Sustainable composite material based on surface-modified rape straw and environment-friendly adhesive

[Display omitted] •A material based on rape straw and environment-friendly adhesive was designed.•Bone glue with sodium lignosulfonate was used as a binder.•Rape straw particles were modified using water and sodium hydroxide treatment.•The surface treatment improved the interface adhesion between straw and bone glue.•The best mechanical properties achieved composites with rape straw treated by water. An energy efficient and sustainable composite building material based on rape straw and environment-friendly adhesive is designed. Bone glue with sodium lignosulfonate is used as the binder. Rape straw particles are modified using water and sodium hydroxide treatment. A wide range of functional properties is analyzed, and a detailed characterization of microstructure is performed. The experimental results show that the surface treatment by both water and sodium hydroxide improves the interface adhesion between rape straw and bone glue. The primary consequence is then an increase of both bulk- and matrix density, as compared with the reference material. The best mechanical properties are achieved for the water-treated samples. The sodium hydroxide treatment is found to influence negatively sorption isotherms and to cause greater swelling in a comparison with other composites. The effect of straw surface treatment on thermal and water vapor diffusion properties is not evidenced. The significant swelling of all designed composites at the relative humidities higher than 75% limits their practical applications. They are supposed to be used in dry environments, typically for cladding and insulation in construction, or for packaging purposes.