Multifunctional Lightweight Guanidine Phosphate/Poly(Vinyl Alcohol) Melamine-Based Hybrid Foam for Superior Thermal Insulation and Flame Retardancy

In the field of building energy conservation, advanced thermal insulation materials with low thermal conductivity and excellent flame retardancy have always been a research emphasis. This work proposes a facile strategy for fabricating a hybrid foam based on the skeleton of melamine-formaldehyde (MF) foam, and the GP/poly(vinyl alcohol) (PVA) tightly adheres to the skeleton with the capillary force of MF. The combination of guanidine phosphate (GP) and PVA provides outstanding thermal insulation performance and infrared stealth property to the hybrid foam, and the existence of GP endows the hybrid foam with superior flame retardancy and charring ability. The tensile and compression strength of the GP/PVA@MF hybrid foams have significantly improved. The 1.5 wt % GP/10 wt % PVA@MF (MF-1.5) foam has an ultra-low thermal conductivity value of 0.0293 W m–1 K–1 due to the rational three-dimensional (3D) pore microstructure. Meanwhile, the MF-1.5 foam achieves a V-0 rating in the vertical burning (UL-94) test and a limiting oxygen index of 32.4%. Furthermore, the cone calorimeter results show that the addition of GP significantly reduces total heat release and total smoke release. The GP/PVA@MF hybrid foam will be a multifunctional material with outstanding thermal insulation and flame retardancy, showing a great application in the military and civilian fields.