Double organic groups-containing polyhedral oligomeric silsesquioxane filled epoxy with enhanced fire safety

To simultaneously improve the flame retardancy, smoke suppression, mechanical properties, and dielectric properties of epoxy resin (EP), a series of polyhedral oligomeric silsesquioxane containing vinyl and epoxy groups (EV-POSSs) was designed and successfully synthesized. The results of Fourier transform infrared (FT-IR), Nuclear Magnetic Resonance (NMR) and mass spectra indicated that the EV-POSSs possessed two main cage structures, T₁₀ and T₁₂. The epoxy groups attaching to POSS connected the polymer main chains, forming higher crosslinking-density networks. The self-polymerization of vinyl groups under high temperatures improved the mechanical property and the quality of char residues. Based on our study, the introduction of EV-POSSs can enhance the flame retardancy, smoke suppression, mechanical and dielectric properties. Compared with pure EP, the dielectric constant of EP containing 2 wt% EV-POSS dropped from 3.9 to 3.6 at 10⁶ Hz. In addition, with the 10 wt% EV-POSSs, the peak of heat release rate and total smoke production also reduced by 50.7% and 36.7%, respectively. Most notably, the maximum smoke density declined by 44.8% due to the EV-POSSs simultaneously containing epoxy and vinyl groups show comprehensive enhancement and occupy spacious applications.