Epoxy Reinforced Aerogels Made Using a Streamlined Process

Abstract

Reinforcing silica aerogels by conformally coating the nanoskeleton with a polymer has been demonstrated to be an effective way to improve mechanical properties. In addition, the mesoporosity and low thermal conductivity is maintained, making this robust form of aerogel an enabling material for a variety of aerospace applications. However, the process for making the aerogels can be quite long, involving production of the gel, solvent exchanges, and diffusion of monomer, followed by more solvent exchanges and supercritical fluid extraction. This paper for the first time compares a synthetic scheme that shortens the process to make epoxy reinforced aerogels by eliminating monomer diffusion and half of the solvent washes to the previously described diffusion-controlled process. The ethanol-soluble epoxy monomers are included in the initial step of the sol−gel process without interfering with gelation of the starting silanes. Notably, properties of aerogels made using a low amount of amine reactive sites have properties similar to those previously reported that used the longer diffusion controlled process, whereas higher amounts of amine sites produce less desirable monoliths with much higher density and lower surface areas.

Synthesis and biomedical applications of aerogels: Possibilities and challenges

“…Meador et al [128] introduced epoxy monomer in the initial sol, Wingfield et al [129] used an acrylic monomer and Duan et al [130] used a custom-synthesized, water-dispersible urethane oligomer. Recently, White [131] shortened the aerogel composite fabrication by conducting the experiment with simple one pot approach and using the more economic-friendly ethanol-water azeotrope mixture as gelation solvent.…”

Elastic silica aerogel using methyltrimethoxysilane precusor via ambient pressure drying

“…Recently, progresses have been made in improving the strength and toughness of silica aerogels by integrating high strength fibers [11][12][13][14] or cross-linking silica aerogels with polymers [15][16][17][18]. On the other hand, Sarawade et al [19] successfully synthesized aerogels with high specific surface using tetraethoxysilane (TEOS) as precursor at ambient pressure.…”

Strengthening silica aerogels with surface initiated ATRP cross-linked poly(methyl methacrylate)

“…Recent efforts to prepare robust aerogels have utilized a reinforcing agent to the "necks" between particles in the aggregate structure. Chemical modification can be performed after the aerogel has been dried through vapor deposition of reactive chemicals [8][9][10] or before drying through polymerization of monomers in the alcogel [11][12][13][14][15][16][17][18][19]. In the latter case, attaching reactive groups on the surface of the silica particles to help restrict the growth of polymeric species to where they are needed to reinforce the network has been shown to be effective.…”