Layer-by-layer assembly of calixarene modified GO and LDH nanostructures on flame retardancy, smoke suppression, and dye adsorption behavior of flexible polyurethane foams

In this study, the effect of LbL coatings based on layered double hydroxide (LDH), graphene oxide (GO), and sodium p-sulfonatocalix[4]arene (SC4A) modified graphene oxide (GOSC4A) on the fire properties and dye adsorption behavior of flexible polyurethane foam was investigated. For this purpose, samples including neat PU foam and modified PU foams with 3, 6, and 9 bilayers of LDH-GO and LDH-GOSC4A coatings were prepared. SEM micrographs of the prepared foams confirmed the presence of LDH-GO and LDH-GOSC4A coatings on the foam surface and showed that the LDH-GOSC4A layers form a denser and more uniform coating on the PUF surface. Combustion studies of prepared foams using CCT and horizontal burning test demonstrated that at the same number of bilayers, foams including LDH-GOSC4A coatings showed better flame retardancy than LDH-GO coated foams. Therefore, the PUF/LDH-GOSC4A 9BL foam showed the best fire properties, and its PHRR, THR, and TSP values were reduced by 28.8, 11.8, and 36.3%, respectively, compared to uncoated PUF. Methylene blue (MB) adsorption studies revealed that adsorption of MB onto PUF/LDH-GOSC4A 9BL is well consistent with the pseudo-second-order kinetic model and its maximum adsorption capacity is 38.46 mg/g based on the Langmuir isotherm equation.