The role of exfoliated kaolinite on crystallinity, ion conductivity, thermal and mechanical properties of poly(ethylene oxide)/kaolinite composites

Kaolinite particles were exfoliated by the intercalation and subsequent deintercalation of urea in the interlayer of kaolinite. The exfoliated kaolinite particles were used to prepare a novel poly(ethylene oxide)/kaolinite (PEO/kaolinite) composite. The resulting exfoliated kaolinite and PEO/kaolinite composites were characterized by X-ray diffraction (XRD), Fourier transfer infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), ion conductivity test, thermogravimetry (TG) analysis and mechanical test. XRD results showed that the 001 diffraction of kaolinite in the XRD pattern almost disappeared after exfoliation treatment. FTIR spectra showed that the inner surface hydroxyls of kaolinite decreased after exfoliating kaolinite layers. SEM micrographs confirmed the exfoliation of kaolinite particles and showed a good dispersion of exfoliated kaolinite in PEO matrix. A gradual decrease in PEO crystallinity in PEO/kaolinite composites was observed with the increment of the exfoliated kaolinite concentration by DSC test. The ion conductivity of the composites gradually increased with exfoliated kaolinite content and reached 6.1 x 10(-5) (S/cm) at a filler concentration of 20 wt%. The formation of amorphous region around the exfoliated kaolinite was beneficial for the Li+ ion conduction. Thermogravimetry analysis showed that the decomposition temperature of PEO matrix at weight loss of 10 and 50 wt% was increased when exfoliated kaolinite was introduced into PEO matrix. In addition, the mechanical properties of PEO matrix were also enhanced when exfoliated kaolinite content in PEO matrix was no more than 15 wt%.