Synthesis and characterization of 1,1-bis(3-methyl-4-hydroxy phenyl)cyclohexane polybenzoxazine–organoclay hybrid nanocomposites

Typical high-performance polybenzoxazines were prepared from benzoxazines based on 1,1-bis(3-methyl-4-hydroxy phenyl) cyclohexane, paraformaldehyde and three distinctive aromatic diamines, namely 4,4’-diaminodiphenylmethane, 4,4’-diaminodiphenylether and 4,4’-diaminodiphenylsulfone, through ring-opening self-polymerization upon heating. The formation of benzoxazines was confirmed by Fourier transform infrared, 1H and 13C nuclear magnetic resonance spectra. Polybenzoxazine–clay hybrid nanocomposites were prepared by a solvent method using polybenzoxazine precursors and organoclay (OMMT) (up to 5 wt.%). The hybrid mixture was subjected to ultrasonication for effective blending. The thermal properties of the resulting polybenzoxazine–clay nanocomposites were studied using differential scanning calorimetry and thermogravimetric analysis. The dispersion of OMMT in the polybenzoxazine and nanostructure of the composites was confirmed by X-ray diffraction analysis. The d spacing of the organoclay interlayers was found to be increased from 1.69 to 2.10 nm. Thermal decomposition temperatures of the nanocomposites were in the range 294–637 °C. These nanocomposites exhibited a high char yield relative to unfilled polybenzoxazines depicting interfacial interactions between the organic and inorganic phases. The homogeneous morphological behavior was studied by scanning electron microscopy.