Reducing the thermal hazard of hydrophobic silica aerogels by using dimethyldichlorosilane as modifier
Reducing organic groups on hydrophobic silica aerogels (SA) is worth exploring for lowering their thermal hazard risk. In this work, we used dimethyldichlorosilane (DMDCS) to modify silica alcogels, investigated the effects of DMDCS concentration and focused on the thermal hazard assessment of the DMDCS modified SA (DSA). It was turned out that the DSA had less −CH3 content in spite of the thermal stability close to the trimethylchlorosilane modified SA (TSA), about 240 °C. The kinetics study suggested the apparent activation energy (Ea) could be divided into two segments, corresponding to the two processes in the pyrolysis. The positive enthalpy and entropy changes indicated that the thermal oxidation of the DSA was an exothermic reaction, which could not occur without external energy supply. The average Ea of the DSA was far larger than that of the TSA and the gross calorific value of the DSA decreased by about 12% compared with that of the TSA. All these results drew a conclusion that the DMDCS modified SA reduced the thermal hazard to some degree, which provided one possible solution to further lower the thermal hazard of hydrophobic SA.
Dimethyldichlorosilane modified silica aerogels (DSA) were prepared at the optimum concentration of 4%.
Kinetic and thermodynamic behavior of DSA were studied in detail.
DSA has larger apparent activation energy than trimethylchlorosilane modified silica aerogels (TSA).
DSA has lower thermal hazard than TSA for a less gross calorific value.
KeywordsHydrophobic silica aerogels Thermal hazard Dimethyldichlorosilane Kinetics Thermodynamic parameter
This work was supported by the National Natural Science Foundation of China (No. 51904336), the Fundamental Research Funds for the Central Universities (Nos. 202501003 and 202045001) and the China Scholarship Council (No. 201806375007). Furthermore, we really appreciate the anonymous reviewer for the constructive comments and the co-editor Florence Babonneau for the resubmission opportunity.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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