Polyethylene flame retarded with expandable graphite and a novel intumescent additive

Abstract

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 was evaluated by cone calorimetry. Cone calorimeter results revealed that addition of 10 wt.% expandable graphite alone lowers peak heat release rate of carbon black-pigmented polyethylene from 710 ± 109 kW m-2 to 342 ± 15 kW m-2, while 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 peak heat release rate even further. Furthermore, the novel intumescent additive reduced the flame out time from 773 ± 307 s to 537 ± 69 s although all other expandable graphite containing samples increased it.