ENHANCEMENT OF LAYERED NANOCLAY PROPERTIES BY MEANS OF A TREATMENT WITH SUPERCRITICAL CARBON DIOXIDE

摘要

Nanocomposite polymeric materials are a new generation of plastic materials with interesting final application properties for diverse industrial sectors. Nowadays, nanocomposites tend to use silicated layered nanoclays, that present two main problems: high price, due to low efficiency of processing; and low final efficiency in nanocomposites, due to dispersion limitations. Thus, research still looks for new nanoclay processing to optimise final prices and to increase final nanoclay yield in nanocomposites. In this context, supercritical fluid technology may play an interesting role as an alternative for nanoclay modifying/processing. Under supercritical conditions, SCF's may diffuse and enter into the interstitial silicate spaces. This way, SCF's may be used to optimise the separation of nanoclays or as a reaction medium to apply functional chemical groups to change their properties. Experimental test were performed with bentonite samples at two supercritical facilities, at pressures up to 270 bar and temperatures up to 55 °C. SC-CO_2 treated bentonite samples with very different properties from those of the original non-treated material were achieved. The most significant change was observed in the absorbed water (TGA) and FTIR measurements. Treated bentonite samples exhibited higher specific surface, lower interlaminar water, and higher viscosity were achieved in water suspensions of nanoclays.