Intercalation of a novel containing nitrogen and sulfur anion into hydrotalcite and its highly efficient flame retardant performance for polypropylene

Abstract 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 CO32– 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.