Modified basalt/hydrogel composite coating study on the influence of flame retardancy of wood

BS-PA-Al, BS-PA-Ni and BS-PA-Zn hydrogel flame retardant coating materials were prepared respectively using polyvinyl alcohol (PVA)/chitosan (CS) including aluminum hypophosphite (AHP) as hydrogel matrix, and employing basalt (BS) after NaOH pretreatment, KH550 grafting modification and phytic acid co-precipitation act as flame retardant filler. The effects of modified basalt/hydrogel composite coating on flame retarding and mechanical properties of wood were analyzed by thermogravimetric test, cone calorimetric test and vertical combustion test after coating on wood surface respectively. The results show that, due to the dilution of combustible gas and the increase of carbon layer density, the flame retardant properties of BS-PA-Al, BS-PA-Ni and BS-PA-Zn hydrogel flame retardant coated wood have been significantly improved. Among them, the flame retardant properties and mechanical properties of BS-PA-Ni have reached the best, and its UL-94 test has reached V-0 level. The residual carbon rate increased to 27.3%, while the pHRR, THR and TSP decreased by 64.2%, 32.7% and 51.3%, respectively. In addition, when the thickness of the coating is 300 μm, the mechanical properties (tensile strength) of BS-PA-Ni enhanced to 80.4%, and the adhesion strength of the hydrogel on the wood reaches 3.4 MPa.