An efficient and convenient strategy toward fire safety and water resistance of polypropylene composites through design and synthesis of a novel mono-component intumescent flame retardant

A novel mono-component flame-retardant additive poly (dimethylol melamine piperazine pyrophosphate) defined as PDMPP was synthesized from formaldehyde, melamine, and piperazine pyrophosphate. Its chemical structure was well characterized by Fourier transform infrared spectroscopy, 13 C and 31 P solid-state nuclear magnetic resonance, and elemental analysis tests. PDMPP was incorporated into polypropylene (PP) matrix, and the fire-retardant performance, thermal properties, and water resistance of PP composites were investigated in detail. PP/23 wt% PDMPP composites before and after water resistance tests both achieved UL-94V-0 grade during vertical burning tests, and the limiting oxygen index was slightly declined from 26.7% to 26.3%. Small amount of PDMPP was extracted by hot water, and the weight loss percentage was 0.67% during water resistance tests. The piperazine and triazine rings in PDMPP contributed to a much better char-forming capability, and then a greatly expanded and coherent char residue was generated during combustion and exhibited excellent isolation effect. The heat release rate, carbon monoxide production, and smoke production rate of the flame-retarded PP composites before and after water resistance tests were effectively suppressed to a low level. Consequently, the introduction of PDMPP apparently improved the fire safety of PP composites as well as excellent water-resistant performance.