Powdered samples of montmorillonite were functionalized with ammonium surfactants of various chain lengths and subjected to two different constant volume washing procedures: water only or sequential ethanol-water. The organo-functionalized montmorillonite materials were analyzed with two widely used quantitative materials characterization methods (X-ray diffraction and differential scanning calorimetry) to obtain insights into the effect of washing procedure. Both analysis methods provided consistent results that allowed the materials washed by the two procedures to be distinguished. Particularly noteworthy was the differential scanning calorimetry result for montmorillonite functionalized with n-octadecyl ammonium chloride followed by water washing, which exhibited two sharp peaks during the first heat indicating the presence of crystallographic order in the ammonium surfactant between the galleries. This result had not been observed in earlier published results and is attributed to the sensitivity of the inter-layer morphology to the washing procedure. It was determined that the ethanol-water procedure greatly reduced the amount of surfactant present that was not electrostatically associated with the montmorillonite. Compacted samples of the powdered materials were also prepared for a contact angle study to assess the effect of functionalization and washing on the wettability of common epoxides used in preparing epoxy-based, clay nano-composites. Regardless of surfactant treatment, clay specimens with ethanol-water washing exhibited lower contact angles for either epoxide, which is consistent with lower final surfactant content. Surface porosity and particle agglomeration of selected compacted-powder samples were examined using atomic force microscopy.
Citation: Applied Clay Science
Pub Type: Journals