Thermal decomposition of phenoxy/clay nanocomposites: Effect of organoclay microstructure

The influence of organoclays on the thermal decomposition pathway of poly(hydroxyl ether of bisphenol A) (Ph) was analysed under nitrogen and air. In the two clays employed, montmorillonite and vermiculite, the organic clay modifier, a polar alkylammonium surfactant, led to different interlayer arrangements. Nanocomposite formation was established by X-ray diffraction and transmission electron microscopy. Thermal degradation of phenoxy and its nanocomposites was analysed by thermogravimetry (TGA/DTGA) and the evolved gases were investigated using thermogravimetric analysis coupled with Fourier transform infrared spectroscopy (TGA/FTIR). In both inert and oxidative atmosphere, it was observed that for the same organoclay proportion, nanocomposites containing organo-modified montmorillonite (Cloisite 30B) decompose at higher temperatures than those containing organo-modified vermiculite (VMT-ETO). This behaviour was attributed to the presence of the original metallic cations as a consequence of the incomplete exchange obtained in the organic modification of vermiculite. FTIR spectra of the evolved gases demonstrated that the incorporation of organoclays into phenoxy resin does not modify the degradation pathway of phenoxy, although the decomposition of the matrix is accelerated, possibly as a consequence of acidic sites created in organical decomposition.