Improved mechanical and flame resistance properties of vinyl ester resin composites by lithium containing polyhedral oligomeric phenyl silsesquioxane

The mechanical and flame retardancy properties of vinyl ester resin (VER) composites containing lithium containing polyhedral oligomeric phenyl silsesquioxane (Li-Ph-POSS) are investigated. The bending test suggests that Li-Ph-POSS improves the mechanical property of the matrix. Compared with the pure VER, the bending strength and flexural modulus are improved by 42.9% and 18.9% with the addition of 3 wt% Li-Ph-POSS, respectively. And cone calorimeter test results indicate that Li-Ph-POSS endows the matrix good fire resistance. Three weight percent Li-Ph-POSS makes the heat release rate (HRR) decline by 32.4% compared with the pure VER. Besides, 3 wt% Li-Ph-POSS performs best on smoke suppression and declines the release of CO due to good char-forming effect of Li-Ph-POSS. The improvement of mechanical property and the slightly improved glass transition temperature (Tg) of VER composites confirmed the excellent compatibility between Li-Ph-POSS and the matrix. The flame retardant mechanism is revealed by Thermogravimetric coupled with Fourier transform infrared analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy analysis in detail. The work provides an optional method to prepare flame retarded VER with excellent mechanical properties.