Aerocellulose: Aerogels and Aerogel‐like Materials made from Cellulose

Abstract

Cellulose aerogels have been prepared starting from cellulose-NMMO solutions via the classical aerogel-path. Different cellulosic materials have been tested and their influence on the properties of the product aerogels has been studied. Other parameters that have been varied include solution composition as well as the way of cellulose regeneration (solvent and temperature). More than 300 different samples were prepared and analysed. Their density is in a typical range from 0.02 g/cm 3 to 0.2 g/cm 3 and their internal surface area ranges from 100 m 2 /g to 400 m 2 /g. Another property investigated in detail beside density and internal surface area was the shrinkage of the cellulosic bodies during the production process.

Ultralight-Weight Cellulose Aerogels from NBnMO-Stabilized Lyocell Dopes

“…• C and 100 bars compared to those cellulose bodies which were directly generated with ethanol (0.06 g/m 3 ) which is in accordance with previous reports [11].…”

“…Water-as the solvent usually used for industrial production of Lyocell fibers or films [11,19,20 fine-porous, fragile cellulose solute structure simultaneous to its reorganization into the cellulose II polymorph, and requires, moreover, solvent exchange steps with solvents such as ethanol or acetone if subsequent drying of the regenerated gel with supercritical CO 2 (scCO 2 ) is envisaged. The regeneration with water and subsequent solvent exchange affected the pore structure of the cellulose gel to some extent (see Figure 2(b)).…”

“…In 2004, Jin et al [10] were the first to use cellulose in the nonderivatized form; their approach produced film-like material of less than 1 mm thickness. Innerlohinger et al [11] and our group [12] applied also nonderivatized cellulose for aerogel production, but employed the procedure of directly dissolving the cellulose in N-methylmorpholine-N-oxide (NMMO) as it is commercially used for the production of Lyocell fibers. Although dimensionally stable cellulosic bodies were obtained with this approach, the regeneration procedure was hitherto rather lengthy and somewhat erratic with regard to the quality of the products, that is, the size and stability of the desired micropore structure and the chemical purity.…”

Transparent Aerogels with High Mechanical Strength Composed of Cellulose-silica Cross-linked networks

“…One solution is to fabricate cellulose aerogels [16][17][18][19] with interconnected open-porous network structures. However, they re light-tight, and the preparation process usually involves the utilization of toxic isocyanates.…”

A New Nanoporous Aramid Fiber Aerogel

“…They have been widely used as thermal or sound insulations, particle filters, particle trappers and adsorbents [6,11,12]. However, most of the aerogels share with the same shortage, which are described as their poor mechanical property [13].…”