Hybrid organo-montmorillonite produced by simultaneous intercalation of phosphonium and ammonium/amine based surfactants

This study describes the preparation and characterization of hybrid organo-modified montmorillonite (OMt) produced by intercalation of phosphonium-based plus ammonium and/or amine-based surfactants, aiming to improve thermal and compatibility properties for the manufacture of clay mineral polymer nanocomposites (CPN). The choice of the surfactants was based on previous studies, which have pointed out that the phosphonium-based surfactant provided the clay mineral a high thermal stability but low d001-value and hydrophobicity. On the other hand, ammonium-based compounds presented inverse properties, i.e., low thermal stability and high d001-value. The present work was supported by design of experiments (DOE) considering different surfactant concentrations. The materials were analyzed by thermogravimetric analysis (TGA) to evaluate the thermal stability and relative reactional yield, by X-ray diffraction (XRD), to evaluate the surfactant intercalation by d001 of the clay, also by Fourier-transform infrared spectroscopy (FTIR) and contact angle, to verify the components interaction and the hydrophobicity. The hybrid montmorillonites presented intermediate properties, as thermal stability and basal space, when compared with the clay modified by the single modifiers. The intercalated species were arranged in paraffin-type structure and their conformation and tilt angle changed by increasing the ammonium concentration. Statistical analysis allowed knowing the concentration effects of each surfactant on hybrid materials. From the statistical models, an optimized formulation considering the maximum d001-value, Tonset (initial temperature of thermal degradation) and yield responses was prepared, which had its significance tested by Anova and F-test, and was validated by experimental values.