The effect of organophosphorus flame retardants on the combustion behavior and performance of poly (methyl methacrylate)

Abstract

Maintaining transparency poses a challenge in the preparation of flame-retardant poly (methyl methacrylate) (PMMA). The feasibility of preparing flame-retardant transparent PMMA by incorporating oligomeric resorcinol bis(diphenylphosphate) (liquid), 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and hexaphenoxycyclotriphosphazene (solid) as additives has been explored. The impact of the flame retardants on the processing performance, thermal stability, combustion behavior and mechanical properties of PMMA has been investigated. The presence of organophosphorus compounds does not impact the transparency of PMMA and has a significant plasticizing effect. The modified PMMA displays a UL94 V-2 rating largely due to the formation of noncombustible droplets. However, the blend exhibits lower heat resistance, modulus and strength than does unmodified PMMA. The presence of organophosphorus compounds induces a higher limiting oxygen index (LOI) and reduced heat release for combustion of the blends than observed for PMMA without relying on charring, among which DOPO has a higher flame retardant efficiency due to its higher phosphorus content and lower decomposition temperature.