Composite materials based on modified lignosulfonates and cellulose-containing waste

Introduction. Waste from wood processing and agricultural products can be used as components of building materials, as fuel in briquettes, etc. A rapidly developing area for the utilization of this waste, as well as waste from the pulp and paper industry, is its use as a resource for producing building materials. The aim of the research is to study the possibility of using waste from wood processing and paper production, including lignosulfonates, as binders for the creation of composite materials. Methods and Materials. The object of the study is a heat-insulating material based on wood processing waste and a modified lignin-containing binder, as well as methods for modifying this binder. The possibility of using sodium lignosulfonate activated with an aqueous solution of boron-nitrogen compounds was studied as a binder. The samples were produced by pressing softwood sawdust with modified lignin, followed by heat treatment of the molded green product. Results. The values of density and strength of the samples were determined depending on the composition and heat treatment regimes. It was found that the samples with modified lignosulfonate exhibit the best properties. Digital optimization of the manufacturing parameters and formulation factors was carried out for this material. It was established that the best properties are achieved with an average softwood sawdust size of 8.0 mm, a modifier content of 7.5%, and a heat treatment temperature of 103–104 °C. The flexural strength of the samples with the optimal composition is 3.4–3.5 MPa, the compressive strength at 10% deformation is 4.7 MPa, and the average density is 683 kg/m3. The discrepancy between the calculated and experimental values for flexural strength does not exceed 7.0%. Discussion. The experiments, including those conducted using digital methods, confirmed the feasibility of using boron-nitrogen compounds to modify the properties of lignin, which can be considered as a natural binder. Conclusion. The obtained products fully comply with the requirements for composite heat-insulating materials, and the use of boron-nitrogen compounds as a modifier not only affects the mechanical properties of the products but also increases the resistance of the resulting material to decay processes and other biological impacts.