while minimising process energy demand were determined using response surface methodology, and mechanisms of process parameter effects investigated using gas pycnometry, electron microscopy, image analysis, thermogravimetry, and calorimetry. These novel materials, derived solely from waste with only reusable reagents, represent a sustainable alternative to existing engineered wood products, which rely on petrochemical additives that release toxic volatile compounds, offering a means to reduce environmental and health hazards associated with production and use of composites from wood waste.