Fire retardance and smoke suppression of polypropylene with a macromolecular intumescent flame retardant containing caged bicyclic phosphate and piperazine

Abstract

ABSTRACTA macromolecular intumescent flame retardant (FR) named PPPAP was designed and synthesized with phosphorus chloride (the acid source), 2,6,7‐trioxa‐l‐phosphabicyclo[2.2.2]‐octane‐4‐methanol (the charring agent), and anhydrous piperazine (the blowing agent). Then, it was used to prepare an intumescent flame‐retardant polypropylene (FR‐PP). The thermal stability, flame retardancy, and fire performance of the FR‐PPs were investigated. The results show that the initial decomposition temperature and char residue at 700 °C of PPPAP were 260.8 °C and 31.8%, respectively. The limiting oxygen index (LOI) value of polypropylene (PP) was enhanced with increasing PPPAP content. With the addition of 40 wt % PPPAP, the LOI value of FR‐PP was 29%, and it passed the vertical burning UL‐94 V‐0 rating. The cone calorimetry results indicate that not only the peak heat‐release rate but also the total smoke production of PP significantly decreased to 65.7 and 79.5%, respectively, with the incorporation of only 20 wt % PPPAP. The FR mechanism suggested that PPPAP played a part in both the gas and condensed phases, and the formation of the intumescent char layer during combustion was the dominant FR mechanism. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47593.