Clay exfoliation and polymer/clay aerogels by supercritical carbon dioxide

Abstract

Supercritical carbon dioxide (scCO2) treatments of a montmorillonite (MMT) intercalated with ammonium cations bearing two long hydrocarbon tails (organo-modified MMT, OMMT) led to OMMT exfoliation, with loss of the long-range order in the packing of the hydrocarbon tails and maintenance of the long-range order in the clay layers. The intercalated and the derived exfoliated OMMT have been deeply characterized, mainly by X-ray diffraction analyses. Monolithic composite aerogels, with large amounts of both intercalated and exfoliated OMMT and including the nanoporous-crystalline δ form of syndiotactic polystyrene (s-PS), have been prepared, by scCO2 extractions of s-PS-based gels. Also for high OMMT content, the gel and aerogel preparation procedures occur without re-aggregation of the exfoliated clay, which is instead observed for other kinds of polymer processing. Aerogels with the exfoliated OMMT have more even dispersion of the clay layers, higher elastic modulus and larger surface area than aerogels with the intercalated OMMT. Extremely light materials with relevant transport properties could be prepared. Moreover, s-PS-based aerogels with exfoliated OMMT could be helpful for the handling of exfoliated clay minerals.

A material characterization and embodied energy study of novel clay-alginate composite aerogels

“…(Scherer, 1998). In this case porosity was therefore estimated by calculating the theoretical porosity of each sample using Equation 4, using the methods of Rassis et al (2003), Longo et al (2013) and Wang et al (2014), where ρb is the bulk density of the sample and ρp is the overall particle density. The latter value was calculated based on the mass fraction of each component and particle density estimates of 2.5 g/cm 3 for bentonite (Kogel et al, 2006) and 1.59 for alginate (Aspinall, 2014).…”

Influence of clay modification process in polypyrrole-layered silicate nanocomposite

“…Lamellar clays of the montmorillonite (MMT) type have been the subject of considerable interest for the manufacture of polymer-clay nanocomposites. These inorganic/organic nanocomposites have new and enhancing properties that individual inorganic and organic components do not possess [4][5][6][7][8][9]. Conjugated or conductive polymers have emerged as a highly promising class of materials for various applications.…”

Monolithic Polymeric Aerogels with Organically Modified Clays and Graphite Oxide Nanofillers

“…In this paper, the preparation of innovative highly porous nanocomposite materials based on polymeric aerogel with organically modified montmorillonite (OMMT) and graphene oxide (GO) will be described.…”