Flame retardant polyurethane sponge/MTMS aerogel composites with improved mechanical properties under ambient pressure drying

Considering the low thermal stability and high flammability of polyurethane sponge (PUS) and the poor mechanical performance of methyltrimethoxysilane (MTMS) aerogels, their combination for improvement of characteristics was investigated. The density of prepared polyurethane sponge/MTMS aerogel (PUSMA) composites increased exponentially between 0.032 and 0.13 g/cm3 with the MTMS aerogel content rising, and the thermal conductivity increased linearly between 36.5 and 44.3 mW/(m K). The good hydrophobicity was maintained with a contact angle up to 145.0°. Despite the combination being physical effects, the PUSMA composite presented improved mechanical properties with better integrality and increased elastic modulus. Thermogravimetric analyses suggested that the synergistic effect in the combination improved the thermal stability. The flame combustion probability and the peak heat release rate with flame combustion decreased significantly, implying enhanced flame retardancy of the PUSMA composite. This study from the perspective of composites provides new insight into the development of new high-efficiency aerogel-based thermal insulation materials.