A strong, flame-retardant, and thermally insulating wood laminate

Developing a strong, flame resistant, and thermally insulating structural material is essential for reducing energy consumption and improving safety in buildings. Wood is a pervasive structural material with natural thermally insulating properties. However, its flammability and insufficient mechanical strength compromises its safety, particularly in mid-rise and high-rise buildings that have higher safety and structural requirements. Herein, we demonstrate a strong, flame-retardant, and thermally insulating wood laminate featuring a compact structure that we synthesized by infiltrating delignified basswood with bentonite nanosheets, followed by hot-pressing to densify the material. Bentonite nanosheets can be infiltrated into the microchannel of the delignified wood to achieve a good compatible and 3D flame resistant protective surface. Flame retardant tests show that the peak heat release rate of this wood laminate is reduced by more than 50% compared to natural basswood. Additionally, the wood laminate does not start to burn until after 7 min of direct exposure to an open flame, and then self-extinguishing when removed from the igniting flame, suggesting the excellent flame resistance of the composite. The wood laminate also exhibits a high tensile strength of 330 MPa that is more than 8-times higher than the starting material. In addition, the wood laminate exhibits lower thermal conductivities of 0.2 and 0.18 W m−1 K−1 in the axial and radial direction, respectively. The demonstrated wood laminate shows great promise as a high-performance structural material with strong flame-retardant, thermally insulating, and mechanical robust properties that are needed for the construction of energy efficient buildings.