Inorganic/organic hybrid nanocomposites involving OMMT clay and cyanate ester-siloxane-modified epoxy resin: Thermal, dielectric and morphological properties

Inorganic-organic hybrid nanocomposites were prepared by the following steps: (1) homogeneous dispersion of various percentages (1 to 5% w/w) of organically modified montmorollonite clay in epoxy matrix resin1 (2) the resulting homogeneous epoxy-clay hybrids were modified with 10 wt.% of hydroxyl-terminated polydiemthyl siloxane (HTPDMS) using γ aminopropyltriethoxysilane (γ APS) as coupling agent in the presence of dibutyltindilaurate catalyst1 and (3) the siliconized epoxy-clay prepolymers were further modified separately with 10 wt% of three different cyanate ester monomers and cured with diaminodiphenylmethane. The chemical interactions between epoxy, clay, HTPDMS and cyanate ester were confirmed by Fourier transform infrared spectral analysis. The values obtained from differential scanning calorimetry and dynamic mechanical analysis showed that there was a significant loss of glass transition temperatures in the resulting hybrid epoxy nanocomposite systems compared with that of neat epoxy system. The inorganic clay mineral and the formation of thermally stable oxazolidinone structures and siloxane linkages during curing led to significant improvement in the thermal properties of the resulting nanocomposites. A decreasing trend was identified in the resulting nanocomposites from their values of dielectric constant and dielectric loss by the incorporation of clay, HTPDMS and cyanate ester in the epoxy resin. The intercalation/exfoliation structure was studied using X-ray diffraction analysis and the homogeneous/heterogeneous morphology was studied using scanning electron microscopy analysis in the resulting nanocomposites.