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A novel fire retardant containing nitrogen and sulfur anion (triazine-sulphonate) was synthesized and then was directly intercalated into the interlayer of Mg/Al hydrotalcite (LDHs) by calcination-reconstruction manner to obtain nitrogen- and sulfur- containing flame retardant (LDH-NS) for polypropylene (PP) matrix. The microstructure and combustion properties of LDH-NS and its hybrid with PP composite (PP/LDH-NS) have been comprehensively characterized. XRD and SEM/EDS indicated that LDH-NS exhibited better dispersion than CO 3 2– intercalated LDHs (LDH-C) in the PP matrix. TGA showed that the thermal stability of PP/LDH-NS composites was enhanced. Cone calorimetry tests (CCT) illustrated that the peak heat release rate (PHRR), total heat release (THR) and total smoke release (TSR) of PP/LDH-NS composites were 255.8 kW m−2, 61.3 MJ m−2 and 205.7 m2 m−2, respectively, which exhibited declines of 69.7%, 43.1% and 75.0% compared with those of Neat PP. Furthermore, the PP/LDH-NS composites presented a limiting oxygen index (LOI) value of 28.6% and exhibited a vertical burning test (UL-94) V-1 rating at 30 wt% loading LDH-NS. All of these revealed that triazine sulfonate-modified LDHs significantly improved the fire performance of the PP matrix by increasing the char formation of PP/LDH-NS composites. Moreover, by adding the LDH-NS as filler for the PP matrix could promote the mechanical properties of PP/LDH-NS composites. The 30 wt% LDH-NS shown a significant fire retardance and thermal stability of PP matrix. Unlabelled Image • A fire retardant containing N and S anion (triazine-sulphonate) was synthesized. • Triazine-sulphonate pillared layered double hydroxides (LDH-NS) was prepared. • The 30 wt% LDH-NS shown a significant fire retardance and thermal stability of PP. • Triazine-sulphonate significantly promoted the flame retardancy of hydrotalcite to PP. [ABSTRACT FROM AUTHOR]

Ammonium polyphosphate (APP) is well known to have a synergistic action with phosphorus-based flame retardants in enhancing the flame retardant performance of matrix polymers, but the effect of APP and phosphorous-containing hydrotalcite on synergistic effect and degradation mechanism of polypropylene (PP) has not been thoroughly studied. In the present work, a synergistic flame retardant containing P 3 O 10 5− intercalated Mg/Al hydrotalcite modified by rare-earth coupling agent (W-LDH-P) and APP were prepared and used as compounded flame retardant (W-LDH-P/APP) for PP matrix. The W-LDH-P/APP and PP composites(PP/W-LDH-P/APP) possess a limiting oxygen index (LOI) value of 27.8% and achieves the V-0 standard of the flame retardant plastic. Additionally, the heat release rate (HRR), total heat release (THR) and total smoke release (TSR) for the PP/W-LDH-P/APP composites were decreased by 44.0%, 21% and 75% compared with PP/W-LDH-P. These results demonstrate that APP dramatically enhances the flame retardancy of the PP. The synergistic effect and degradation mechanism of APP and W-LDH-P are confirmed by SEM and TGA analysis. These analyses reveal that the APP and W-LDH-P promoted the formation of a more continuous and compact char layer during the burning process for PP matrix. Unlabelled Image • Hydrophobic hydrotalcite and ammonium polyphosphate were used as compounded flame retardant. • Flame-retardant mechanism of the compounded flame retardant for PP matrix was obtained. • The compounded flame retardant played an excellent effect on the flame retardancy of PP. [ABSTRACT FROM AUTHOR]