Polyethylene flame retarded with expandable graphite and a novel intumescent additive

A novel intumescent additive was synthesized by neutralizing 3,5‐diaminobenzoic acid hydrochloride salt with ammonium dihydrogen phosphate. This compound, which melts at 257°C, decomposes concurrently to release carbon dioxide gas. The flame retardant performance of this compound as a primary fire retardant and in combination with expandable graphite (EG) was evaluated by cone calorimetry. Cone calorimeter results showed that addition of 10 wt % EG alone lowers peak heat release rate (pHRR) of carbon black‐pigmented polyethylene from 710 ± 109 to 342 ± 15 kW m−2, whereas addition of 27 wt % of the novel intumescent lowered it to 400 ± 16 kW m−2. Combinations of these two additives were able to decrease the pHRR even further. Furthermore, the novel intumescent additive reduced the flame out time from 773 ± 307 to 537 ± 69 s although all other EG containing samples increased it.