▎ 摘　　要

A comparison of ammonium polyphosphate/montmorillonite nanocompound (AM) and a synergistic agent, boron/silicate-based graphene oxide (B-Si@GO), is performed in unsaturated polyester resins (UPR) on flammability and thermal properties. It is found that by the presence of 14.9 wt% AM and 0.1 wt% B-Si@GO, the limiting oxygen indices value of 0.1 B-Si@GO/flame-retardant-UPR (FRUPR) composites is increased to 28.5%, and the UL 94 rating of V-0 is achieved. And, lower loading of B-Si@GO is observed to improve char skeleton, resulting in better insulation of the char and decrease in heat release, and the synergism of AM and B-Si@GO reduces the fire risk. Furthermore, by analyzing the pyrolysis behavior and mechanical properties of materials, B-Si@GO significantly improves the effects of flame retardants on the thermal stability, decomposition activation energy, tensile strength, and elastic modulus of UPR. Finally, flame retardant mechanism and model are proposed on the basis of the analyses of thermal decomposition products and process, and residual char structural components. This work provides a solution to improve the flame retardancy of UPR without affecting its mechanical properties, and will be conducive to the development of its flame retardant mechanism.