Lanthanum phenylphosphonate (LaHPP) was synthesized through solution reflux method with a hydrothermal reaction. The synergistic effect of decabromodiphenyl oxide (DBDPO) and LaHPP on thermal stability and flame retardancy of polycarbonate (PC) were investigated. Transmission electron microscope graphs showed that LaHPP dispersed well in the PC matrix. Thermogravimetric analyses indicated that the addition of LaHPP into PC/DBDPO composites led to better thermal stability. An appropriate content (1 wt%) of LaHPP could improve the UL94 rating (from V-2 to V-0) and limiting oxygen index value (from 32.8 to 40.5%) dramatically, and also brought an effective reduction in peak heat release rate and smoke release rate in cone calorimeter. Investigation of gaseous pyrolysis products and char residues demonstrated that LaHPP promoted the formation of more compact and solid chars, which acted as physical barriers to inhibit heat and oxygen transfer. The inside char layers also provided more space and time for DBDPO to play its flame retardant role in gaseous phases. POLYM.

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Aiming at developing a non-antimony synergistic agent of BFR and improving the high heat and smoke release of BFR due to its gaseous phase flame retardant mechanism, CeHPP was synthesized through hydrothermal reflux method and introduced into PC/DBDPO through melt blending. The morphology, chemical structure and thermal stability of CeHPP were characterized through SEM, FTIT and TG analysis, while the flame retardancy of PC/DBDPO/Sb2O3 and PC/DBDPO/CeHPP composites were compared and discussed in detail. To our delight, CeHPP showed more excellent synergistic effect with DBDPO than Sb2O3 in PC matrix. For PC/DBDPO/CeHPP (92/7/1, wt%), the sample was not ignited, the value of limited oxygen index (LOI) went up to 39.2% and it reached UL 94 V0 rating in vertical burning test, while the Izod impact strength, elongation at break and Young’s modulus were almost kept same with those of pure PC. Moreover, according to the cone calorimetry, CeHPP and DBDPO/CeHPP could efficiently suppress the heat and smoke release of PC composites, while DBDPO and DBDPO/Sb2O3 would accelerate the heat and smoke release during combustion The synergistic flame retardant mechanism verified that the char-barrier effect of CeHPP transferred the free-radical-trapping effect of BFRs from the gaseous phase to the condensed phase, which interfered the chain oxidation reaction of free-radicals and inhibiting the release and spread of gases and smoke.

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