Development of a clay-polymer compatibility approach for nanocomposite applications

Na-montmorillonite (Na-Mt) from Reşadiye Region of Turkey was modified by three different cationic and two different nonionic surfactants. The raw Na-Mt was purified before modification in order to remove mineral impurities other than Mt. The intercalation ability of surfactants into Na-Mt interlayer was investigated by X-ray diffractometry (XRD). Interaction of surfactant with Na-Mt surface was examined by various techniques involving Fourier Transform Infrared Spectroscopy (FTIR), thermal stability by Thermal Gravimetric Analysis (TGA), and the clay-polymer compatibility using surface energy and solubility parameters approaches. The present study was mainly focused on the evaluation of clay-polymer compatibility due to the lack of knowledge in this research field. It was found that different type of surfactants required different methodologies to evaluate the clay-polymer compatibility. It is proposed that the surface energy approach is very suitable for cationic surfactants used in this study due to their hydrophobic nature, however, such approach is not suitable for relatively less hydrophobic nonionic surfactants. The possibility of using the surface energy approach for cationic surfactants and that of solubility parameter for nonionic surfactants is discussed in the light of experimental data and theoretical considerations.