Bridged DOPO derivatives as flame retardants for PA6

Two novel flame retardants, based on bridged 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) were developed and evaluated as flame retardant (FR) additives in polyamide 6 (PA6) engineering plastics. The analytical evaluation of the newly developed FR/PA6 formulations indicates a good flame retardant behaviour of both bridged DOPO derivatives, achieving a V0 rating, at a thickness of 1 mm, in the UL94 vertical flammability test. Additionally, it was found that the bridged DOPO derivatives are primarily active in the gas-phase through flame inhibition as well as via increased melt-flow-drip FR mechanism.