Multi-functional flame retardant coatings comprising chitosan/ gelatin and sodium phytate for rigid polyurethane foams

In this work, a renewable multi-functional composite was fabricated from the combination of chitosan, gelatin and sodium phytate by a simple and eco-friendly process. The obtained products were analyzed by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, scanning electron microscopy and X-ray photoelectron spectrometry. The above composites were then added onto the surface of rigid polyurethane foams by a rolling procedure. The flame performance test conducted by cone calorimeter demonstrated that the surface coating could effectively reduce the value of peak heat release rate and total heat release to 115.0 kW/m2 and 3.5 MJ/m2 from 247.2 kW/m2 and 6.8 MJ/m2 of the rigid polyurethane foams, respectively. Except for foams, the coating composite also exhibited high flame-retardant efficiency in wood, plastic and fiber. Through mechanism analysis (morphology observation by scanning electron microscopy, structural analysis by X-ray photoelectron spectrometry, Fourier transform infrared spectra and pyrolysis-gas chromatography/mass spectrometry), it was suggested that the coating composite mainly took effect in condensed phase by the formation of physical barriers. Moreover, the newly prepared polyurethane foam composites also exhibited superior organic dye adsorption properties. This work provides an efficient, simple and eco-friendly route for large-scale production of multi-functional renewable materials that can be used in the fields of fire safety and environmental conservation.