Formation of clay intercalates with organic bilayers in hydrocarbon polymers

Abstract

The formation of clay intercalates with three different kinds of organic ammonium salts, when mixed in the presence of synthetic or natural polyisoprene rubber, has been investigated. X‐ray diffraction and transmission electron microscopy (TEM) experiments have shown that intercalates with organic bilayers, rather than with interdigitated organic monolayers, are obtained only for the ammonium salts presenting two long alkyl chains and only in the presence of the natural rubber (NR). These results have been qualitatively rationalized on the basis of suitable interlayer densities. Both monolayer and bilayer clay intercalates remain stable for short‐term heating procedures at temperatures lower than 250°C. For treatments at higher temperatures, where the decomposition of the organic ammonium salt occurs, both kinds of clay intercalates maintain intralayer crystalline order. However, the decomposition of the organic modifier leads to the formation of pristine and exfoliated clay for the intercalates with organic monolayers and bilayers, respectively. Copyright © 2008 John Wiley & Sons, Ltd.

Rubber Clay Nanocomposites

“…The preparation of the organoclay in situ in the rubber matrix was reported by Galimberti [57,[64][65][66][67], by adopting the melt blending approach, with all the processing technologies mentioned in paragraph 5.2. An even clay dispersion was achieved in the rubber matrix and the organoclays revealed a lower number of stacked layers.…”

Clay exfoliation and polymer/clay aerogels by supercritical carbon dioxide

“…CPN exhibiting exfoliated clays are difficult to attain, particularly in the case of non-polar polymers (Choi et al, 2004; Robello et al, 2004; Chou and Lin, 2005; Galimberti et al, 2007, 2009, 2010). …”

Reinforcement of diene elastomers by organically modified layered silicates

“…An accurate quantitative determination of interlayer distance performed on TEM images brought to obtain a value of about 7 nm, very close to the one assessed from XRD analysis [14].…”

“…In the light of this concept, the formation of crystalline clay intercalates with organic mono-layers is easily understandable. A density high enough to allow the formation of a bi-layer structure can be achieved thanks to the cooperation of the two long hydrocarbon chains of the ammonium salt and of polar molecules, minor components of the natural rubber, that can segregate in the inter-layer space [14]. In conclusion, by melt blending a diene rubber, a pristine layered clay and an ammonium salt as the organic modifier, clay intercalates with organic mono-and bilayers are formed without evidences for the intercalation of polymer chains between the layers.…”