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A novel char-forming agent named PEIC was designed and synthesized combining pentaerythritol octahydrogen tetraphosphate (PEPA) and tris(2-hydroxyethyl) isocyanurate. PEIC was combined with the silica-gel-microencapsulated ammonium polyphosphate (OS-MCAPP), preparing intumescent flame-retardant polypropylene (PP) composites. The results of the limiting oxygen index (LOI) show that the composite containing 30 wt % IFR with OS-MCAPP:PEIC = 2:1 presents the optimal LOI of 32.7%. Meanwhile, the cone calorimeter tests show that its peak heat release rate is 432 kW m −2 , which decreases by 62.1% compared with that of pure PP, showing a high-efficient flame retardancy. The exhibited UL-94 V-0 rating for all the composites indicates that the IFR composed of PEIC and OS-MCAPP has high-efficient flame retardancy in PP. The analysis of residue char reveals that PEIC could improve the quality of char in compactness, intumescentia, and the degree of graphitization. Further, the effect of IFR on the mechanical properties of PP composites was also evaluated and discussed.

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Cerium(IV) phosphate [CeP(IV)] was synthesised by hydrothermal synthesis and used as a synergistic agent on the flame retardancy of styrene butadiene rubber (SBR)/intumescent flame retardant (IFR) system. The IFR system mainly consisted of ammonium polyphosphate and pentaerythritol. Limiting oxygen index, UL-94 test, thermogravimetric analysis, cone calorimeter, scanning electron microscopy and microscale combustion calorimeter were used to evaluate the synergistic effects of CeP(IV). The addition of CeP(IV) to SBR/IFR composites leads to the improvement in UL-94 values of the SBR/IFR/CeP(IV) composites, and the peak of heat release rate decreases with increasing CeP(IV) content. SEM was used to analyse the morphological structure of the residue chars formed from the SBR/IFR systems with and without CeP(IV). A possible mechanism for catalysing carbonisation was discussed. The experimental results indicated that there existed a synergistic effect between CeP(IV) and IFR for the flame retardancy of SBR.

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