Silica aerogels having high flexibility and hydrophobicity prepared by sol-gel method

Highly flexible and hydrophobic silica aerogels were synthesized using methyltriethoxysilane and polydimethysiloxane as precursors via two-step acid–base catalyzed sol-gel and supercritical drying. The effects of different precursor and catalyst content on mechanical properties, thermal properties, and contact angles of aerogels were investigated. The aerogels prepared here can be compressed to as high as ~50% of original length and recovered back to their original length. The aerogels showed the hydrophobicity with a water contact angle of 145.6° and low thermal conductivity of 0.0338 W/(mK). Thermal gravimetric analysis shows that the aerogels were thermally stable up to 350 °C. The mechanical and thermal mechanisms of the silica aerogels were also studied. The prepared silica aerogels that were highly flexible, hydrophobic, and lightweight can be applied in thermal insulation of irregular parts, such as pipelines and outdoor attire that are exposed to moist circumstances as well.