Enhanced flame-retardant performance of rigid polyurethane foam by using APTES-MMT and ATH mixed intumescent coatings

The design of environment-friendly fireproof rigid polyurethane foams (RPUFs) that completely prevent ignition or the spread of fires is important for energy conservation and emission reductions. In this paper, an intumescent flame-retardant coating was prepared and coated onto the surface of a RPUF to improve its flame retardancy. Vertical combustion experiments (UL-94) showed that, compared with the pure RPUF, a RPUF coated with the expansion coating successfully self-extinguished without a droplet formed after ignitor removal. Thermogravimetric analyses showed that the expanded coating effectively increased the rate of carbon residue formation. Cone calorimetry showed that when the pigment-to-binder ratio was 3.5:1, with 5% modified montmorillonite, 6% aluminum hydroxide, and 4% titanium dioxide, the intumescent coating effectively reduced the heat release rate and total heat release of the RPUF. Remarkably, the smoke release rate and total exhaust gas volume showed that the expanded coating provided obviously enhanced smoke suppression. Therefore, the flame retardancy and toxic smoke suppression provided by the RPUF thermal insulation material is essential and very useful for healthy development of human society and the environment.