Dual Clay Nanobrick Wall for Heat Shielding and Fire Protection

Heat shielding is a desirable functionality in applications ranging from hypersonic vehicle re-entry to automotive engine and exhaust insulation. Ceramics and metallic alloys can provide effective shielding, but require complex and expensive high temperature as well as significant added weight. Layer-by-layer (LbL) assembled polymer–clay multilayer nanocomposites show great promise as heat shielding alternatives due to their ambient water-based processing, conformal nature, and impressive thermal protection. In this study, a dual clay nanocomposite consisting of polyethylenimine (PEI), tris(hydroxymethyl)aminomethane (Tris), boehmite clay (BMT), and vermiculite clay (VMT) is demonstrated to impart highly effective heat shielding to polystyrene. When compared to the single clay system (PEI-Tris/VMT), the dual clay system (PEI-BMT-Tris/VMT) demonstrates more uniform deposition as well as improved heat shielding capabilities. After a 30 s butane torch exposure (∼1400 °C) the ∼1 μm thick dual clay system on polystyrene has an average after flame and peak temperature of 7 s and 70 °C, respectively, which is significantly improved against the single clay system (after flame ∼ 160 s and peak temperature ∼ 180 °C). The dual clay nanobrick wall provides unprecedented heat shielding capabilities, demonstrating a remarkable step toward cost-effective protection of advanced composite materials.