CO2 has a readily accessible critical point and is a relatively inexpensive, non-toxic, and environmentally friendly solvent. Our research has shown that soaking commercial clays in supercritical CO2, followed by a rapid depressurization can produce significant clay dispersion without any additional modification of the clays or their modifiers. Clay dispersion has been achieved with a variety of different clays, with and without the presence of polymer
The extent of dispersion is characterized by a wide range of characterization tools, such as WAXD, SEM, TEM, rheology, tensile and permeability testing.
The scCO2-processed samples have been benchmarked with solution blended and melt-compounded PS nanocomposites. The results suggest that the supercritical CO2-processing produces significant dispersion and improves polymer-clay interactions. The low-frequency modulus of scCO2-processed PS/clay melts are more than an order of magnitude better than those prepared by solution blending and melt compounding, for the same clay loading.
[1] ‘Supercritical Carbon Dioxide-Processed Dispersed Polystyrene-Clay Nanocomposites.', Manitiu, Mihai; Bellair, Robert J.; Horsch, Steven; Gulari, Esin; Kannan, Rangaramanujam M. Macromolecules (web published), October 2008.
[2] 'Supercritical CO2 dispersion of nano-clays and clay/polymer nanocomposites', S. Horsch, G. Serhatkulu, E. Gulari, R. M. Kannan, Polymer, 47 (21) 7485-7496 Oct 4 2006
[3] ‘Structure and mechanical properties of supercritical carbon dioxide processed porous resorbable polymer constructs, Baker, KC, R. Bellair, M. Manitiu, HN Herkowitz, RM Kannan*, accepted, Journal of Mechanical Behavior of Biomedical Materials, September 2008.
[4] ‘Engineering Strength, Porosity, and Emission Intensity of Nanostructured CdSe Networks by Altering the Building-Block Shape.', Yu, Hongtao; Bellair, Robert; Kannan, Rangaramanujam M.; Brock, Stephanie L. Journal of the American Chemical Society (2008), 130(15), 5054-5055
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