Thermal and mechanical properties of POSS-Cyanate ester/epoxy nanocomposites

A new cyanate ester functionalized polyhedral oligomeric silsesquioxane (POSS-Cy) monomer was prepared by reacting hydroxyl functionalized POSS-OH with cyanogen bromide (CNBr) in the presence of triethylamine (Et₃N). The precursor POSS-OH and the corresponding cyanate ester POSS-Cy were characterized by Fourier transform infrared (FTIR), ¹H and ¹³C nuclear magnetic resonance (¹³C-NMR) spectral techniques. Nanocomposites were prepared by reacting diglycidylether of bisphenol-A, POSS-Cy and 4,4’-diaminodiphenylmethane (DDM). The structure of the cross-linked networks was confirmed by FT-IR. The POSS particles formed clusters in some regions leading to phase separation as revealed by scanning electron microscopy (SEM) analysis. Dynamic mechanical analysis (DMA) shows that the glass transition temperature decreases from 161^oC to 155^oC when the POSS-Cy content was increased from 0% to 15%. But, the T_10% of the epoxy resin (369^oC) increased significantly (404°C) on incorporating 15% of POSS-Cy. The LOI values indicate that these blends have good flame-retardant properties.