The flame‐retardant rigid polyurethane foam (RPUF) composites are fabricated by ammonium polyphosphate (APP) with pentaerythritol phosphate (PEPA), phenoxycycloposphazene (PCP), and aluminum diethylphosphinate (ADP), respectively, which are labeled as RPUF‐1, RPUF‐2, and RPUF‐3. The influence of flame retardants on the apparent density and compressive strength of RPUF is studied. The results reveal that flame retardants not only improve the apparent density, but also improve the compressive strength of RPUF composites. The limiting oxygen index (LOI) results reveal that these inorganic/organic phosphorus‐based flame retardants improve the LOI significantly, especially for RPUF‐2 and RPUF‐3 systems. The cone calorimeter test results suggest that the peak of heat release of RPUF‐1, RPUF‐2, and RPUF‐3 systems decrease by 38%, 41%, and 52% likened to that of pure RPUF. And APP and ADP system performs best in declining the heat release. And APP and PEPA systems perform best in decreasing the smoke release. The flame retardancy mechanism of RPUF composites is analyzed in details.

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.

The ladder phenyl/vinyl polysilsesquioxane (PhVPOSS) was used to improve the flame-retardancy performances of ethylene-vinyl acetate copolymer (EVA)/aluminum hydroxide (ATH) composites due to the reactivity of its vinyl groups. FTIR, XPS, 1H NMR, and SEM-EDS data demonstrated the PhVPOSS grafting onto EVA molecular chains. The PhVPOSS improved the thermal stability of EVA/ATH composites, as shown by the thermogravimetric analysis (TGA). Furthermore, with the cone calorimeter (CONE) experiments, EVA/ATH/PhVPOSS showed better fire safety than the EVA/ATH composites, with the PHRR, PSPR, and PCOP reduced by 7.89%, 57.4%, and 90.9%, respectively. The mechanism investigations of flame retardancy revealed that the charring behaviors of the EVA/ATH/PhVPOSS composites were improved by the formation of Si-C bonds and Si-O bonds, and a more compact and denser char layer can contribute more to the barrier effect.