Fabrication of carbon black coated flexible polyurethane foam for significantly improved fire safety

Fire resistant coatings, composed of nanosized carbon black (CB) and polyurethane acrylate (PUA), were synthesized through a facile and low-cost method to improve the fire safety and thermal stability of flexible polyurethane foam (FPU). Scanning electron microscopy and total reflection Fourier transform infrared analysis results demonstrated the successful deposition of the coating on the surface of FPU foam and the morphology change of FPU with different concentrations of CB. Thermogravimetric analysis results revealed that the thermal stability of the coated FPU foams was significantly improved. The char residue of FPU/CB 8% was increased to 28.4% from 4.0 wt% of pure FPU. The coated FPU foam with a CB concentration of 8 wt% exhibited a great reduction of 80% in peak heat release rate (pHRR), attributing to the physical barrier effect of the CB filled coating. The observation of the char residue indicated that FPU/CB 4% exhibited the best shape char residue without collapse and cracking. Simultaneously, the SEM images of the char residues of the coated FPU foams showed that carbon black based coating promoted the generation of a compact char layer, suggesting a good physical blocking effect. Raman spectroscopy also confirmed that the graphitization degree of char residue FPU/CB 4% was the lowest, with the more stable structure. The coated FPU foam also has a certain inhibitory effect on the smoke release.