Spray atomization-assisted pulsed-CVD surface coating for flame-retardant polyurethane foam

Polymeric thermal insulation materials, especially polyurethane foams (PUF), are widely used in buildings to diminish the energy penalty but highly flammable. To reduce the flammability and smoke release of polyurethane foams without sacrificing the inherent properties, we report an efficient strategy involving pulsed chemical vapor deposition (Pulsed-CVD) and spray atomization to generate a phosphorous/SiO₂ nanolayer with a thickness below 200 nm on polydopamine modified rigid polyurethane foams. Due to the unique multilayers structure, the resultant composites showed an extra-ordinary thermal conductivity of 31.9 mW m⁻¹ K⁻¹ and enhanced compressive strength of 42%. Notably, the surface-treated PUF was hard to ignite in vertical test and had a very high limited oxygen index (LOI) value of 34.3%. Cone calorimetry (CC) results revealed that the total heat release (THR) and the total smoke release (TSR) were reduced by 32.9% and 64.3%, respectively. And the close-cell char structure was perfectly retained after CC test. The mechanism research suggested that silica and phosphorus promoted char formation, limited heat release and thermal degradation during combustion. These results indicate the strategy with a mild process has potential for industrialization with superior fire safety and structure stability in polymeric insulation materials.

The polydopamine (PDA)-coated commercial polyurethane foam was treated through the pulsed-CVD and spray atomization strategy, the surface was decorated with flame retardant layers, and the flame and fumes were efficiently suppressed by instant char-forming and dense surface carbon barrier without sacrificing its inherent properties.