Structure and thermal stability of organo-vermiculite

Abstract In this study, organo-vermiculites (HEVrm) were prepared by modifying expanded vermiculite (EVrm) with different amounts of surfactant (hexadecyltrimethyl ammonium bromide, HDTMAB). The obtained HEVrm were characterized by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TG). Instead of a gradual increase of the basal spacing for organo-montmorillonite (OMt) as reported in literatures, a one-stepped increase of the basal spacing was observed for HEVrm. As such, the intercalation of surfactant into the interlayer space of EVrm is not homogeneous. In particular, only part of the interlayer spaces of EVrm were intercalated by surfactants at low HDTMAB concentration; with the increase of surfactant concentration, more and more interlayer spaces were intercalated, reaching a “saturation” state at last. The intercalated surfactant adopted a paraffin-monolayer arrangement with all-trans conformation within the interlayer space. The decomposition temperature of the intercalated surfactant in HEVrm is very similar to that of neat surfactant. The protection of the clay mineral layers for the thermal stability of the intercalated surfactant is not obvious, which is very different from that for OMt. This may be due to the one-stepped increase of the basal spacing in HEVrm with relatively large interlayer height. These findings are of high importance for preparation and application of HEVrm.