Enhanced fire safety and mechanical properties of epoxy resin composites based on submicrometer-sized rod-structured methyl macrocyclic silsesquioxane sodium salt

Facile synthesis of multifunctional macromolecules endowed with low cost has always been a considerable challenge for chemists. Herein, a series of methyl macrocyclic oligomeric silsesquioxane sodium salt (Na-MOSS) were synthesized via the simplified one-pot method. FTIR, NMR, MALDI-TOF MS and XRD results suggested that Na-MOSS endowed with well-defined macrocyclic structure and highly crystalline. The directly obtained Na-MOSS powder crystals were proved to be submicrometer rod-like morphology. TGA results indicated that the initial decomposition temperature and residual weight at 800 °C of Na-MOSS were 427 °C and 89.6%, respectively. These results implied that Na-MOSS enjoyed superior thermal stability. Notably, we firstly discovered that the pyrolysis condensed products of Na-MOSS could react with N₂. Thereafter, the synthesized Na-MOSS was introduced into epoxy resin (EP) to improve the fire safety and decrease smoke hazards. Based on the cone calorimeter test results, with the incorporation of 2 wt% Na-MOSS, the peak of smoke production rate (p-SPR) and total smoke production (TSP) of EP/2 wt% Na-MOSS were apparently decreased by 50% and 36% compared with EP. Additionally, the storage modulus, flexural strength and modulus values of EP/Na-MOSS were higher than EP. The incorporation of Na-MOSS can apparently reduce the dielectric constant and loss of composites. These results indicate that EP/Na-MOSS enjoy better flame retardant, dielectric and mechanical properties and is more suitable for practical applications. Overall, our findings provide a class of overwhelmingly promising multifunctional rod-like macrocyclic organic–inorganic hybrid materials. Such materials can alleviate fire hazards and improve mechanical performance of EP composites.