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Nanocomposites of poly(vinyl chloride) (PVC) have been prepared by solution intercalation method using both natural and modified kaolinites. Kaolinite was modified with dimethyl sulfoxide (DMSO) to expand the interlayer basal spacing. The characterization of PVC/kaolinite nanocomposites was made by X-ray diffraction (XRD) and transmission electron microscopy (TEM); the interactions between kaolinite and PVC was discussed by FTIR-ATR; the thermal stability was determined by simultaneous DTA/TG. FTIR-ATR confirms hydrogen bonds formed between dimethyl sulfoxide molecules and the inner surface hydroxyl groups of kaolinite. XRD and TEM results give evidence that kaolinite was dramatically intercalated into nanoscale and homogenously dispersed in the PVC matrix. Thermogravimetric analysis indicated that introduction of clay to the polymer network resulted in an increase in thermal stability. Ultraviolet (UV) absorbance experiments showed that nanocomposites have a higher UV transmission than PVC film. The Kissinger method was used for calculation the decomposition activation energy. The results have shown that activation energy values at both stages for PVC/kaolinite nanocomposite are higher than those of pure PVC, indicating that addition of kaolinite particles improves thermal stability of PVC.

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Poly(vinyl chloride) (PVC)/sepiolite nanocomposites were prepared using PVC and natural, organo-modified, acid-activated, and calcined sepiolite samples through the solution intercalation method. Thermogravimetric (TG) analysis, UV-vis spectrophotometry, Fourier transform infrared spectroscopy, and scanning electron microscopy were used to determine the thermal stability, optical behavior, interactions, and morphology of samples, respectively. The dispersion of sepiolite in the PVC matrix was examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The nanocomposites exhibited higher thermal stability than that of pure PVC. XRD and TEM results showed that sepiolite particles were dispersed in the nanoscaled PVC matrix. The UV-vis spectra showed that the transmission of nanocomposites increased with the sepiolite content and wavelength. The thermal degradation behavior of PVC was investigated by using TG analysis under nonisothermal conditions at different heating rates under a nitrogen atmosphere. The apparent activation energy of samples was determined by using the Kissinger method. The nanocomposite showed higher activation energy than that of pure PVC. The

Modification of sepiolite clay has been performed using triethoxy-3-(2-imidazolin-1-yl)propylsilane in the presence of toluene solution. The modified material was characterized by FTIR spectroscopy, XRD, and simultaneous DTA/TG analysis. It was found that the chemical bonding takes place between the hydroxyl groups and/or oxygen atoms within the structure of sepiolite and the silane group of the triethoxy-3-(2-imidazolin-1-yl)propylsilane by releasing the ethoxy groups to the solvent. Thermal decomposition of natural and modified sepiolites was carried out with a thermogravimetric analyzer. In TG and DTA analysis, during gradual heating in an oxidizing atmosphere, the modified sepiolite was oxidized, giving rise to significant exothermic peaks. The exothermic peak in the temperature range of 200−650 °C depended on the modifier loading and provided evidence of bond formation on the sepiolite surface. For natural sepiolite, a mass loss of 20.43% was observed up to 900 °C, whereas this value increased to 31.90% for modified sepiolite under oxygen atmosphere. Electrokinetic properties of the modified-sepiolite suspensions were also examined as a function of the initial electrolyte concentration and equilibrium pH using a Zeta Meter 3.0 instrument. To determine the adsorption capacity of modified sepiolite for metal ions, the experiments were examined as a function of pH, ionic strength, and temperature. The adsorption capacity of modified sepiolite increased with increasing pH and temperature, but ionic strength was found to have no significant effect. The experimental data were analyzed using the Langmuir and Freundlich adsorption models. Satisfactory agreement between the metal uptake capacities by the modified sepiolite was expressed in terms of the correlation coefficient (R 2). The Langmuir model represented the sorption process better than the Freundlich model, with R 2 values ranging from 0.9603 to 0.9977.

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