Phosphorus containing salts as flame retardants in epoxy resins and engineering plastics

Due to their good flame-retardant efficiency and minimal influence on the material properties (e.g. glass transition temperature) phosphorus containing salts are widely used as flame retardant additives. Particularly aluminum salts of dialkylphosphinic acid and aluminum hypophosphite are commercially available flame retardants for thermoplastics.1 Melamine phosphinates, phosphonates and phosphates are described as additive flame retardants for epoxy resins and often used in synergistic formulations together with melamine polyphosphate, melamine cyanurate or aluminum hydroxide.2 Due to the less thermal stability of these melamine salts they are not recommended for use in engineering plastics. Zinc complexes of these phosphorus compounds represent coordination polymers and are extremely thermally and chemically stable.3 So, they are particularly suited in synergistic formulation for use in engineering plastics. Here we describe the synthesis and structure of phosphorus co ntaining melaminium salts and coordination compounds, and their flame protection effects in polyamides and epoxy resins