Microwave-assisted synthesis of flexible polyimide-modified melamine foam with high flame retardancy

In order to improve the properties of melamine foam (MF), a new polyimide–melamine composite foam (PI–MF) was prepared by microwave irradiation foaming with polyimide microspheres (PI) as a modifier and melamine resin as matrix. The micromorphology, temperature resistance, flame retardant and smoke suppression properties and mechanical properties of the foam were characterized and tested. It was observed by SEM that PI microspheres were closely connected to the skeleton of the MF, FT-IR characterization proved the existence of polyimide in the PI–MF. When the amount of PI microspheres is 30%, the overall performance of PI–MF is better. The temperature of 5% weight loss (T_5%) is 326.02°C, the limit oxygen index is 35.48%, the maximum smoke density is 9.21%, the smoke density rank is 5.43, the formaldehyde content is 46.65 mg kg⁻¹, and the elongation at break of the foam is 35.89%. The introduction of PI microspheres has a good effect on the modification of the thermal stability, flame retardant and smoke suppression properties, and mechanical properties of the MF, and has broadened the application range of polyimide. It also provides a new method for the modification of MF.