No abstract

The method of manufacturing nanosized spherical superhydrophobic silica particles is reported. The efficiency of hydrophobized nanosilica (NS) as an additive to fire extinguishing powders (FEP) based on ammonium phosphates was evaluated. The effect of hydrophobization on the texture properties, size, and shape of the NS additive particles was studied. The surface of the fire extinguishing component is uniformly coated by spherical hydrophobized NS nanoparticles without a high-speed mixing procedure. NS additive provides a highly hydrophobic coating to the particles of the FEP + NS fire extinguishing powder. The apparent contact angle of the coated particles was found to be larger than 160°. The dynamic flow resistance of commercial and FEP + NS fire extinguishing powders was compared. The specific energy and aerated flow energy of the FEP + NS is relatively low, thus indicating a weak aerodynamic interaction between the particles in dynamic processes. It was established that the spraying resistance of FEP + NS is the lowest among the studied fire extinguishing powders (including commercial ones), so it is characterized by the best flowability.

Textural and morphological features of hydrophobic silicon dioxide, obtained by the hydrolysis of tetraethoxysilane in an ammonia medium followed by modification of a spherical SiO2 particles surface with a hydrophobic polymethylhydrosiloxane, were studied in this work. The size of silicon dioxide particles was controlled during preparation based on the Stöber process by variation of the amount of water (mol) in relation to other components. The ratio of components, synthesis time and amount of the hydrophobizing agent were determined to obtain superhydrophobic monodisperse silicon dioxide with a spherical particle size of 50–400 nm and a contact angle of more than 150°. In the case of the struvite example, it was demonstrated that the application of spherical- shaped hydrophobic silicon dioxide particles in powder compounds significantly improves the flowability of crystalline hydrates. The functional additive based on the developed silicon dioxide particles makes it possible to implement the use of crystalline hydrates in fire-extinguishing powders, preventing agglomeration and caking processes. The high fire-extinguishing efficiency of the powder composition based on struvite and the developed functional additive has been proven by using thermal analysis methods (TGA/DSC).