In this work, monolithic silica aerogels were prepared in pure water within 4 h by using MTMS as the precursor under ambient pressure drying (APD). The effects of the volume ratio of H 2 O/MTMS, CTAB content and NH 3 ·H 2 O concentration on the properties of MTMS-based aerogels (MSA) were investigated experimentally. The realization of the rapid synthesis of MSA under APD is attributed to getting rid of the aging process, solvent exchange and surface modification. It demonstrates that the microstructure of MSA is comprised of coralloid branches. Furthermore, the greater volume ratio of H 2 O /MTMS, larger CTAB content and smaller NH 3 ·H 2 O concentration cause relatively slimmer coralloid branches, smaller pores and weakened connectivity of skeletons. It also finds that the MSA with a greater volume ratio of H 2 O/MTMS presents larger Young’s modulus and smaller compressive stress, which is because of the correspondingly different microstructures. The as-prepared MSA shows a low density of 0.064 g/cm 3 and a contact angle as high as 143.4°, which provides their potentials for some engineering applications.
Considering the low thermal stability and high flammability of polyurethane sponge (PUS) and the poor mechanical performance of methyltrimethoxysilane (MTMS) aerogels, their combination for improvement of characteristics was investigated. The density of prepared polyurethane sponge/MTMS aerogel (PUSMA) composites increased exponentially between 0.032 and 0.13 g/cm 3 with the MTMS aerogel content rising, and the thermal conductivity increased linearly between 36.5 and 44.3 mW/(m K). The good hydrophobicity was maintained with a contact angle up to 145.0°. Despite the combination being physical effects, the PUSMA composite presented improved mechanical properties with better integrality and increased elastic modulus. Thermogravimetric analyses suggested that the synergistic effect in the combination improved the thermal stability. The flame combustion probability and the peak heat release rate with flame combustion decreased significantly, implying enhanced flame retardancy of the PUSMA composite. This study from the perspective of composites provides new insight into the development of new high-efficiency aerogel-based thermal insulation materials.
危险品化学品经营许可证（带存储）