Highly dispersed red phosphorus produced by mechanical milling for enhanced flame retardancy of polyurethane-based foam

To improve the exothermic temperature and flammability of polyurethane foam (PUF), red phosphorus (RP) and diatomite (D) from mechanical milling were chosen as the flame retardants to be incorporated into the polyurethane/waterglass foam (PUHF). The maximum exothermic temperature and temperature distribution of PUF and PUHF were measured using an infrared thermal camera. The morphology and chemical structure of the flame retardants as well as the chemical structure, morphology, compressive strength, thermal stability and flame retardancy of different PUFs were comprehensively investigated by scanning electron microscope, energy dispersive spectrometer, Fourier transform infrared spectroscopy, X-ray diffraction, compression test, thermogravimetric analysis, limiting oxygen index, vertical burning combustion test, cone calorimetry and X-ray photoelectron spectroscopy. The obtained results showed that the maximum exothermic temperature and temperature distribution of PUHF were lower and more uniform than those of PUF. The addition of D increased the dispersion of RP in PUHF, and the uniform and closed pore structures and compressive property were well-retained. Moreover, RP/D/PUHF exhibited excellent thermal stability and flame retardant properties. In addition, a possible flame retardant mechanism of RP/D/PUHF was proposed.