Destabilization of Natural and Commercial Bentonite Interlayers by Ultrasonication, pH Control and Salt Addition

Abstract

Natural and commercial bentonites can act as efficient fillers to reinforce a polymer matrix if their strong interlayer binding forces are weakened to reduce tactoid formation. In this research, interlayers destabilization process was applied to gain a loosely packed, swelled and disorganized clay layered structure for better polymer intercalation and filler dispersion during the polymer/clay composite fabrication. Three different destabilization methods were applied to the natural and commercial bentonites and their effects on swelling and platelets ordering/stacking of the clays were observed. The pristine and destabilized natural and commercial bentonites were characterized and compared based on their chemical component (XRF), chemical structure (XRD) and morphology (FESEM). Chemical analysis revealed that alumina content in the natural bentonite is less than in the commercial bentonite while silica content in natural bentonite is more than in the commercial bentonite. XRD results suggest that basal spacing (d001) of both natural and commercial bentonites reduced when single destabilization process (by salt addition) was applied but increased when destabilization was done by the combination of pH control and salt addition processes. These show that the destabilization process through combination of pH control and salt addition is more efficient in swelling both natural and commercial bentonite clays. This is supported by FESEM analysis where smaller, more loosely packed and uniform platelets were observed due to swelling and weakening of the interlayer binding forces of both natural and commercial bentonite clays.

Ethylene vinyl acetate nanocomposites with hybrid silicate nanofillers of destabilized natural and commercial bentonites and organomontmorillonites

“…Besides, the ultrasonication process can induce the formation of porous agglomerate structures of bentonite because sonic wave helps to disorganize its platelets. Kelessidis also stated that a loosely packed tactoid can be formed when a salt is added to the bentonite due to the formation of a diffuse electric double layer around the clay platelets, which produce a resistance movement of clay platelets forming “electroviscous effect.” Another research by Abdul Hamid et al and Fauzi et al also stated that ultrasonication helps to create clearer porous agglomerate structures, which enhance the disorganized platelets . Besides, sonic waves also help to disorganize the platelets, thus inducing the formation of porous agglomerate structures of the bentonites.…”

“…b). This could be due to the dissolution of the Al 3+ during the destabilization process in the water medium . Consequently, there would be greater cationic substitutions in the octahedral layer that brought destabilization effects to both types of bentonite.…”