Abstract: In order to improve the flame retardancy of polyurea elastomer (PUA), aluminum hypophosphate (AHP) was used to prepare flame retardant PUA. The thermal performance, flame retardancy, mechanical properties, and flame retardancy mechanism of flame retardant polyurea were systematically studied through a series of tests such as thermogravimetric analysis, ultimate oxygen index, vertical combustion, cone calorimetry, scanning electron microscopy, thermogravimetric infrared spectroscopy, stretching, and tearing. The results indicate that AHP has a high flame retardant efficiency on PUA. At a 20% addition, PUA exhibits self extinguishing properties in vertical combustion tests, and the droplet phenomenon disappears, passing the UL-94 V-0 rating. At the same time, the peak heat release rate, total heat release, total smoke release and other fire safety behavior parameters have significantly decreased. The microstructure and gas phase pyrolysis product analysis of residual carbon indicate that a denser and compact carbon layer is formed on the surface of flame-retardant PUA after combustion, effectively suppressing the generation of hydrocarbons, CO2, CO and other substances in the pyrolysis PUA substrate. The mechanical performance test results show that the addition of AHP has an acceptable loss in tensile strength, elongation at break, and tear strength of PUA. Flame retardant PUA still shows high mechanical properties after 168 hours of thermal oxygen aging treatment.

Key words: polyurea, aluminum hypophosphite, flame retardant, fire safety； thermal oxygen aging