In order to meet the rising demands of applications for new materials, hybrids of inorganic clays and polymeric materials are being constantly developed. Polymer–clay composites have attracted a great deal of interest due to their unique properties. Sepiolite is a kind of hydrated magnesium silicates structurally consisting of internal channels capable of accommodating water and other molecules. Hydroxyl in the surfaces of sepiolite made it not easy to cohere with polymer. In order turn its hydrophilic properties to hydrophobic properties, cationic surfactant cetyltrimethyl ammonium bromide (CTAB) were used to modify sepiolite. The results of FT-IR and XRD experiments showed that CTAB could turn into the internal channels and modify the surfaces of sepiolite. The interlayer spacing of sepiolite modified by CTAB (d110=1.241 nm) increased slightly as compared to the pristine sepiolite (d110=1.224 nm). Polystyrene/sepiolite composites, based on organo-sepiolite and styrene monomer were synthesized by suspension polymerization. The results of FT-IR showed that polystyrene in the composite was atactic polystyrene. Experiment results proved that the major influencing factors on thermal stability of composite were the diffusion of the polymer chains into the sepiolite agglomerates. Differential scanning calorimetry (DSC), Differential thermal analysis (DTA) and Thermogravimetric analysis (TGA) results indicated that the glass transition temperature and initial decomposition temperature of the composite increased after adding the organo-sepiolite modified by CTAB. The composite glass transition temperature increased 9.6ºC, and initial decomposing temperature increased 5 ºC by adding 0.5 wt % organo-sepiolite modified by CTAB. This work is supported by grants from the Jiangxi Provincial Natural Science Foundation of China (No. 0420032).

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