Effect of additives on the properties of silica based aerogels synthesized from methyltrimethoxysilane (MTMS)

•MTMS–derived aerogels dried by continuous supercritical fluids extraction with CO2.•Effect of three additives on the properties of obtained silica based aerogels.•Poly(ethylene glycol) acts as a porogen, giving lower density/thermal conductivity.•Bis(trimethoxysilyl) hexane allowed faster and complete gelation of large samples.•Trimethoxy(octadecyl) silane improved aerogels flexibility and reduced dust release.

Aerogels are regarded as one of the most effective thermal insulation materials. Starting from methyltrimethoxysilene (MTMS) as sol–gel precursor, the supercritically dried silica based aerogels exhibit very low density and thermal conductivity, high hydrophobicity and remarkable flexibility, meeting the requirements for weight-sensitive insulation applications, e.g. for Space environments. However, further improvement in the properties of MTMS–derived aerogels may be achieved by using small amounts of additives/network modifiers in the synthesis. In this work, poly(ethylene glycol) (PEG), bis(trimethoxysilyl) hexane (BTMSH) and trimethoxy(octadecyl) silane (ODS) were investigated for this purpose. Whereas PEG allows for manipulation of the pore size distribution, leading to a decrease in bulk density of the aerogel, BTMSH reinforces the gel structure links, increasing its homogeneity and cohesion and reducing the dust release. The effect of the long length of alkyl substituent group of ODS resulted on an increased flexibility and reduction of particle shedding of the aerogels.

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