The flammability of epoxy resins and knowing how to achieve curing are particularly important factors during use. A novel approach for enhancing the fire resistance and reducing the smoke emission of epoxy resin during the curing process is suggested, which involves the utilization of a three-source integrated polymerization intumescent flame-retardant. In this study, the synthesis of poly 4,4-diaminodiphenylsulfone spirocyclic pentaerythritol bisphosphonate (PCS) is achieved through using solution polymerization, utilizing 4,4′-diaminodiphenylsulfone (DDS) and spirocyclic pentaerythritol bisphosphorate disphosphoryl chloride (SPDPC) as initial components. Following that, the EP underwent the inclusion of PCS to examine its resistance to heat, its ability to prevent flames, its effectiveness in reducing smoke and its curing effect. Compared to the unmodified epoxy resin, the addition of PCS can not only cure the epoxy resin, but also decompose before the epoxy resin and has a good carbonization effect. With the addition of 7 wt.% PCS, the LOI value can achieve 31.2% and successfully pass the UL-94 test with a V-0 rating. Moreover, the cone calorimeter experiment demonstrated a noteworthy decline of 59.7% in the maximum heat release rate (pHRR), 63.7% in overall heat release (THR), and 42.3% in total smoke generation (TSP). Based on the examination of TG-FTIR and SEM findings, there is ample evidence to suggest that PCS, functioning as a phosphorus-nitrogen intumescent flame-retardant that combines three origins, has the potential to exhibit a favorable flame-retardant impact in both its gas and condensed phases.

Achieving a synergistic improvement in flame retardancy and mechanical performance remains a persistent challenge in intumescent flame-retardant (IFR) polypropylene (PP) systems. Previous studies have predominantly focused on optimizing flame retardant formulations while largely overlooking the critical role of polymer matrix chain architecture in determining the overall composite performance. In this work, three PP matrices with distinct chain architectures—homopolymer (hPP), random copolymer (rPP), and block copolymer (bPP)—were systematically investigated within an identical IFR formulation. The results reveal a dominant role of chain architecture in differentiating flame retardancy and mechanical performance, which are governed by distinct structural factors, namely melt rheological behavior and phase morphology. Specifically, bPP exhibits superior flame retardancy, as evidenced by a higher limiting oxygen index (LOI) and improved UL 94 rating, which may be associated with its higher melt viscosity and resistance to dripping during combustion. In contrast, rPP shows significantly improved mechanical performance, owing to its more homogeneous phase structure and enhanced chain mobility. These findings demonstrate that flame retardancy and mechanical properties can be effectively tuned through different structural pathways, providing a viable strategy to mitigate the conventional trade-off in IFR systems. This work highlights the importance of polymer chain architecture as a complementary design parameter alongside flame retardant additives for developing high-performance PP composites.