Characterization, thermal and mechanical properties and hydrophobicity of resorcinol-furfural/silicone hybrid aerogels synthesized by ambient-pressure drying†
Abstract
Organic aerogels generally exhibit poor thermal, mechanical and hydrophilic properties, which seriously restrict their large-scale applications. In this study, siliane was introduced into resorcinol-furfural (RF) aerogels due to the enhancement of silicone to thermal stability and hydrophobicity of polymer molecules. Resorcinol-furfural/silicone (Si–RF) hybrid aerogels were synthesized by sol–gel polycondensation of resorcinol, furfural, (3-aminopropyl) triethoxysilane (ATPES) and methyltrimethoxysilane (MTMS), followed by ambient pressure drying (APD). The Si–RF aerogels showed an interpenetrating framework with high mesoporosity. Silicon-containing functional groups were successfully incorporated into the RF aerogels in dehydration reactions. Surface area, characteristic thermal degradation temperature and char yield of the Si–RF aerogels are higher than that of the as-prepared RF aerogels. In order to improve the mechanical properties, carbon fabric reinforced Si–RF aerogel composites were prepared by impregnating a carbon-bonded carbon fiber (CBCF) composite with the hybrid aerogels. The obtained composites possessed a low bulk density (0.309–0.375 g cm−3), high compressive strength (0.759–2.940 MPa for different directions) and low thermal conductivity (0.085–0.136 W (m−1 K−1)). Hydrophobic aerogels were also fabricated by –Si(CH3)3 (trimethylsilyl substituent) modification via immersing fresh Si–RF aerogels in trimethylethoxysilane (TMES)/hexane solution followed by aging and APD. The hydrophobic property was promoted by the concentrations of solutions (water contact angle of about 108–135°), also the thermal stability.