JOINT TREATMENT OF BENTONITES WITH INORGANIC POLYELECTROLYTES AND CATIONIC SURFACTANTS IN ORDER TO PROMOTE ORGANOCLAY EXFOLIATION

Abstract

A new approach to production of organomodified bentonites is offered. Bentonites are consecutively treated with inorganic polyelectrolyte (sodium silicate solution) and quaternary ammonium salts, as a result exfoliated organoclays are obtained. An ejector set up has been used for treatment of natural bentonites. Samples of activated bentonites treated in the ejector set up with sodium silicate solution (up to 21 g of sodium silicate per 100 g of bentonite) were prepared. Structure of the obtained bentonite and organoclay samples was established by X-ray diffraction analysis. It has been shown that treatment of the activated bentonite with sodium silicate does not influence the structure of the non-modified bentonite particles, but facilitates exfoliation of clay after organomodification. Polymer composites based on EVA containing 5% wt. of bentonites were prepared by extrusion mixing. In case of non-modified bentonites microcomposites are formed. In case of organomodified bentonites, not treated with sodium silicate, intercalated nanocomposites are formed. Treatment of bentonite with sodium silicate solution and subsequent organomodification ensures the production of exfoliated nanocomposite. Mechanical properties of obtained polymer composites were determined. Incorporation of 5% wt. clays or organoclays into the polymer material leads to increase in Young modulus (up to 50%), tensile strength (up to 20%); elongation at break decreases by 10% or less. In order to ensure the more significant reinforcing effect in EVA composites optimization of the organomodified bentonite composition (selection of surfactant and its content in the organoclay) has to be carried out with account for the polymer properties.