Component Ratio Effects of Hyperbranched Triazine Compound and Ammonium Polyphosphate in Flame-Retardant Polypropylene Composites

A hyperbranched derivative of triazine group (EA) was synthesized by elimination reaction between ethylenediamine and cyanuric chloride. The different-mass-ratio EA and ammonium polyphosphate (APP) were mixed and blended with polypropylene (PP) in a constant amount (25%) to prepare a series of EA/APP/PP composites. The component ratio effect of EA/APP on the flame-retardant property of the EA/APP/PP composites was investigated using the limiting oxygen index (LOI), vertical burning (UL94), and cone calorimetry tests. Results indicated that the EA/APP/PP (7.50/17.50/75.00) composite with the appropriate EA/APP mass ratio had the highest LOI, UL94 V-0 rating, lowest heat release rate, and highest residue yield. These results implied that the appropriate EA/APP mass ratio formed a better intumescent flame-retardant system and adequately exerted their synergistic effects. Furthermore, average effective combustion heat values revealed that EA/APP flame retardant possessed the gaseous-phase flame-retardant effect on PP. Residues of the EA/APP/PP composites were also investigated by scanning electron microscopy, Fourier-transform infrared, and X-ray photoelectron spectroscopy. Results demonstrated that the appropriate EA/APP mass ratio can fully interact and lock more chemical constituents containing carbon and nitrogen in the residue, thereby resulting in the formation of a dense, compact, and intumescent char layer. This char layer exerted a condensed-phase flame-retardant effect on EA/APP/PP composites. (C) 2014 Wiley Periodicals, Inc.