Experimental Study On Combustion And Explosion Characteristics Of Hydrophobic Silica Aerogel

Hydrophobic silica aerogel is an important energy-saving and thermal insulation material.In recent years,it has gradually become the preferred material to achieve the goal of carbon neutralization,and has a broad application prospect.Due to the presence of surface organic functional groups in hydrophobic silica aerogels,there are still risks of combustion and dust explosion in specific environments（such as high-temperature fire and high-pressure oxygen）,so it is necessary and meaningful to study the thermal safety of hydrophobic silica aerogel.In this paper,three kind hydrophobic silica aerogels were prepared using tetraethyl orthosilicate as silicon source by atmospheric drying.They are MSA aerogel modified by MTCS,DSA aerogel modified by DMDCS and TSA aerogel modified by TMCS.We tried to reveal the differences in physicochemical properties and combustion behaviors between hydrophobic silica aerogels modified by different MCSs,and also studied the explosion behavior of TSA,which is the most dangerous.The main conclusions are as follows.（1）Different methylchlorosilanes have a great influence on the physicochemical properties of aerogels.Although the pore structure,microscopic morphology and hydrophobic angle of the three aerogels are relatively close,the density and thermal conductivity of the aerogels show a decreasing trend,while the porosity,specific surface area,thermal stability and calorific value of combustion all showed an increasing trend with the increase of methyl groups on the aerogels.（2）MSA,DSA and TSA all showed similar combustion behavior.With the increase of radiative heat flux,the ignition time decreased,while the fire spread rate,heat release rate（HRR）,peak of heat release rate（pk HRR）and total heat release（THR）were increased.Combined with fire growth rate and fire performance index,TSA has the greatest fire risk,followed by DSA,and MSA has the least fire risk.（3）In the study of the explosion characteristics of TSA aerogels,it is found that when the dust mass concentration is between 300 g/m³ and 1000g/m³,both the maximum explosion pressure and the maximum explosion pressure rise rating show a trend of first increasing and then decreasing,while the time to reach the maximum explosion pressure and the maximum explosion pressure rising rate are opposite.Under the action of a 2 KJ igniter,the maximum explosion pressure and the maximum explosion pressure rise rate of TSA both reached their maximum values at the dust mass concentration of～500 g/m3,which were 1.027 MPa and 132 MPa/s,respectively.The explosion index of TSA calculated to be as high as 35.83MPa·m/s,reaching the S_t3 hazard level,and the explosion degree was severe.