Study on the hydrophobic nano silica particles as flow-enhancing additives for ultrafine dry powder fire extinguishing agent

Sodium bicarbonate-based ultrafine dry powder fire extinguishing agents (UDEAs) exhibit high hygroscopicity and a tendency to agglomerate, which result in poor flowability and diminished extinguishing efficiency, thus proving to be crucial concerns in the UDEA design. The integration of hydrophobic nano silica (HNS) has been recognized as an effective strategy to tackle these challenges, but the precise optimal quantity of HNS in UDEA has been a subject of confusion. Consequently, the impact of HNS as an additive on the flowability of sodium bicarbonate UDEA was thoroughly examined. Through high-speed stirring, the surface of UDEA was evenly coated with HNS particles, resulting in a notable increase in the contact angle of the modified extinguishing agent to approximately 135.4°. Notably, the UDEA formulation with an 8% HNS addition exhibited the least cohesion, the highest flow function value, and the lowest spray resistance. Moreover, the study unveiled the underlying flow mechanism of sodium bicarbonate UDEA influenced by the HNS additive. The findings indicated that the most effective incorporation of HNS into sodium bicarbonate UDEA was 8%, considering both its hydrophobic properties and flow characteristics.