Thermally insulating, water-resistant, and fire-safety fully bio-based wheat straw composites

Fully bio-based straw composites have garnered significant attention due to the increasing demand for the disposal of straw waste and the reduction of environmental burdens. However, their application in building and construction remains challenging due to concerns over water resistance, thermal insulation, and fire safety. In this study, we demonstrate the development of wheat straw-based bio-composites through combination of sodium alginate (SA) and phytic acid (PA). SA serves as a binder for the straw, while PA functions as a crosslinker for SA as well as a flame-retardant agent, enhancing both the water resistance and fire safety of resulting composites. The composites show structural integrity after soaking in water for more than 100 h and have thermal conductivity as low as 0.043 W/(m·k). The introduction of PA does not compromise the thermal insulation performance while endows enhanced flame retardancy to the composites, providing self-extinguishing behavior through a synergistic flame-retardant effect in both the gas and condensed phases. This work offers a simple yet effect approach for fabricating thermally insulated, water-stable, and fire-safety fully bio-composites based on straw, holding significant potential for applications in building and construction.