Flexible Nanofiber-Reinforced Aerogel (Xerogel) Synthesis, Manufacture, and Characterization

Abstract

Silica aerogels are sol-gel-derived materials consisting of interconnected nanoparticle building blocks that form an open and highly porous three-dimensional silica network. Flexible aerogel films could have wide applications in various thermal insulation systems. However, aerogel thin films produced with a pure sol-gel process have inherent disadvantages, such as high fragility and moisture sensitivity, that hinder wider applications of these materials. We have developed synthesis and manufacturing methods to incorporate electrospun polyurethane nanofibers into the cast sol film prior to gelation of the silica-based gel in order to reinforce the structure and overcome disadvantages such as high fragility and poor mechanical strength. In this method, a two-stage sol-gel process was employed: (1) acid-catalyzed tetraethyl orthosilicate hydrolysis and (2) base-catalyzed gelation. By precisely controlling the sol gelation kinetics with the amount of base present in the formulation, nanofibers were electrospun into the sol before the onset of the gelation process and uniformly embedded in the silica network. Nanofiber reinforcement did not alter the thermal conductivity and rendered the final composite film bendable and flexible.

Flexible organofunctional aerogels

“…Functional polyorganosilsesquioxane aerogels and xerogels were prepared via a co-condensation approach of methyltrimethoxysilane (MTMS) and an organofunctional trialkoxysilane RSi(OMe) 3 with a reactive functional group, e.g. R = vinyl (VTMS), chloropropyl (CPTMS), mercaptopropyl (MPTMS) or methacryloxypropyl (MAPTMS).…”

“…This can be achieved by aging the said aerogels in specific silane solutions, reinforcing the aerogels with fibers or by employing a polymer crosslinking approach. [2][3][4][5][6] Another promising way to improve the mechanical properties is to make aerogels hydrophobic by post-treatment with surface modification agents or by the hybridization of silica aerogels via a cocondensation approach of silicon alkoxides with organosilane precursors that contain hydrophobic groups. [7][8][9][10][11] Recently, different flexible organic-inorganic hybrid aerogels were made solely from a methyltrimethoxysilane (MTMS) or vinyltrimethoxysilane (VTMS) precursor.…”

“…[21][22][23] So far and to the best of our knowledge, there is no study published on the variability and accessibility of these functionalities. Herein, we describe the first systematic investigation of the co-condensation approach of MTMS and further organofunctional alkoxysilanes RSi(OMe) 3 with reactive functional groups, e.g. R = vinyl, chloropropyl, mercaptopropyl, and methacryloxypropyltrimethoxysilane, aided by a two-step acidbase sol-gel process.…”

Synthesis and characterization of flexible and high-temperature resistant polyimide aerogel with ultra-low dielectric constant

“…Adversely, for other porous gels, such as Xerogels prepared by common drying techniques, the gels are easily collapsed by capillary stress induced at the liquid-vapor interfaces during drying process, resulting in apparent shrinkage for the nanoporous gels (>30%). The porosity is usually lower than 60-80% and the k values are always higher than 1.50 [32,33]. The structural parameters for PI aerogel are tabulated in Table 1.…”

Needleless Electrospinning and Electrospraying of Mixture of Polymer and Aerogel Particles on Textile

“…A very limited number of reports are available where the electrospinning technique was used to combine both aerogel and textile [20,21]. Such approach is mainly to add electrospun nanofibre into the aerogel precursor before aerogel synthesis to produce fibrous aerogel.…”